<%BANNER%>

Determination of Axial Pile Capacity of Prestressed Concrete Cylinder Piles


PAGE 1

DETERMINATION OF AXIAL PILE CAPA CITY OF PRESTRESSED CONCRETE CYLINDER PILES By DHURUVA BADRI A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2003

PAGE 2

Copyright 2003 by Dhuruva Badri

PAGE 3

To Mom and Dad.

PAGE 4

iv ACKNOWLEDGMENTS I am indebted, first and foremost, to Dr Michael McVay for providing me with an opportunity to attend graduate school at the Un iversity of Florida. His guidance through out the research project, along with his knowle dge and approach to problem solving has been a great plus. I would like to thank Dr. Frank To wnsend, for making graduate school a pleasurable experience. His way of teaching cl asses, and always being there to help a student with his problems will always be remembered. I would also like to than k Mr. Peter Lai with the Florida Department of Transportation (FDOT), for supporting the proj ect and taking active interest in it. I would like to thank the follo wing people for supplying me with valuable load test data, which were the heart of this project: Mr. Tom Shantz with Caltrans, Mr. Kurt Krhounek with URS, Corp, Mr. Bill Spence with Tidewater Construction Corporation (TCC), Mr. Brian Liebich with Caltrans, Mr. Mulla Mohammed with North Carolina Department of Transportation (NCDOT), Mr. Jamey Batts with NCDOT, Mr. Ashton Lawler, with Virginia Departme nt of Transportation (VDOT). I would like to express my deepest thanks to my Mother, my Father, my elder sister, Divya, my brother in la w, Madhav, my niece, Maya, and Parimala for their love, support, understanding, and Reiki that kept me going through thick and thin.

PAGE 5

v I would like to thank Mr. Hugo Soto, Mr. John Pulsifer, Mr. Juan Villegas, and Miss. Amy Guisinger and Ed Miguens with PSI, USA, for guiding me into a bright career after graduate school. Last, but certainly not least, I would lik e to express many thanks to my friends: Amit, for helping me create the UF/FDOT Data base; my room mates, Sajan, Devraj and Vivek for their cooperation; Geotechs Minh, Arvind, Lila, Dinh, Hu, Evelio, Erkan, Thai, Sangho, Sam, Mark; and friends Jas on, Sid, Archit, Sridhar, Navin, Brandy, Jayashree, and Sandeep for making my st ay in Gainesville a pleasurable one.

PAGE 6

vi TABLE OF CONTENTS Page ACKNOWLEDGMENTS.................................................................................................iv LIST OF TABLES...............................................................................................................x LIST OF FIGURES.........................................................................................................xiii ABSTRACT....................................................................................................................xvi i CHAPTER 1 INTRODUCTION........................................................................................................1 1.1 Problem or Need Statement....................................................................................1 1.2 Scope of the Research.............................................................................................1 1.3 Tasks Involved in the Project.................................................................................1 2 DATA COLLECTION.................................................................................................3 2.1 Classification of Load Test Data............................................................................3 2.1.1 Classification Based on Soil Type................................................................3 2.1.2 Classification Based on Pile Material...........................................................4 2.1.3 Classification Based on Pile Outer Diameter and Shell Thickness..............4 2.1.4 Classification Based on Plug Status.............................................................5 2.2 Current UF/FDOT Cylinder Pile Databa se Projects, and Brief Description..........5 2.2.1 St. Georges Island Bri dge Replacement Project...........................................5 2.2.2 Chesapeake Bay Bridge and Tunnel Project................................................8 2.2.3 San-Mateo Hayward Bridge.........................................................................8 2.2.4 Bridge over Oregon Inlet and Approaches on NC-12..................................9 2.2.5 Woodrow Wilson Bridge............................................................................10 2.2.6 Monitor-Merrimac Memorial Br idge-Tunnel (I-664 Bridge)....................11 2.2.7 Salinas River Bridge...................................................................................11 2.2.8 Port of Oakland...........................................................................................12 2.2.9 I-880 Oakland Site......................................................................................12 2.2.10 Santa Clara River Bridge..........................................................................13 2.2.11 Berenda Slough Bridge.............................................................................14

PAGE 7

vii 3 UF/FDOT ONLINE CYLI NDER PILE DATABASE...............................................15 3.1 Main Page.............................................................................................................15 3.1.1 Administrator User.....................................................................................16 3.1.2 Regular User...............................................................................................16 3.2 Project Page..........................................................................................................17 3.2.1 General Page...............................................................................................18 3.2.1.1 Project overview...............................................................................18 3.2.1.2 Pile description.................................................................................18 3.2.1.3 Insitu test and analysis......................................................................18 3.2.2 Load Test Page...........................................................................................19 3.2.3 Insitu Test and Soil Page............................................................................21 3.2.4 Soil Plug Page.............................................................................................24 3.2.5 Driving Page...............................................................................................25 3.2.6 Analysis and Results Page..........................................................................26 4 DATA REDUCTION.................................................................................................27 4.1 Data Reduction Using Strain Gages.....................................................................27 4.2 Data Reduction Using Davisson’s and DeBeer’s Method....................................30 4.2.1 Davisson’s Method.....................................................................................30 4.2.2 Back Computed Skin and End Bearing Values..........................................31 4.3 Comparison Between Direct and Indirect Method...............................................33 5 ESTIMATION OF SOIL PLUG................................................................................36 5.1 Formation of Soil Plug..........................................................................................36 5.1.1 The Arching Phenomenon..........................................................................37 5.1.2 Inertial Forces on the Soil Plug..................................................................38 5.1.2.1 During static loading........................................................................39 5.1.2.2 During driving..................................................................................40 5.1.3 Parametric Study – Effects of Diameter, and G-Forces.............................40 5.2 ADINA Theory and Modeling..............................................................................43 5.2.1 General Overview of the Pile Model..........................................................44 5.2.2 Material Model of the Pile..........................................................................45 5.2.3 Properties of the Pile..................................................................................45 5.2.4 Pile Formulation.........................................................................................45 5.3 ADINA-F Theory and Modeling..........................................................................46 5.3.1 General Overview of the Soil Model..........................................................46 5.3.2 Material Model of the Soil.........................................................................47 5.3.3 Boundary Condition...................................................................................47 5.3.4 Properties of the Soil Model.......................................................................47 5.3.5 Soil Formulation.........................................................................................48

PAGE 8

viii 5.4 ADINA-FSI Theory and Modeling......................................................................49 5.5 ADINA Plot..........................................................................................................50 5.6 Factors Affecting the Soil Plug.............................................................................51 5.6.1 Assumptions in Estimating the Soil Plug...................................................51 5.6.2 Unplugged Soil Velocity Profile................................................................54 5.6.3 Plugged Soil Velocity Profile.....................................................................55 5.6.4 Variation in Shell Thickness......................................................................56 5.6.5 Variation in the Outer Diameter of the Pile................................................57 5.6.6 Variation in the Rate of Penetration of the Pile..........................................58 5.6.7 Variation in Shear Strength of Soil............................................................59 5.6.8 Variation in Unit Weight of Soil................................................................60 6 SKIN FRICTION AND END BEARING CURVES.................................................62 6.1 Unit Skin Friction and Unit End Bearing Curves.................................................62 6.2 Comparison of Skin Friction and End Bearing with SPT2000.............................66 6.2 Comparison of Skin Friction and End Bearing with SPT2000.............................67 7 LOAD AND RESISTANCE FATOR DESIGN (LRFD)...........................................76 7.1 Allowable Stress Design.......................................................................................77 7.2 Load Resistance Factor Design............................................................................77 7.3 Calibration of Resistance factor for LRFD...........................................................79 7.3.1 Engineering Judgment................................................................................79 7.3.2 Fitting ASD to LRFD.................................................................................79 7.3.3 Reliability Calibration................................................................................80 7.3.3.1 Resistance bias factor.......................................................................80 7.3.3.2 Reliability index ............................................................................81 7.3.3.3 Resistance factor ..........................................................................83 7.4 Capacity Prediction...............................................................................................84 8 RESULTS AND CONCLUSION...............................................................................88 8.1 Finite Element Modeling of Soil Plug..................................................................88 8.2 Evaluating Unit Skin and Tip Resistance.............................................................89 8.3 LRFD Study..........................................................................................................90 8.4 Recommendations.................................................................................................90

PAGE 9

ix APPENDIX A DATA REDUCTION AND DATABASE.................................................................91 B ADINA ANALYSIS OF SOIL PLUG.....................................................................117 C LRFDFACTOR....................................................................................................126 LIST OF REFERENCES.................................................................................................128 BIOGRAPHICAL SKETCH...........................................................................................130

PAGE 10

x LIST OF TABLES Table page 2-1 Soil type and description............................................................................................4 2-2 Pile type classification................................................................................................4 2-3 Classification based on pile oute r diameter and shell thickness................................4 2-4 Plugged and unplugged pile s in the database.............................................................5 2-5 Current Pile Database.................................................................................................6 2-6 Soil type classification for side and tip for various projects......................................7 4-1 Contribution of skin and end bearing in DeBeer's...................................................33 4-2 Comparison between dir ect and indirect method.....................................................35 5-1 Fixed parameters in study, and values.....................................................................42 5-2 Critical g-force values with diameter.......................................................................43 5-3 Pile Properties and its variations..............................................................................45 5-4 Soil Properties and its Variation...............................................................................48 5-5 Values used for pile outer diameter parametric study..............................................58 7-1 Relationship between probability of fa ilure and reliability index for lognormal distribution (Rosenblue th and Esteva, 1972)...........................................................82 7-2 Measured vs. predicted capacity table......................................................................85 8-1 Inertia theory Vs finite element mode ling (arrows indicating whether the plugs go up or down)..............................................................................................................89 8-2 Skin friction and tip resistance equa tions (in terms of uncorrected SPT blow counts), developed using the piles in the UF/FDOT cylinder pile database............90 A-1 Current Database en try and description...................................................................91

PAGE 11

xi A-3 Data used for concrete piles in sand.........................................................................93 A-4 Data used for steel piles in sand...............................................................................93 A-6 Data used for steel piles in clay................................................................................93 A-7 Data used for concrete piles in silt...........................................................................94 A-8 Data used for the end bearing in sand......................................................................94 A-9 Data used for end bearing in silt...............................................................................94 A-10 Data used for end bearing in clay.............................................................................94 B-1 Symbols used in finite element parametric study...................................................117 B-2 Velocity of plug with variation in rati o of diameter to she ll thickness for loose sand.........................................................................................................................11 8 B-3 Velocity of plug with vari ation in ratio of diameter to shell thickness in case of dense sand..............................................................................................................118 B-4 Velocity of plug with vari ation in rate of penetration of the pile for loose sand...119 B-5 Velocity of plug with vari ation in rate of penetration of the pile for dense sand...119 B-6 Velocity of plug with variation in density of soil for loose sand...........................120 B-7 Velocity of plug with variation in density of soil for dense sand...........................120 B-8 Velocity of plug with variation of shear strength in case of loose sand.................121 B-9 Velocity of plug with variation in shear strength in case of dense sand................122 B-10 Velocity of plug with variation in shell thickness in case of loose sand................124 B-11 Velocity of plug with variation in shell thickness in case of dense sand...............124 B-12 Plug height with cha nge in t and D value...............................................................125 B-13 Plug height with change in density........................................................................125 B-14 Plug height with change in rate of penetration.......................................................125 B-15 Plug height with cha nge in shear strength..............................................................125 B-16 Plug height with vari ation in wall thickness..........................................................125 C-1 Measured Vs predicted pile capacities...................................................................126

PAGE 12

xii C-2 Statistical analysis data...........................................................................................126 C-3 LRFDfactors, for various T, and QD/QL ratios.................................................127

PAGE 13

xiii LIST OF FIGURES Figure page 3-1 Shows the MAIN page with the userna me and password fields, and a note to new users.......................................................................................................................... 15 3-2 Shows the MENU page, with the en ter data and view data fields...........................16 3-3 PROJECT page showing a list of pr ojects available on the UF/FDOT online database....................................................................................................................17 3-4 Shows the format of the General page.....................................................................19 3-5 Shows the format of the Load test page...................................................................20 3-6 Shows a plot of load displacement of the pile..........................................................20 3-7 Shows a screen shot of the strain data page.............................................................21 3-9 Plot of Cone resi stance Vs elevation........................................................................22 3-10 Screen shot showing the format for the SPT page...................................................23 3-11 Plot of blow count Vs elevation...............................................................................24 3-12 Description of the parameters used in defining the soil plug...................................24 3-13 Screen shot of the soil plug page..............................................................................25 3-14 Screen shot of the driving page................................................................................25 3-15 Screen shot of the analysis and results page............................................................26 4-1 A plot of load distribution along the pile Vs strain gage eleva tion with increment in axial load/ time for the St. George s Island Bridge Replacement project.............29 4-2 Determining capacity of pile, using Davisson’s method, for the St. Georges Island Bridge Replacement Project, Load Test-1.....................................................31 4-3 Separation of load vs. deformation plot into skin and tip........................................32 4-4 Separating skin friction and e nd bearing using DeBeer’s method...........................32

PAGE 14

xiv 4-5 Interpretation of Pile load test (High Capacity Piles, M.T Davisson).....................34 5-1 Isobars of the vertical stress with in the soil plug, showing the transition from active to passive arching..........................................................................................37 5-2 Free body diagram of soil column with in the pile during, A) Static loading, and B) Pile Driving.........................................................................................................38 5-3 Screen shot of the MathCAD file showing plug height, upward force, and downward force calculations....................................................................................41 5-4 Variation of plug height with soil plug diameter and g-forces.................................42 5-5 Isoparametric Nine Node Axisymmetric Element...................................................44 5-6 ADINA pile input, thick lines indicating contact surface........................................46 5-7 Figure showing the slip and no slip surfaces along the various boundaries............47 5-8 Showing an ADINA-F soil mesh.............................................................................48 5-9 Contact Surface Geometry.......................................................................................50 5-10 ADINA Plots ...........................................................................................................50 5-11 Flow chart indicating the various steps in the analysis of the plug..........................51 5-12 Velocity profile with in the finite element model....................................................52 5-13 Plot showing variation in velocity with in the pile with change in plug height.......54 5-14 Velocity profile with in cylinder pileunplugged condition....................................55 5-15 Velocity profile with in cylinder pileplugged condition........................................56 5-16 Plot showing variation of shell thickness with height of soil plug...........................57 5-17 Plot showing variation in the soil plug with change in outer diameter....................58 5-18 Variation in Rate of Penetration...............................................................................59 5-20 Variation in Unit Weight of Soil..............................................................................61 6-1 Skin friction (tsf) Vs N (uncorre cted) for concrete piles in sand.............................63 6-2 Skin friction (tsf) Vs N (unc orrected) for steel piles in sand...................................63 6-3 Skin friction (tsf) Vs N (uncorre cted) for concrete piles in clay..............................64

PAGE 15

xv 6-4 Skin friction (tsf) Vs N (unco rrected) for steel piles in clay....................................64 6-5 Skin friction (tsf) Vs N (uncorre cted) for concrete piles in silts..............................65 6-6 End bearing (tsf) Vs N (uncorrected) in Sands........................................................65 6-7 End bearing (tsf) Vs N (uncorrected) in Clays.........................................................66 6-8 End bearing (tsf) Vs N (uncorrected) for silts..........................................................66 6-9 Comparison of various de signs used for computing un it skin friction in clays.......68 6-10 Comparison of various de signs used for computing un it skin friction in silts.........69 6-11 Comparison of various de signs used for computing un it skin friction in sands......70 6-12 Comparison of various de signs used for computing un it end bearing in clays........71 6-13 Comparison of various de signs used for computing un it end bearing in silts..........72 6-14 Comparison of various de signs used for computing un it end bearing in sands.......73 6-15 Comparison of unit skin friction vs. SPT N values, for various soil types, and pile materials, in cas e of cylinder piles....................................................................74 6-16 Comparison of unit end bearing vs. SPT N values, for various soils, in case of cylinder piles............................................................................................................75 7-1 Failure region and the reliability ...........................................................................82 7-2 Resistance Factor vs. Dead to Live Lo ad Ratio, Large Diameter Cylinder Pile with ring area............................................................................................................86 7-3 Resistance Factor vs. Dead to Live Lo ad Ratio, Large Diameter Cylinder Pile with ring area............................................................................................................86 7-4 Comparison of measured vs. predicted capacities...................................................87 A-1 St. Georges Island Bridge Replacement Project LT-1.............................................95 A-2 St. Georges Island Bridge Replacement Project, LT-4............................................96 A-3 Chesapeake Bay LT-1..............................................................................................97 A-4 Chesapeake Bay LT-2..............................................................................................98 A-5 Chesapeake Bay LT-6..............................................................................................99 A-6 San Mateo Hayward Bridge-A...............................................................................100

PAGE 16

xvi A-7 I-664 Bridge Test-4................................................................................................101 A-8 I-664 Bridge Test-7................................................................................................102 A-9 Woodrow Wilson Bridge-C...................................................................................103 A-10 Woodrow Wilson Bridge-F....................................................................................104 A-11 Woodrow Wilson Bridge-I.....................................................................................105 A-12 Oregon Inlet............................................................................................................10 6 A-13 Salinas River Bridge...............................................................................................107 A-14 Port of Oakland Bridge 27NC................................................................................108 A-15 Port of Oakland Bridge 10NC................................................................................109 A-16 Port of Oakland Bridge 17NC................................................................................110 A-17 Port of Oakland Bridge 31NC................................................................................111 A-18 I-880 Bridge 3H.....................................................................................................112 A-19 I-880 Bridge 3C......................................................................................................113 A-20 Santa Clara Rive r Bridge Pier-7.............................................................................114 A-21 Santa Clara Rive r Bridge Pier-13...........................................................................115 A-22 Santa Clara Rive r Bridge Pier-13...........................................................................116

PAGE 17

xvii Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science DETERMINATION OF AXIAL PILE CAPA CITY OF PRESTRESSED CONCRETE CYLINDER PILES By Dhuruva Badri December 2003 Chair: Michael McVay. Major Department: Civil and Coastal Engineering. Recognizing the numerous advantages of la rge diameter cylinder piles, the Florida Department of Transportation (F DOT) and its contractors have been considering their use in place of smaller diameter p iles, and drilled shafts. Thirty-six load test data on large diameter cylinder piles were collected nationw ide. The data were then separated based on soil type, pile material (concrete/steel), pile geometry (shell thic kness/ outer diameter), and the state of plug (plugged/unplugged), a nd then placed into the UF/ FDOT cylinder pile database. These load test data were then reduced in to unit skin friction, and unit end bearing vs. SPT N values, for different soil types, a nd pile material. These results would be used in updating the axial pile capacity assessment software, S.P.T 97. Further, an LRFD (i.e., Load Resistance and Factor Design) study was pe rformed in order to check the reliability of the design.

PAGE 18

xviii During pile installation, soil enters the a nnular region of the pile tip forming a column of soil. The length of this column has to be estimated in the drivability analysis, and the state of plug has to be determined for calculating the end bearing. The pile installation process was modele d using the finite element, and a parametric study was performed to study the factors impac ting the formation of the soil plug.

PAGE 19

1 CHAPTER 1 INTRODUCTION The research project consists of determini ng the axial pile capacity of prestressed concrete cylinder piles, for the Florid a Department of Transportation (FDOT). 1.1 Problem or Need Statement The research was performed considering th e numerous advantages of using a large diameter cylinder pile as compared to several smaller piles, or drilled shafts. For instance, the large diameter cylinder pile has a larger moment of inertia as compared to a smaller diameter pile, and will resist large lateral load s (i.e., ship impacts). Also, the cylinder pile will provide larger skin and tip resistance in sands, and clays, as compared to a similar size drilled shaft (i.e., similar moment of inertia), due to its method of installation. In addition, the results of the research would be used to update the axial pile capacity assessment software, SPT97, to include prestressed concrete cylinder piles. 1.2 Scope of the Research The scope of this research involved th e engineering knowledge of deep foundation analysis and design, databases, F.E.M (i .e., Finite Element Method) theory, and application software ADINA (i.e., Automa tic Dynamic Incremental Non-Linear Analysis). 1.3 Tasks Involved in the Project The various tasks involved were as follows: 1. Collecting cylinder pile load test data: In order to collect cylinder pile load test data, over eighty Geotechnical companies, and Federal Agencies, were contacted nation-wide, and around the world. A total of thirty-six, load test data on large

PAGE 20

2 diameter cylinder piles were collected. A list of companies contacted, and data obtained are provided in th e forthcoming chapters. 2. Developing a database base d on pile dimension, and soil type: The data in the database was separated based on the soil type pile material, outer diameter of the pile, shell thickness of the pile, and th e state of plug within the pile (i.e., plugged/unplugged). An online database was th en built to store and share data with other researchers. The knowledge of Micr osoft Access, ASP (i.e., Active Server Protocol), SQL (i.e., Structured Query La nguage) and JavaScript was used in the design of this database. 3. Evaluating Unit Skin and Tip Resistance: The results of the load test were reduced into unit skin friction, and unit tip resistan ce, using data from strain gages, and a combination of Davisson’s method, and deB eer’s method. These results were then correlated against uncorrected SPT blow counts (N), for diff erent soil types and pile material. The results of this test we re then compared w ith the present design, used in SPT97. 4. Determination of Soil Plug heights, what im pacts it and its effects on soil capacity: The effect of inertia of the soil plug on its height was studied. The knowledge of F.E.M (i.e., Finite Element Method), and application software ADINA (i.e., Automatic Dynamic Incremental Non-Linear Analysis) was used in modeling the soil plug response. A parametric study was th en carried out to determine the factors impacting it and their extents. 5. Evaluating bias (i.e., measured over predic ted), COV (i.e., coefficient of standard deviation) and determining the LRFD (i.e., Load Resistance and factor design).

PAGE 21

3 CHAPTER 2 DATA COLLECTION In order to collect static load test data on large diameter cylinder pile over eighty geotechnical companies, and federal agencies were contacted nati on wide and around the world. All projects were undertaken on behalf of federal Agencies like, Florida Department of Transporta tion (FDOT), California Depa rtment of Transportation (CALTRANS), Virginia Depa rtment of Transportation (VDOT), North Carolina Department of Transportation (NCDOT) a nd Maryland State Highway Administration (MSHA). All Static Axial Load Testing procedures were in general conformance with ASTM D 1143-81 (1994). 2.1 Classification of Load Test Data The data from the load test were placed in the database, and then classified based on: 1. Soil type. 2. Material of the Pile. 3. Outer diameter, and shell thickness of the pile. 4. State of the soil plug. 2.1.1 Classification Based on Soil Type Based on the SPT97 program, the soil was classi fied into four types. Table 2-1 lists the soil types, and a brief description.

PAGE 22

4 Table 2-1. Soil type and description Soil Type Description Number 1 Plastic Clay 13 2 Clay-silt-sand mixtures, very silty sand, silts and marls 11 3 Clean Sands 18 4 Soft Limestone, very shelly sands 2 2.1.2 Classification Based on Pile Material Based on the material of the pile, the piles were classified into concrete, and steel piles. Table 2-2, lists the number of piles of each type, in the database. Table 2-2. Pile type classification. Material Type Description Number 1 Concrete 27 2 Steel 9 2.1.3 Classification Based on Pile Outer Diameter and Shell Thickness Piles were classified based on their outer diameter, and sh ell thickness, to evaluate the effect of geometry on unit skin friction, unit end bearing, and th e formation of soil plug. Table 2-3, lists the number of piles of various diameters, and shell thickness. Table 2-3. Classification based on pile outer diameter and shell thickness. Outer Diameter Number Shell Thickness Number 84-inch 1 8-inch 4 72-inch 2 6.9-inch 2 66-inch 3 6-inch 7 54-inch 19 5-inch 10 42-inch 10 2-inch to 1-inch 5 36-inch 1 >1-inch 8

PAGE 23

5 2.1.4 Classification Based on Plug Status Based on the type of plug, the piles were classified as plugged piles, and unplugged piles. A plugged pile was defined as one in wh ich, the soil within the pile had no relative movement with respect to the pile. All other piles were defi ned as unplugged piles. Table 2-4, lists the number of plugged piles, and unplugged piles in the database. Table 2-4. Plugged and unplugged piles in the database. Plug Status Number Plugged 11 Unplugged 25 2.2 Current UF/FDOT Cylinder Pile Databa se Projects, and Brief Description Table 2-5 lists thirty-six piles, from el even different projects, in the current UF/FDOT database, along with a brief descrip tion of the outer diameter, shell thickness, pile material, major soil type, and the number of tests data available from this project. A brief description of each follows. 2.2.1 St. Georges Island Bridge Replacement Project The Bridge was built for the Florida Depa rtment of Transportation (FDOT) by the team of Boh Brothers Constr uction, and Jacob Civil, Inc; in Apalachicola Bay over inter coastal waters. Applied Foundati on Testing, Inc performed the lo ad test. The piles tested were spuncast post tensioned concrete cylinder piles with an outer diameter of 54-inches, shell thickness of 8-inches and lengths of 80-ft. The prevailing soil type at the location was very loose silty sand, above a layer of dense to very dense silty sand, underlain by a la yer of limestone. The piles were driven to refusal in the limestone layer. Additional deta ils on the soils, pile, and installation were available from the geotechnical records of W illiams Earth Sciences, Inc. (WES). Insitu

PAGE 24

6 data from both CPT (i.e., Cone Penetrati on Test) and SPT (i.e., Standard Penetration Test) are available for this particular project. Table 2-5. Current Pile Database Pile Description Project Name Outer Diameter Shell Thickness Pile Material Major Soil Type Number of Tests 1 St. Georges Island Bridge Replacement Project, FL 54-inch 8-inch Post Tensioned Concrete Silty Sands over Limestone 4 2 Chesapeake Bay Bridge and Tunnel Project, VA 54-inch, 66-inch 6-inch Prestressed Concrete Dense sands 6 3 San-Mateo Hayward Bridge, CA 42-inch 6.9-inch Concrete Silty Clays 2 4 Oregon Inlet, NC 66-inch 6-inch Concrete Silty Fine Sands 1 5 Woodrow-Wilson Bridge, MD 54-inch, 42-inch and 36inch 1-inch Steel Silty Sands 3 6 North and South Trestle, I-664 Bridge, VA 54-inch 5-inch Concrete Silts and Sands 10 7 Salinas River Bridge, CA 72-inch .75-inch Steel Mixed 1 8 Port of Oakland, CA 42-inch .625-inch, .75-inch Steel Clays 4 9 I-880 Oakland, CA 42-inch .75-inch Steel Clays 2 10 Santa Clara River Bridge, CA 84-inch, 72-inch 1.5-inch, 1.74-inch Steel Sands 2 11 Berenda Slough Br, CA 42-inch .625-inch Steel Sands 1 Total 36 Also, the soil at the side and tip were identified for correlation purpose (Chapter-4, and Chapter-6), from the logs of SPT boring data as shown in table 2-6.

PAGE 25

7 Table 2-6. Soil type classification for side and tip for various projects. Soil Type For Sno Project Name Skin Friction End Bearing Insitu Test 1 St. Georges Island Projec t Sand Limestone SPT/CPT 2 St. Georges Island Projec t Sand Limestone SPT/CPT 3 St. Georges Island Projec t Sand Limestone SPT/CPT 4 St. Georges Island Projec t Sand Limestone SPT/CPT 5 Chesapeake Bay Bridge Silt Silt CPT/SPT 6 Chesapeake Bay Bridge Silt Silt CPT/SPT 7 Chesapeake Bay Bridge Silt Silt CPT/SPT 8 Chesapeake Bay Bridge Sand Sand CPT/SPT 9 Chesapeake Bay Bridge Sand Sand CPT/SPT 10 Chesapeake Bay Bridge Sand Sand SPT 11 San Mateo Hayward Bridge Silt Silt SPT 12 San Mateo Hayward Bridge Silt Silt SPT 13 Oregon Inlet Silt Silt CPT/SPT 14 I-664 Bridge North Clay Clay SPT 15 South Test-4 Sands Sands SPT 16 South Test-5 Sands Sands SPT 17 South Test-6 Sands Sands SPT 18 South Test-10 Sands Sands SPT 19 South Test-11 Sands Sands SPT 20 South Test-12 Sands Sands SPT 21 South Test-13 Sands Sands SPT 22 South Test-14 Sands Sands SPT 23 Woodrow Wilson Bridge Sands Clays SPT 24 Woodrow Wilson Bridge Sands Clays SPT 25 Woodrow Wilson Bridge Sands Clays SPT 26 Salinas River Bridge Clays Clays SPT 27 Port Of Oakland 27NC Clay Clays SPT 28 Port Of Oakland 17NC1 Clay Clays SPT 29 Port Of Oakland 10NC1 Clay Clays SPT 30 Port Of Oakland 31NC Clay Clays SPT 31 I-880 Oakland Site 3C Clay Clays SPT 32 I-880 Oakland Site 3H Clay Clay SPT 33 Santa Clara River Bridge 13Sand Sands SPT 34 Santa Clara River Bridge 7 Sand Sands SPT 35 Berenda Slough Br 4 Silts Silts SPT Data for four compression load test were available from this project. Reaction load was applied through frame-supported wate r filled barges. Four pipe piles supported

PAGE 26

8 this weighted box apparatus. Loading rate was generally governed by filling the barges with water. All test piles were instrume nted with embedded strain gages and a toe accelerometer. The piles at this project did not form a soil plug. 2.2.2 Chesapeake Bay Bridge and Tunnel Project The load testing was performed as a part of building a parallel crossing to the already existing Chesapeake Bay Bridge. The CBBTD (i.e., Chesapeake Bay Bridge and Tunnel District) contracted w ith Tidewater Construction Co rporation (TCC), to perform the construction, installation, a nd loading of the test piles. Bayshore Concrete Products, Inc., a subcontractor to TCC, fabricated the piles. Load test information for six prestressed concrete cylinder piles is available from this project. Fifty-four inch diameter piles were used at TP-1, TP-2, TP-3, and TP-6, whereas 66-inch diameter piles were used at TP-4 and TP-5. All piles were 6-inch thick. The lengths of these piles varied from 128-ft at site TP-6 to 2 04-ft at site TP-5. The prevailing soil at location TP-1, TP-2 and TP-6 was silt and clay with small amounts of sand; and at location TP-3, TP-4 a nd TP-5 the prevailing soil was dense gray sand with small amounts of silt and clay. In situ data from both SPT and CPT are available for this project. Piles TP-1, TP-4, TP-5 and TP-6 formed soil plugs, the upper surface of the plugs formed in these piles were at depths of 13-ft 1-ft, 8-ft, and 6-ft below mudline. Piles TP2 and TP-3 did not form any soil plug. 2.2.3 San-Mateo Hayward Bridge The San Mateo Bridge, also called the Sa n Mateo Hayward Bridge, runs roughly east west so as to cross the lower part of San Francisco Bay. It ca rries California State Highway 92 so as to join Haywood, I-580 and I-880 on the east side of the bay with

PAGE 27

9 Foster City, San Mateo and US101 on the west side. The scope of the project involved building a new 60-foot trestle on the north side of the already existing trestle. CALTRANS performed load test on two large diameter prestressed concrete cylinder piles. The piles had an outer diameter of 42-inch, and a shell thickness of 6.9inch. The length of the pile was 42.25-meters at site A, and 40.8-meters at site B. SPT data are available for this project. The closest boring to Site A, indicates layers of very soft silty clay down to an elevation of –55-feet, followed by interbedded layers of compact silty clay, and compact sand down to the specified tip eleva tion of the pile. The closest boring in the vicinity of Site B indicates very soft si lty clay down to an elevation of –20-feet, followed by interbedded layers of stiff silty clay, and compact sand down to the specified tip elevation of the pile. 2.2.4 Bridge over Oregon Inlet and Approaches on NC-12 The bridge over Oregon Inlet and approach es on NC-12 is located on the south side of Oregon Inlet’s Bonner Bridge in Dare County, North Carolina. The. North Carolina Department of Tr ansportation (NCDOT) contracted with Hardway Company, and S&ME Environmenta l Services for Pile and Test Boring contracts. The test consisted of Static Axial Comp ressive load test on a 66-inch diameter concrete cylinder pile with a shell thickness of 6-inch, and a length of 131.5-feet. Insitu data from both SPT, a nd CPT are available for this project. The soil profile consists of clayey silt to a depth of –12-mete rs, and layers of sand and sandy silt till the tip elevation. The pile did not form a soil plug.

PAGE 28

10 2.2.5 Woodrow Wilson Bridge The Woodrow Wilson Bridge is located about 6 miles south of Washington DC Metropolitan area; it is approximately at the mid point of I-95, one of the busiest east coast interstate highways. The load testing for the project was pl anned and implemented by Potomac Crossing Consultants (PCC), a joint venture of UR S Corporation, Parsons-Brinkerhoff, and Rummel-Klepper-Kahl, in the capacity of the General Engineering Consultant (GEC). All work was authorized by the Maryland St ate Highway Administ ration (MSHA) in conjunction with the Federal Highway Admi nistration (FHWA) and was performed in association with Section Design Consultant (SDC), Parson Transportation Group (PTG) and Mueser Rutledge Consulting Engineers (MRCE). Three axial static load tests are availabl e from this project and are identified as PL-1, PL-2 and PL-3. PL-1 was located near th e eastern bascule pier in the main shipping channel of the Potomac River, PL-2 was locat ed to the west of the secondary channel near the eastern abutment, and PL-3 was locat ed on land in Jones Point Park, Virginia. The site lies in the Atlantic Coastal Plain, which consists of a wide belt of sedimentary deposits overlying the crystallin e bedrock of the Piedmont, which outcrops to the northwest. These mate rials, known collectively as the Potomac Group, consist of dense sands and gravels with va riable fractions of fines, a nd very stiff to hard, highly overconsolidated clays. Although these clays ar e very hard, the pres ence of slickensides often reduces the overall shear strength of the soil mass. These clays vary in mineral composition, resulting in vari able potential for expansion. Insitu data from SPT are available for this project.

PAGE 29

11 The Potomac River is a tidal river with a mean water elevatio n of +1 feet above sea level, fluctuating between Mean Low Water of elevation –1-feet and Mean High Water of elevation +3-feet. The three steel piles at PL-1, PL-2, a nd PL-3 had outer diameters of 54-inch, 42inch, and 36-inch and, lengths of 164-ft, 125ft, and 96-ft respectively. All piles had a shell thickness of 1-inch. None of the piles formed a soil plug. 2.2.6 Monitor-Merrimac Memorial Bridge-Tunnel (I-664 Bridge) The Monitor-Merrimac Memorial Bridge -Tunnel connects I-664 in Hampton to I664/I-264 Chesapeake. The Virginia Departme nt of Transportation (VDOT) contracted with STS Consultants Ltd of Virginia for conducting the various load tests. Static axial load test were performed on 54-inch diameter prestressed concrete cylinder piles with a wall thickne ss of 5-inch and lengths vary ing from 47.9-ft at Test-4 to 145.1-ft at Test-10. A total of ten load test data is available from this project, one on the north side and nine on the south side of the bridge. The general soil profile at the site indicates interbedded layers of soft black silt, very soft gray silty clay, green-gray sandy silt s, and sandy clays. These soils comprise the Yorktown formation, which exhibits a signifi cant amount of soil fr eeze or setup. Insitu data from SPT are available for this project. None of the piles formed a soil plug. 2.2.7 Salinas River Bridge The Salinas River Bridge is located on SR101, over the Salinas River near Soledad, California. Data on one 72-inch diam eter, .75-inch thick steel pipe pile is available from this project. The pile was in stalled specifically for testing (and not to be

PAGE 30

12 incorporated into the bridge structure) by the personnel fr om the Office of Structural Foundation, Geotechnical Suppor t Branch of Caltrans. Boring B-13 is the closest boring to the test pile, located about 90 feet away. Boring B-13 shows layers of loose to compact sand from the ground surface elevation of 7-ft to –32-ft. The sand layers are underlain by a layer of soft clay to an elevation –52-ft, and layers of loose silt to an elevation –70 ft Below these layers to an elevation of –103 ft are layers of soft to sti ff clay. From elevation –103 ft to –121 ft is a layer of dense sand. Insitu data from SPT are available for this project. The pile did not form an internal soil plug during installation. Measurements taken upon completion of driving showed the t op of soil plug to be 13 feet below ground surface elevation. The difference in elevation between the top of soil plug and original ground elevation is likely a resu lt of vibration-induced settle ment of the soil inside the pile, or result of the soft clay being disp laced by the denser material inside the pile. 2.2.8 Port of Oakland Four static axial load te sts on 42-inch diameter, cast-i n-steel shell concrete piles were conducted at the Port of Oakland Connector Viaduct and Maritime On and Off Ramps. Members of the Geotechnical Support Bran ch of Caltrans conducted these tests. Subsurface conditions at the three site s can be estimated based upon fieldwork completed by Caltrans. Soil encountered at all of the test locations consisted of three distinct materials: fill, Young Bay Mud de posit, and Old Bay Mud deposits. Throughout the jobsite the elevations separating thes e four materials varied considerably. 2.2.9 I-880 Oakland Site The load test site is located at the west end of the West Grand Avenue aerial structure, approximately 1100 f eet east of the San Franci sco Oakland Bay Bridge Toll

PAGE 31

13 Plaza and north of the existing west bound lanes of I-80, along the margin of the San Francisco Bay. Caltrans carried out the test in an effort to better understand issues associated with the use of large diameter stee l piles. The study consisted of installing two 42-inch diameter and .75-inch thick steel cylinder piles. Soils at these various test sites consis ts of Artificial Fill; Young Bay Mud an unconsolidated Holocene estuarine deposit; Me rritt Sands – a Pleistocene non-marine deposit (member of the San Antonio formation) ; and Old Bay Mud – an older Pleistocene marine deposit also referred to as Yerba Bu ena Mud. Depth to bedrock is estimated to vary from –500 ft to –550 ft. The piles at Site 3 were 120 ft in le ngth. Due to transportation and handling constraints, driving occurred in two phases. The first portion of pile installation consisted of installing a nominal 80 ft long pile spliced together from two 40 ft section in a nearby fabrication yard. The remaining 40 ft section of the pile was suspended vertically, then welded to the portion of the pile previously installed. Piles were then driven to the specified tip elevation. At the completion of installation, the plug was measured at 3.25 ft below the original ground in case of Pile 3C and 10 ft in case of Pile 3H. 2.2.10 Santa Clara River Bridge The load test program was a part of th e Santa Clara River Bridge replacement, on the I-5 and I-5/SR-126 road separation (M agic Mountain Parkway) in Los Angeles County at Santa Clarita. The project included the installati on of two large diameter castin-steel-shell (CISS) piles at location Pier 13 and Pier 7. Th e piles at Pier 13 and Pier 7 were 72-inch diameter, 1.5-inch thick a nd 84-inch diameter and 1.74-inch thick respectively. Personnel from the Foundation Te sting Branch (FTB), of the Office of

PAGE 32

14 Geotechnical Support (Caltrans) conducted two compressive stat ic axial load tests each at Pier 13 and Pier 7. The subsurface location at pier 13 as inferred from Boring B1-99 indicates the presence of alternating layers of very stiff cl ay and dense sand with silt and gravels. At deeper depths, the boring encountered very dense layers of sands and gravels. The subsurface location at Pier 7 location as infe rred from Boring 00-3 indicates the presence of alternating layers of medium to very dense silts and sands with very stiff clays. At deeper depth, the boring encountered very dense layers of sands and gravels over cemented silty sands. Insitu data from SPT are available for this project. 2.2.11 Berenda Slough Bridge The Berenda Slough Bridge is located on Route 220 in Madera County near Chowchilla. The project include d the installation of 42-inch diameter, .625-inch thick cast-in-steel-shell pile, by the personnel fr om the Foundation Testing and Instrumentation Branch of the Division of Structural Foundations. Boring 98-5 indicates layers of sand, silty sand, and silt present at the test pile site. Insitu data from SPT are available for this project.

PAGE 33

15 CHAPTER 3 UF/FDOT ONLINE CYLINDER PILE DATABASE The online UF/FDOT large diameter cylinde r pile database was developed, as a joint effort with researchers around the world on large diameter driven piles. The main purpose of the database was to share the exis ting load test data, and get more data. The database was built on a Microsoft Access, ht ml (i.e., HyperText Markup Language), ASP (i.e., Active Server Pages) and JavaScript platform. 3.1 Main Page The MAIN page, grants the user permi ssion to enter the database. Based on the type of username and password, the user is id entified as an administrator, or a regular user, and given permission to access the various pages within the database. Figure 3-1. Shows the MAIN page with the us ername and password fields, and a note to new users.

PAGE 34

16 3.1.1 Administrator User All users are given access from the MAIN page, into the MENU page. Once at the MENU page, an administrator user is given access to both data en try, and viewing the already existing data. Figure 3-2. Shows the MENU page, with th e enter data and view data fields. 3.1.2 Regular User A regular user has rights only to view the data (i.e., VIEW DATA page), and would be prompted to enter the administrative username and password to enter the ENTER DATA page. Once the user enters the VIEW DATA pa ge, he/she would be taken to the PROJECTS page. The PROJECTS page, lists all the projects in the database, the user can view the details of the list ed project from there on. The various pages within the ENTER DATA and VIEW DATA are discussed simultaneously, as they have the same formats.

PAGE 35

17 3.2 Project Page The PROJECT page lists the names of all the projects in the database, in three columns. The data for each project is presen ted in six sections (p ages). An option of navigating back to the list of projects (PROJECT page) is available from each of these pages. The six pages describing each project are as follows: 1. General page. 2. Load test page. 3. Insitu test and soil page. 4. Soil plug page. 5. Driving page. 6. Analysis and results page. A brief description of each page follows. Figure 3-3. PROJECT page showing a list of projects available on the UF/FDOT online database.

PAGE 36

18 3.2.1 General Page The GENERAL page summarizes the enti re project information, and can be classified into: 1. Project Overview. 2. Pile Description. 3. Insitu test and analysis. 3.2.1.1 Project overview Information falling under this category in cludes project name, project number, submitting company, submitting engineer, and co mments. These give a general overview of the project. 3.2.1.2 Pile description Information describing the pile such as out er diameter, shell thickness, total length of pile, and pile material fall under this category. 3.2.1.3 Insitu test and analysis Types of insitu test available from the proj ect, pile top elevation, pile tip elevation, water elevation, mudline elevation, embedded le ngth of the pile, major soil type, and plug status fall unde r this category. The insitu test data could be from CPT, SPT, or CPT/SPT (both CPT and SPT). In case of CPT/SPT, the insitu test and soil page would be CPT test by default, with an option of viewing or entering SPT data. This has been further described in section 3.2.3. The two options for the plug status are pl ugged, and unplugged; these have been created as drop down window in the data entry page.

PAGE 37

19 Figure 3-4. Shows the format of the General page. 3.2.2 Load Test Page The three columns in this plot are Time (minutes), Force (Tons), and displacement (inch). The view graph page us es the JavaScript applicati on in plotting the two columns force and displacement (Figure 3-6). The Go to Strain Data link at the top of th e page tabulates the da ta from the strain gages. The three columns on the STRAIN DATA page are the Time (min), Depth of the strain gage from the top of the pile (ft), a nd the force (Tons) transfe rred to pile at that depth (calculated using strain gage data). The view graph option plots the load along the length of the pile. The Go to Main Data link br ings the user back to the main load test page.

PAGE 38

20 Figure 3-5. Shows the format of the Load test page. Figure 3-6. Shows a plot of load displacement of the pile.

PAGE 39

21 Figure 3-7. Shows a screen shot of the strain data page. 3.2.3 Insitu Test and Soil Page Based on the insitu test information on the Ge neral page, the type of insitu test page will open. In case of CPT test, the page opens up with six columns namely elevation, depth, soil type, cone resistance, friction resi stance, and friction ratio. The page has an option of plotting a graph of c one resistance vs. elevation, and skin friction vs. resistance at the bottom of the page.

PAGE 40

22 Figure 3-8. Screen shot showing the insitu test page for CPT data. Figure 3-9. Plot of Cone re sistance Vs elevation.

PAGE 41

23 In case of SPT test the page has four columns: elevation, depth, soil type and uncorrected blow count (N). An option of plo tting blow count vs. elev ation is available at the bottom of the page. In case there are both CPT and SPT data av ailable from the test, the insitu data page opens up with CPT data, and an option to go to SPT data. Figure 3-10. Screen shot showing the format for the SPT page.

PAGE 42

24 Figure 3-11. Plot of bl ow count Vs elevation. 3.2.4 Soil Plug Page The soil plug page has information on the status of the plug (plugged or unplugged), plug height from the mudline (hm), plug height from the tip (ht), type of soil at the tip, and the soil type at the mudline. Mudline hm Soil Plug ht Figure 3-12. Description of the parame ters used in defining the soil plug.

PAGE 43

25 Figure 3-13. Screen shot of the soil plug page. 3.2.5 Driving Page The driving page has information such as the type of hammer, weight, energy, pre bored depth, last blow, end of dr iving, and start of re-strike on it. Figure 3-14. Screen shot of the driving page.

PAGE 44

26 3.2.6 Analysis and Results Page The analysis and results page has informa tion on the assumptions used in the data reduction. Results of the analysis such as skin friction, and end bearing are also presented. Figure 3-15. Screen shot of the analysis and results page.

PAGE 45

27 CHAPTER 4 DATA REDUCTION Data from the UF/FDOT cyli nder pile database were se parated into skin friction, and tip resistance. This data had already been classified based on ma jor soil type (insitu test data), pile material, geometry of the pi le (i.e., outer diameter, and shell thickness), and the plug status (dis cussed in section 2-1). The two methods used in separating the load test data into unit skin friction and tip resistance were, 1. Direct Method: By reducing strain gage da ta from instrumented cylinder piles. 2. Indirect Method: By reducing load Vs deflection data using Davisson’s and deBeer’s Method. 4.1 Data Reduction Using Strain Gages Strain gages are either surface mounted, or embedment type, and are installed in/on the pile, in order to determine the ultimate sk in friction value in each of the soil strata. As an axial load is applied to the pile, some percentage of the load is transferred to the surrounding soil; beginning in the uppermost st ratum, and the remaining percentage of the load is transmitted down to the lower stratu m, through the pile. As the applied load is increased, a greater percentage of the load is transferre d to the lower strata and, eventually, to the pile tip. The unit skin friction value along any porti on of the pile is calculated as the difference in the load between two adjacent st rain gages divided by the surface area of the pile between the gages, that is,

PAGE 46

28 f = (P1-P2) / (C*L1-2) Eq.4-1 f = Unit Skin Friction (tsf) P1 = Load from strain gage 1 (Tons) P2 = Load from strain gage 2 (Tons) C = Circumference of the pile (ft) L1-2 = Length between gages (feet) The calculation of the load from a strain gage is derived from Hooke’s law, and algebraic substitution utilizing the basic principals from mechanics of materials, stress and strain. For the initial straight line porti on of stress-strain diagram, the stress is directly proportional to the strain; that is, = E Eq.4-2 = Stress (ksi) E = Modulus of Elasticity (ksi) = strain (in/in) The stress in a structural member is obt ained by dividing the magnitude of the load by the cross sectional area, = P/A Eq.4-3 = Stress (ksi) P = Load (kips) A = Cross-sectional area (sq-in) A structural member responds to stress by straining, which is the ratio of total deformation of the member to the total length of the member, or: = /L Eq.4-4

PAGE 47

29 = Strain (in/in) = Total deformation under load (in) L = Length of member (in) Substituting P/A for in Hooke’s Law (Equation 2) results in: P / A = E Or, P = E * A Eq.4-5 The elastic modulus and the cross-sectional area of th e pile are known, and that the strain has been determined from the re lationship between fre quency and deformation from the strain gage, simple multiplication retu rns the load in the pile at the location of the strain gage. The unit skin friction value can then be determined from Equation 4-1 where the difference in load (P1-P2) be tween any two levels of strain gages is divided by the perimeter area of the pile between them (i.e., C L1-2). Load Desipation Curve -70 -60 -50 -40 -30 -20 -10 0 020040060080010001200 Load ( ki p s ) Depth (ft) 5000 sec 10000sec 15000 sec 20000 sec 25000sec 30000 sec Figure 4-1. A plot of load di stribution along the pile Vs st rain gage elevation with increment in axial load/ time for th e St. Georges Island Bridge Replacement project.

PAGE 48

30 Data from strain gages is available from four load tests performed at St. Georges Island Bridge Replacement Project, and thre e tests performed at the Woodrow Wilson Bridge Project. 4.2 Data Reduction Using Davisson’s and DeBeer’s Method To reduce unit skin friction and end beari ng in the absence of data from strain gages, the Davisson’s method was used in conjunction with DeBeer’s method. 4.2.1 Davisson’s Method FDOT recommends (also recommen ded by AASHTO and FHWA) that compressive axial load test data be eval uated by the method proposed by Davisson. For piles greater than 24 inches in diameter, the ultima te load that a pile can resist is that load which produces a movement of the pile head equal to: S = + D / 30 Eq.4-6 S = Pile head movement (inch) = Elastic deformation or (P L) / (A E) P = Test load (kips) L = Pile length (inch) A = Cross-sectional area of the pile E = Modulus of elasticity of the pile material (ksi) D = Pile diameter (inch) A pile of length (L), area (A), and Y oung’s Modulus (E) is co nsidered as a fixed base, free standing, column for purpose of maki ng a calculation of elastic deflection. The elastic deflection line is then plotted as show n and serves as an index for interpreting the load test. Furthermore, on the load deformati on plot, the failure criteri on offset is plotted

PAGE 49

31 parallel to the elastic deformation line (at a distance D/30 inch away) and the point at which the load-deflection curve intersects the failure criterion line is the ultimate capacity, or the failure load. St. Georges Island Bridge Replacement Project0 500 1000 1500 2000 2500 3000 3500 4000 00.40.81.21.622.42.83.23.64 displacement (inch)load (tons) Figure 4-2. Determining capacity of pile, us ing Davisson’s method, for the St. Georges Island Bridge Replacement Project, Load Test-1. 4.2.2 Back Computed Skin and End Bearing Values Once the FDOT ultimate capacity for the load test had been computed, the contribution of skin, and tip towards this load had to be identified. This was achieved by the DeBeer’s method. The method proposed by DeBeer (1967) and DeBeer and Wallays (1972), suggests that in a load distribution curve the capacitie s from skin friction and end bearing can be separated into two separate cu rves of different orders of magnitude as shown in figure 4Elastic Line Failure Line Capacity=1050 Tons D/30

PAGE 50

32 3. We can get back the original load de formation curve by superimposing the two individual curves. Figure 4-3. Separation of load vs. de formation plot into skin and tip. Taking advantage of this fact, if the lo ad deformation curve is plotted on a double logarithmic scale the values fall on two di stinct approximate straight lines, the intersection of which gives th e start of end bearing, as shown in figure 4-4. On this double logarithmic plot, the part of the curve befo re the intersection (fir st half) consists of contribution to the total capacity mainly from skin friction, the part of the curve (second half) after the in tersection corresponds mainly to contribution from end bearing. 1 10 100 1000 0.010.1110 Log (disp)Log (load) Figure 4-4. Separating skin friction and end bearing using DeBeer’s method. Displacement Loa d Actual load deformation plot End Bearing Part SkinFrictionpart FirstHal f Start of End Bearing = 310 Tons Second Half

PAGE 51

33 Table 4-1. Contribution of skin and end bearing in DeBeer's. Contributions First Half Second Half Major Contribution Skin Friction End Bearing Minor Contribution End Bearing Skin Friction For the analysis the load co rresponding to the intersecti on of the two parts of the curve on the double logarithmic scale was taken as capacity from skin friction. One of the most common problems with this method is that in some cases, the tw o straight portions in the graph are not clearly defined. Typical, but hypothetical, load settlement records are shown in Figure 4-5. This provides a very rough estimate of contributions from skin friction and end bearing. In the case of a frictional pile plunging occurs at the failure load a nd a wide range of settlement exists over which essentially the same failure load would be determined if a settlement criterion were used to indicate ultimate load. In the case of a point bearing pile the curve usually exhibits an increase in load with increase in settlement up to extremely high settlements. This is the source of much difficulty in the interpretation of pile load tests. A pile with significant amounts of both point be aring and skin friction will generally plot, bounded by pure point bearing and pure fricti on as limiting conditions (High Capacity Piles, Davisson, M.T). 4.3 Comparison Between Direct and Indirect Method Data from strain gages were available from seven tests (four from St. Georges Island Bridge Replacement Project, and thre e from Woodrow Wilson Bridge Project). Both direct and indirect met hods were used in reducing skin friction, and tip resistance for these tests. The two methods showed good agreement. Table 4-2 shows a comparison between the two methods.

PAGE 52

34 Figure 4-5. Interpretation of Pile load te st. (High Capacity Piles, M.T Davisson) No strain gage data in calc ulating unit end bearing indica tes that the strain gage at the tip failed to produce reliable data during the static loadi ng process, and was not taken into account for calculation as id entified in the load test repo rt (St. Georges Island Test-2, Woodrow Wilson-C, Woodrow Wilson-I).

PAGE 53

35 No data from Davisson’s (unit end bearing) method or DeBeer’s (unit skin friction) method indicates that the load test was not taken to failure so as to interpret the contribution of skin and tip to the total capacity. Table 4-2. Comparison between direct and indirect method. Unit Skin Friction (tsf) Unit End Bearing (tsf) Project Name Strain Gage DeBeer'sStrain Gage Davisson's Method St. Georges Island -1 0.99 1.17 38.4 24.9 St. Georges Island -2 0.28 N.A N.A N.A St. Georges Island -3 0.12 N.A 81.69 N.A St. Georges Island -4 0.85 1.51 48.852 49.822 Woodrow Wilson Bridge-C 0.42 0.53 N.A N.A Woodrow Wilson Bridge-F 0.93 0.85 58.8 51.9 Woodrow Wilson Bridge-I 0.81 N.A N.A N.A

PAGE 54

36 CHAPTER 5 ESTIMATION OF SOIL PLUG Open-ended piles are widely used in offs hore construction. Duri ng the initial stage of installation, soil enters the pile at a rate e qual to the rate of pene tration of the pile. As penetration continues the inne r soil cylinder may develop su fficient frictional resistance to prevent any further soil intrusion, causing the pile to become “plugged”. Although technically the inner soil can be referred to as a “plug” only when it prevents entry of additional soil during penetrati on, the term “soil plug” is co mmonly used in reference to any soil mass inside the pile, regardless of its state during installation (Paikowsky, 1990). The soil plug has to be estimated in or der to determine the end bearing, and the mass of the cylinder pile. The end bearing is required for determining the capacity, and the mass of the pile is required in the drivability analysis. A Finite Element Model of a cylinder p ile penetration was modeled using ADINA (i.e., Automatic Dynamic Incremental Non-Li near Analysis). The properties of this model were based on data from the St. Ge orges Island Bridge Replacement Project. 5.1 Formation of Soil Plug Various researchers have explained the form ation of the column of soil within the pile. The two most popular theories are: 1. Arching phenomenon. 2. Inertial forces on the soil plug.

PAGE 55

37 5.1.1 The Arching Phenomenon During soil plugging within the pile there is an increase in the local resistance in the lower zone of the plug. When this resist ance exceeds the tip bearing capacity, the pile plugs preventing further soil penetration. The increased resistance was explained by using the arching phenomenon (P aikowsky et al., 1990). The arching mechanism is based on the reor ientation of the gra nular soil particles into an arch formation. The arch has a c onvex (upward) curvatur e in the upper zone, attributed to a bulb of reduced stresses during the piles initial penetr ation. The arch has a concave (downward) curvature at the tip of the plug, attributed to a bulb of increased vertical stresses due to pene tration in a plugged or a semi -plugged mode (Figure 5-1). Such an arrangement when subjected to load ing, leads to load transfer into the soil mass. With loads exceeding the arch capacit y, dilation and shear take place along the arch, allowing penetration of additional soil until a new stable arch forms, for which the arch resistance exceeds the upward pushing forc es (tip capacity). This process accounts for zones of varying densities with in the pi le. In all plugged piles the densest soil zone exists a quarter diameter away from the tip. However, in case of unplugged piles the densest zone exists at the tip and the density decreases from the bottom upwards. Pile Section Soil Plug Active convex arch Passive concave arch Figure 5-1. Isobars of the verti cal stress with in the soil pl ug, showing the transition from active to passive arching.

PAGE 56

38 5.1.2 Inertial Forces on the Soil Plug The forces acting on a soil plug during static loading (A) differ from those that act during driving (B), and it is important to distinguish between the two conditions. Figure 5-2. Free body diagram of soil column with in the pile during, A) Static loading, and B) Pile Driving. The free body diagram in Figure 5-2 shows the force system in both cases. The forces acting on the soil plug are: 1. Frictional force: The soil plug feels this force, in the downwar d direction, on the pile soil interface. Its magn itude (Fs) is equal to th e product of the plug surface area, times the unit skin friction value at the interface. As this study was carried out to see the effects of soil plug diameter, and g-forces on the soil plug height, the interface frictional coefficient was chosen to be a constant value for the parametric study (Based on design curves for cyli nder pile, discussed in chapter-6). 2. Weight of the soil plug: The weight (W ) of the soil plug is the product of the volume of the soil plug, times the total unit weight of soil. This force acts in the downward direction. W I Qt Fs Fs W (A) Fs Fs W Qt (B) I Lp

PAGE 57

39 3. Tip Resistance: The tip resistance acting on the soil plug is equal to the product of the plug cross sectional area, times the unit tip resistance. This force acts in the upward direction trying to un-stabilize the plug. 4. Inertia Force: The inertial force is equa l to the product of the plug mass, and the plug acceleration, and represents the resistan ce of the plug weight to the downward acceleration imparted by the hammer to the pile-plug system. The inertial force acts in the upward direction, trying to oppos e the motion, and creating a resultant upward force. If the inertial effects are la rge enough, the pile will continue to core. The inertial force acts only dur ing the driving process. The assumptions made in these calculations are: 1. The g-forces on the soil plug is constant for the full length, and its value equal to the average g-forces on the embedded portion of the pile. 2. The damping forces were ignored for th e calculation purpose as discussed in section 5.3.4. 5.1.2.1 During static loading The forces acting during static loading are as follows: Qt W Fs Eq.5-1 qt D Lp D Lp Dfs ) 4 ( ) 4 ( ) (2 2 Eq.5-2 qtD D fs Lp25 0 ) 25 0 { Eq.5-3 ) 25 0 ( 25 0 D fs qtD Lp Eq.5-4 Lp = Length of the plug (ft). D = Diameter of the plug/ inner diameter of the pile (inch). = Total unit weight of soil (pcf). fs = Unit skin friction between the plug and pile (tsf). Fs = Total skin frictional force (Tons). qt = unit end bearing at pile toe (tsf).

PAGE 58

40 Qt = Total tip resistance on the soil plug (Tons). W = weight of the soil plug (Tons). 5.1.2.2 During driving The forces acting during driving are as follows: I Qt W Fs Eq.5-5 g g ap Lp D qt D Lp D Lp Dfs* ) 4 ( ) 4 ( ) 4 ( ) (2 2 2 Eq.5-6 qtD ap D D fs Lp25 0 ) 25 0 25 0 { Eq.5-7 )) 1 ( 25 0 ( 25 0 ap D fs qtD Lp Eq.5-8 ap = average plug acceleration in g’s. Equation 5-8, explains plug heights increas e with increase in soil plug diameter (accountable to inertia of the soil plug). A simple case study performed by Stevens showed that if the average plug acceleration is greater than 22g, the pile will not plug during driving. Average peak accelerations ranging from 169 to 215g have been measured during the driving of large di ameter offshore piles (Stevens, 1988). Equation 5-4, accounts for plugging once the pile is subs equently loaded statically, as the plug will have considerab le resistance to movement, since the shaft resistance greatly exceeds the end bearing that can be mobilized by the soil plug. 5.1.3 Parametric Study – Effects of Diameter, and G-Forces Figure 5-3, shows a screen shot of the mathcad file developed based on equation 58 to study the effects of pile diameter, and acceleration due to grav ity of the soil plug on plug heights.

PAGE 59

41 The input parameters are the outer diameter of the pile, shell thickness (to calculate the diameter of the soil plug), soil type (same classification as SPT2000), SPT N values for unit skin friction, and un it end bearing calculations, a nd submerged unit weight of soil. Figure 5-3. Screen shot of the MathCAD file showing pl ug height, upward force, and downward force calculations. Parametric study was carried out on piles of six different diamet ers (54”, 38”, 24”, 20”, 16”, and 12”), and the g-forces varied fr om 0-g (static loading case) to 45-g. Table 5-1 tabulates the various pa rameters and their values.

PAGE 60

42 Table 5-1. Fixed parameters in study, and values. Parameter Value Soil Type Silt Pile Material Concrete SPT N Value for Skin 25-blows SPT N Value for Tip 30-blows Pile Length 80-ft Plug Height Curve 0 20 40 60 80 100 120 010203040 average g-force on soil plugHeight of Plug (ft) ID=54" ID=38" ID=24" ID=20" ID=16" ID=12" Figure 5-4. Variation of plug height with soil plug diameter and g-forces. Figure 5-4, plots the plug he ights for soil diameters (inner diameter of the pile) of 54-inch, 38-inch, 24-inch, 20-inch, 16-inch, and 12-inch using equations 5-8 (MathCAD output). Pile Len g th=80-ft Static loadin g case g =0 ( Y-axis ) Critical g-force for 54” Pile

PAGE 61

43 The intersection of the soil plug curve with the 80-ft lin e (pile length) corresponds to the “critical g-force value”. At g-force valu es above the critical g-force value there will be no plug formation, at g-force values below the critical g-force value a plug will form, the length of this plug will be directly proportional to the g-force that the plug experiences during the driving process. Smalle r diameter piles have smaller plug heights as compared to large diameter piles (i.e., sm aller diameter piles plug faster than a large diameter pile). Table 5-2. Critical g-force values with diameter. Soil Plug Diameter Critical g-force Value 54-inch 15-g 38-inch 24-g 24-inch 42-g 20-inch <45-g 16-inch <45-g 12-inch <45-g From this study it is clear that the plug hei ght is very sensitive to the volume of soil within the pile (i.e., square of the inner di ameter), and acceleration due to gravity of the soil plug. This would result in large diameter piles cutting through soil (unplugged) rather than forming a plug. Change in soil type (sand, clay, and silt) was not an impacting factor in this study (soil type varied for same blow counts giving diffe rent fs values). 5.2 ADINA Theory and Modeling The pile model was completely described, including the geometry of the model, material properties, boundary conditions a nd loads using the pr e-processor ADINA-IN and analyzed using the structural analysis program ADINA of the AUI System (i.e., ADINA User Interface).

PAGE 62

44 5.2.1 General Overview of the Pile Model The pile was modeled as a two-dimens ional, nine node, axisymmetric solid element. The axisymmetric element provides for the stiffness of one radian of the structure. ADINA models the elements as isoparametr ic displacement-based finite elements. The principal idea of using an isoparametric finite element formulation was to achieve the relationship between the element displacement at any point, and the element nodal point displacement directly through the use of interpolat ion function (also called the shape function). A Local Cartesian coordinate system wa s used in defining the model points. The pile had two degrees of freedom, the translat ion in the yz-plane. The points were then bound together using a vertex surface to define the pile. A vertex surface is one whose geometry is defined by points (unlike a patch surface whose boundary is defined by lines). The sides of the pile coming in contact with the soil were defined as fluid-structure boundaries (section 5.3.3). Z xy = 0 xz = 0 X Y xx = u/y Figure 5-5. Isoparametric Nine Node Axisymmetric Element

PAGE 63

45 5.2.2 Material Model of the Pile The elastic isotropic material model was used to describe the pile. The two material constants used to define the constitutive relation were E (i.e., Young’s Modulus), and (i.e., Poisson’s Ratio). 5.2.3 Properties of the Pile The model pile was assigned values ba sed on data from the St. Georges Island project. The average penetration of the pile taking into consideration the time intervals between blows, was taken to be roughly 0.4i nch/sec, which is comparable to the soil penetration rate recommended for deep, quasi-s tatic penetration tests of soil (0.4-0.8 inch/sec, ASTM 1979). Further, a range of valu es was chosen for the pile property so as to carry out a parametric study. This study wa s used to find out the factors impacting the formation of a plug within the pile and thei r extents. Table 5-3 summarizes the properties of the pile and the variations. Table 5-3. Pile Properties and its variations Pile Property Actual Model Parametric study Model Pile Length 80 ft 80 ft Outer Diameter 54 inch 36 inch60 inch Shell Thickness 8 inch 10 inch6 inch Young’s Modulus 6300 ksi 6300 ksi Poisson’s Ratio 0.15 0.15 Unit Weight 150pcf 150pcf Rate of Penetration 0.5 inch/s ec 0.3 inch/sec0.5inch/sec 5.2.4 Pile Formulation The pile was formulated using the Lagr angian coordinate system. In this formulation, the mesh moves with the materi al particles. Hence, the same material particle was always at the same element mesh point. In order to recreate the pile penetration process, keeping in mind the modeli ng constraints, the top end of the pile was

PAGE 64

46 held fixed and the soil was pushed from th e bottom boundary with traction of 100psf, so as to give the pile a relative downwar d movement of .5inch/sec (section 5.2.3). Figure 5-6. ADINA pile input, thic k lines indicating contact surface 5.3 ADINA-F Theory and Modeling The soil properties, boundary conditions, a nd pile loading were modeled using the ADINA-F (i.e., ADINA-Fluid) feature of the AUI system. The soil boundary was chosen larger than 7.5 times the pile diameter so as to avoid boundary eff ects as suggested by Vipulanandan et al. (1989). 5.3.1 General Overview of the Soil Model The soil was assumed to be an inviscid axisymmetric two-dimensional steady state flow problem, where the soil particle s move along streamlines around the pile as modeled by Azzouz et al. (1989). A total of five vertex surfaces were used to define the soil mass.

PAGE 65

47 5.3.2 Material Model of the Soil “Constant property” material model was us ed to define the soil mass. Variations were later made in the propert ies of the soil so as to carry out a parametric study. The loose and dense sand behavior of soil was modeled using the compressible and incompressible flow types. 561 nodes were us ed in defining the entire soil mass. 5.3.3 Boundary Condition A no slip boundary condition was applied along the pile soil interface so as to introduce shearing action between the pile and soil (surface 1, 2, and 3). A slip surface was introduced on boundary surfaces that defined the soil mass (4 and 5). 1 3 2 4 5 Figure 5-7. Figure showing the slip and no slip surfaces along the various boundaries 5.3.4 Properties of the Soil Model Chow suggested that, with a proper repres entation of soil hysteresis using very simple parameters like Young’s modulus (E), Poisson’s Ration ( ), Shear Strength (Cu) and by incorporating the soils mass density ( ), typical pile drivi ng responses could be

PAGE 66

48 recovered without resorting to any other soil damping and sti ffness parameters such as J and Qu in the original E.A.L Smith mode l. (I.M Smith and S.M Wilson, 1981). Table 5-4 summarizes the prope rties of the soil and the ra nge of values chosen for carrying out a parametric study. Table 5-4. Soil Properties and its Variation Soil Property Actual Model Parametric Model Unit Weight 100pcf 80pcf-120pcf Friction Angle/ Dynamic Shear Strength 28degree/ 500pa-sec 28degree/ 500pa-sec – 35degrees/ 2000pa-sec 5.3.5 Soil Formulation The soil particles can under go very large displacements and were formulated using the Eulerian coordinate system. Figure 5-8. Showing an ADINA-F soil mesh In the Eulerian formulation, the mesh poi nts are stationary and the soil particles move through the finite element mesh in the prescribed direction. In this formulation, attention is focused on the moti on of the material through a st ationary control volume and

PAGE 67

49 that we use this volume to measure the equilibrium and mass continuity of the soil particles. 5.4 ADINA-FSI Theory and Modeling The ADINA pile model and the ADINA-F soil model were merged together using the feature of ADINA-FSI (i.e., Fluid Structure Interaction). In FSI, the fluid forces (soil) are applied onto the solid (pile), and the so lid deformation changes the fluid (soil) domain. The pile was based on the Lagrangi an coordinate system, and the soil was modeled using the Eulerian coordinate sy stem. For the FSI model, the coupling was brought about based on the arbitrary-Lagra ngian-Eulerian (ALE) coordinate system. When any part of the comput ational domain is deformable, the Eulerian description of soil (fluid) flow is no longe r applicable and the Lagrangian description must be used. Anywhere else in the soil (flu id) domain, the fluid flow can be described in an arbitrary coordinate system as long as it meets th e coordinate requirements along the boundaries. Such a description is called an arbitraryLagrangian-Eulerian formulation and was used in the FSI modeling. In an arbitrary-Lagra ngian-Eulerian formulation, the mesh points move but not necessarily with the material particles. In fact, the mesh movement corresponds to the nature of the movement and is imposed by the solution algorithm. While the finite element mesh spans the complete analysis domain throughout the solution and its boundaries move with the m ovements of free surfaces and structural boundaries, the soil particles move relative to the mesh points. The approach allows the modeling of interaction between soil and pile.

PAGE 68

50 A) B) Fluid Structure Interface Axisymmetric pile section Soil Soil Figure 5-9. Contact surface geometry: A) Ax isymmetric section of a cylinder pile showing the contact surfaces, B) se ction showing interface elements. 5.5 ADINA Plot The results of the ADINA-FSI were then viewed using the post processor ADINAPLOT. Figure 5-10 shows the plot files fo r both pile (ADINA) and soil (ADINA-F). Figure 5-10. ADINA Plots: A) Plot of the pile as generated by ADINA, B) Plot of the soil mass as generated by ADINA-F, showing th e cavity where the pile is placed in the ADINA-FSI model. A B Pile Soil Plug Cavity for Pile

PAGE 69

51 Information such as nodal velocities at the ten nodes on the plug surface and stresses with in the pile was then monitored. Figure 5-11. Flow chart indi cating the various steps in the analysis of the plug 5.6 Factors Affecting the Soil Plug In order to estimate the factors impacting the length of the soil plug the following soil and pile parameters were varied 1. Shell thickness. 2. Outer diameter of Pile. 3. Rate of penetration of the pile. 4. State of Soil (loose or dense). 5. Dynamic shear strength of soil. 6. Unit weight of soil. 5.6.1 Assumptions in Estimating the Soil Plug The assumptions for estimating the height of the soil plug were based on information from the St. Georges Island Bridge Replacement Project. In the St. Georges Island Bridge Replacemen t project, the soil within the pile did not form a plug. Identical results were obtained from the ADINA-F model using properties listed in tabl e 5-2 and table 5-3. ADINA-Fluids (Soil formulation) ADINA-IN ( Prep rocessor ) ADINA ( Pile formulation ) ADINA-FSI (Merging the soil and pile models) ADINA-PLOT ( Viewin g and anal y zin g the out p ut )

PAGE 70

52 The soil within the pile rose to the full pi le length of 80 feet (100% Plug height). At 100% plug height, the soil within the p ile reached a terminal velocity, which was about 5 times less than the initial velocity within the pile. Also, at this stage the maximum velocity in the pile soil system was about 70 times the velocity of the soil plug. Figure 5-12. Velocity profile with in the finite element model: A) Velocity profile with in the finite element model, pile stationary and soil moving, B) Velocity profile with in the model, pile moving, and soil stationary. In Figure 5-12, the length of the arrows is proportional to th e magnitude of the velocity. The thick arrow represents the maximum velocity zone, Vmax. Figure 5-12 a, shows the velo cities in the system during the plugged stage, in the actual finite element model. The pile is statio nary (has zero velocity). The lowest soil particle velocity is that of the soil plug, which is zero, or in case of partially plugged it is a small upward one, Vp. The highest velocity is that of the soil particles furthest from the pile surface (boundaries are slip surfaces), Vmax. The finite element model shown in Figure 5-12 a, is translated into an actual pile penetration process by subtrac ting the entire system velocity by a downward Vmax, as A B

PAGE 71

53 shown in Figure 5-12 b. With the result, the pile moves downwards with a velocity of Vmax. The plug moves downwards w ith a velocity of (Vmax-Vp) in case of partially plugged, or Vmax in case of fully plugged. Velocity Ratio (VR) = Velocity of the plug / Velocity of the Pile max ) max ( V Vp V VR Eq.5-9 Dividing, equation 5-3 by Vp we get, Vp V Vp V VR max 1 max Eq.5-10 From, St. Georges Island Project, 70 max Vp V Substituting in equation 5-4, VR = 0.9857 0 < VR < 1 (VR = 1, Pile is plugged, VR = 0, Pile is unplugged). A Velocity Ratio of 0.98 was the highest that was obtained using ADINA, and for all-purposes this was taken as the stage of so il plug formation. At this stage the soil and the plug are moving with the same velo city (relative velocity of zero). Figure 5-13, shows the variation of veloci ty ratio with increase in % plug height. 100 % PileLength PlugLength height Plug Eq.5-11 The % plug length (%PL) refers to the lengt h of the plug relative to the length of the pile and was a helpful modeling concept. By using the %PL, the tip elevation of the pile could be kept constant for various plug lengths, and the movement of the soil particles with in the pile could be monitored.

PAGE 72

54 Velocity Ratio Vs % Plug Height 0 20 40 60 80 100 120 0.940.950.960. 970.980.991 Velocity Ratio% Plug Height Figure 5-13. Plot showing varia tion in velocity with in the pile with change in plug height. 5.6.2 Unplugged Soil Velocity Profile Two stages, once during un-plugged condi tion, and the other during plugged condition, were chosen to show the difference in the velocity profile with in the pile. The plots were made usi ng ADINA-Plot, and a 32-color scheme option. Figure 5-14 shows an axisymmetric pile section during the unplugge d stage (plug height is 20% of the pile length). The soil around the pile wall best indicates the velocity of the pile. At this stage, when the pile is moving down with a velocity indicated by the blue color profile (top end of the color scheme) the so il with in the pile is moving with a much smaller velocity (lower end of the spectrum), this means that there exists a large relative velocity between the soil plug and the pile indicating that the pile has not plugged.

PAGE 73

55 Figure 5-14. Velocity profile with in cylinder pileunplugged condition 5.6.3 Plugged Soil Velocity Profile Figure 5-15, shows an axisymmetric pile section during the plugged stage (plug height is 88% of the pile height). At this stage the terminal veloci ties have been reached. A uniform velocity has been atta ined with in the pile whose value is almost equal to the velocity of the pile. At this stage, the pile and the soil with in, have almost zero relative velocity indicating formation of soil pl ug (pile and soil plug moving together).

PAGE 74

56 Figure 5-15. Velocity profile with in cylinder pileplugged condition 5.6.4 Variation in Shell Thickness The geometry of the Pile play s an important part in the rise of soil with in the pile. A parametric study was done with shell thickness varied from 10” to 6”, with constant outer diameter, 54”. The results observed were in accordance with Ki ndel’s theory that, plug movements tend to stabilize due to decr ease in the inside volume resulting from an increase in the pile wall th ickness (Paikowsky et al., 1990). Th is result also supports the theory that pipe piles have a higher chance of plugging as compared to large diameter cylinder piles, owing to a smaller inertial force (lesser soil plug mass) as discussed in

PAGE 75

57 section 5.1.1. In Figure 5-16 the points mark ed X indicates the pile used at the St. Georges Island Bridge Replacement Project. Loose sands were found to have slightly larger plug heights as compared to dense sands. Variation in Shell Thickness at constant diameter = 54"0 20 40 60 80 100 120 10* 86 Thickness (inch)% Plug Height Loose Sand Dense Sand Indicates standard pile used for comparison. Outer Diameter = 54”, Shell Thickness = 8”, Unit Weight = 100pcf, Dynamic Shear Strength/Fr iction angle=1000pa-sec/30deg, Rate of Penetration= 0.5inch/sec. Figure 5-16. Plot showing variation of sh ell thickness with height of soil plug 5.6.5 Variation in the Outer Diameter of the Pile To study the variation in diam eter, the geometry of the p ile was varied, but the ratio of diameter to the shell thickness was kept c onstant, ratio of 6. A comparison between the two piles with the same shell thickness a nd different diameters (8”-54” and 8”-48”) indicates that the pile with the smaller diameter plugs faster. This result was in agreement with tests conducted by Kishida (1967).

PAGE 76

58 V ariation in shell thickness and diameter at constant ratio = 60 10 20 30 40 50 60 70 80 90 10"-60"* 8"-54" 8"-48"6"-36" shell thickness"-Diameter"%Plug Height Loose Sand Dense Sand Indicates standard pile used for comparison. Outer Diameter = 54”, Shell Thickness = 8”, Unit Weight = 100pcf, Dynamic Shear Strength/Fr iction angle=1000pa-sec/30deg, Rate of Penetration= 0.5inch/sec. Figure 5-17. Plot showing vari ation in the soil plug with change in outer diameter Table 5-5. Values used for pile outer diameter parametric study Outer Diameter Shell Thickness Ratio 60 10 6 48 8 6 36 6 6 5.6.6 Variation in the Rate of Penetration of the Pile The rate at which the pile is driven into the soil was found to have a considerable impact on the height of soil plug in the pile. Parametric study was carried out with rates varying from 0.3inch/sec to 0.5inch/sec. The following results were obtained.

PAGE 77

59 Variation in Rate of Penetration60 65 70 75 80 85 90 .5inch/sec.4inch/sec.3inch/sec Velocity of Pile% Plug Height Loose Sand Dense Sand Indicates standard pile used for comparison. Outer Diameter = 54”, Shell Thickness = 8”, Unit Weight = 100pcf, Dynamic Shear Strength/Fr iction angle=1000pa-sec/30deg, Rate of Penetration= 0.5inch/sec. Figure 5-18. Variation in Rate of Penetration 5.6.7 Variation in Shear Strength of Soil Dynamic Shear Strength values of sta ndard sand were obtained and compared with the friction angle value ( These values were varied fo r the purpose of parametric study. The friction angle was found to be str ong influencing factor. The plug heights went up 40% when the friction angle was redu ced from 35 degrees to 27.5 degrees.

PAGE 78

60 Variation in Dynamic Shear Strength0 20 40 60 80 100 120 X: 500 pa-sec or 27.5degree 1000 pa-sec or 30degree 1500 pa-sec or 32.5degree 2000 pa-sec or 35degree Dynamic Shear Strength or Friction Angle% Plug Height Loose Sand Dense Sand Indicates standard pile used for comparison. Outer Diameter = 54”, Shell Thickness = 8”, Unit Weight = 100pcf, Dynamic Shear Strength/Fric tion angle=1000pa-sec/30deg, Rate of Penetration= 0.5inch/sec. Figure 5-19. Variation in Friction angle or Dynamic shear Strength 5.6.8 Variation in Unit Weight of Soil The density of soil was varied from 80pc f to 120pcf. The following results were obtained. These results contradicted the fact that dense sands have a smaller plug height as compared to loose sands.

PAGE 79

61 Variation in Unit Weight72 74 76 78 80 82 84 86 88 90 80 pcf* 100 pcf120 pcf Unit Weight (pcf)%Plug Height Loose Sand Dense Sand Indicates standard pile used for comparison. Outer Diameter = 54”, Shell Thickness = 8”, Unit Weight = 100pcf, Dynamic Shear Strength/Fr iction angle=1000pa-sec/30deg, Rate of Penetration= 0.5inch/sec. Figure 5-20. Variation in Unit Weight of Soil

PAGE 80

62 CHAPTER 6 SKIN FRICTION AND END BEARING CURVES 6.1 Unit Skin Friction and Unit End Bearing Curves The load test data was reduced into unit skin friction and end bearing (as discussed in Chapter-4), and plotted as a scatter pl ot against uncorrected blow counts (N), corresponding to the soil type and pile mate rial. Best-fit curves were drawn through the scatters, and the curve co rresponding to the best R2 (Regression coefficients) value was chosen. Five curves were formulated corresponding to skin friction: 1. Concrete piles in sands. 2. Steel piles in sands. 3. Concrete piles in clays. 4. Steel piles in clays. 5. Concrete piles in silts. Three curves were formulated corresponding to end bearing: 1. In sands. 2. In clays. 3. In silts.

PAGE 81

63 fs = 0.3084Ln(N) 0.4599 R2 = 0.83880 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 051015202530354045505560 SPT N ValuesUnit Skin Friction (TSF Figure 6-1. Skin friction (tsf) Vs N (uncorrected) for concrete piles in sand. fs = 0.2028Ln(N) 0.2646 R2 = 0.85040 0.1 0.2 0.3 0.4 0.5 0.6 0.7 05101520253035404550556065 SPT N ValueUnit Skin Friction (TSF) Suggested Limit Figure 6-2. Skin friction (tsf) Vs N (uncorrected) for steel piles in sand. Modified trend line. Suggested Limit.

PAGE 82

64 fs = 0.5083Ln(N) 0.634 R2 = 0.94480 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 05101520253035404550 SPT N ValueUnit Skin Friction (T S Figure 6-3. Skin friction (tsf) Vs N (uncorrected) for concrete piles in clay. fs = 0.4236Ln(N) 0.5404 R2 = 0.89650 0.2 0.4 0.6 0.8 1 1.2 0510152025303540455055 SPT N ValueUnit Skin Friction (T S Figure 6-4. Skin friction (tsf) Vs N (uncorrected) for steel piles in clay. Modified trend line. Suggested Limit.

PAGE 83

65 fs = 0.3265Ln(N) 0.2721 R2 = 0.89940 0.2 0.4 0.6 0.8 1 1.2 1.4 05101520253035404550556065 SPT N ValueUnit Skin Friction (TSF) Figure 6-5. Skin friction (tsf) Vs N (uncorrected) for concrete piles in silts. qt = 0.5676x R2 = 0.88350 10 20 30 40 50 60 0510152025303540455055606570758085909510 0 10 5 SPT N Valueqt (TSF) suggested limit Figure 6-6. End bearing (tsf) Vs N (uncorrected) in Sands. Modified trend line. Concrete Steel

PAGE 84

66 qt = 0.2276x R2 = 0.96160 1 2 3 4 5 05101520 SPT N ValueUnit End Bearing (TSF) Figure 6-7. End bearing (tsf) Vs N (uncorrected) in Clays. qt = 0.4101x R2 = 0.88670 2 4 6 8 10 12 14 05101520253035 SPT N ValueUnit Skin Friction (TSF) Figure 6-8. End bearing (tsf) Vs N (uncorrected) for silts. Modified trend line. Con crete Steel

PAGE 85

67 6.2 Comparison of Skin Friction and End Bearing with SPT2000 In order to compare the cy linder pile design with the existing design used in the SPT2000 program, six graphs were plotted na mely, unit skin friction vs. SPT N values, and unit end bearing vs. SPT N values for, clays, silts, and sands. Each curve consists of a set of four curves, namely: 1. SPT2000 for small piles. 2. SPT2000 for steel pipe piles. 3. Large diameter cylinder pile, concrete. 4. Large diameter cylinder pile, steel.

PAGE 86

68 Unit Skin Friction in Clays 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 010203040506070 SPT N ValuesUnit Skin Friction (tsf) SPT97, Concrete Piles SPT97, Steel Piles Large Diameter Pile, concrete Large Diameter Pile, Steel No Data zone Figure 6-9. Comparison of various designs used for computing unit skin friction in clays.

PAGE 87

69 Unit Skin Friction in Silts 0 0.2 0.4 0.6 0.8 1 1.2 1.4 010203040506070 SPT N ValuesUnit Skin Friction (tsf) SPT97, Concrete Piles SPT97,Steel Piles Large Diameter Piles, Concrete No Data zone Figure 6-10. Comparison of vari ous designs used for computi ng unit skin friction in silts.

PAGE 88

70 Unit Skin Friction in Sands0 0.2 0.4 0.6 0.8 1 1.2 010203040506070 SPT N ValuesUnit Skin Friction (tsf) SPT97, Concrete Piles SPT97, Steel Pile Large Diameter Pile, Concrete Large Diameter Pile, Steel No Data zone Figure 6-11. Comparison of vari ous designs used for computi ng unit skin friction in sands.

PAGE 89

71 End Bearing in Clays 0 2 4 6 8 10 12 14 16 010203040506070 SPT N ValuesUnit End Bearing (TSF) SPT97, Concrete Piles SPT97, Steel Piles Large Diameter Piles (steel/concrete) No Data zone Figure 6-12. Comparison of vari ous designs used for computi ng unit end bearing in clays.

PAGE 90

72 END BEARING IN SILTS 0 5 10 15 20 25 30 35 010203040506070 SPT N ValuesUnit End Bearing (TSF) SPT97, Concrete Piles SPT97, Steel Piles Large Diameter Pile (steel/concrete) No Data zone Figure 6-13. Comparison of vari ous designs used for computi ng unit end bearing in silts.

PAGE 91

73 End Bearing in Sands0 10 20 30 40 50 60 70 010203040506070SPT N ValuesUnit End Bearing (TSF) SPT97, Concrete Piles SPT97, Steel Piles Large Diameter Pile (steel/concrete) No Data zone Figure 6-14. Comparison of vari ous designs used for computi ng unit end bearing in sands.

PAGE 92

74 Unit Skin Friction Curves0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 010203040506070SPT N ValuesUnit Skin Friction (TSF) Concrete, Clay Steel, Clay Concrete, Silts Concrete, Sands Steel, Sands Figure 6-15. Comparison of unit skin friction vs. SPT N values, for various soil types, and pile materials, in case of cylinder piles.

PAGE 93

75 Unit End Bearing Curves for Cylinder Piles 0 5 10 15 20 25 30 35 010203040506070 SPT N ValuesUnit Skin Friction (tsf) Clays Silts Sands Figure 6-16. Comparison of unit end b earing vs. SPT N values, for various soils, in case of cylinder piles.

PAGE 94

76 CHAPTER 7 LOAD AND RESISTANCE FATOR DESIGN (LRFD) For many years, allowable stress design (ASD ) was used for the design of bridges, building and other structures. In the 1970’s, the American A ssociation of State Highway and Transportation Officials (AASHTO) intr oduced a new design procedure for bridge superstructures. The design procedure was known as load factor design (LFD). It revolutionized the design of br idge superstructure by allowing the structural engineer to set different factors for differe nt types of loads on the bridge But, when the structural engineer designed the superstruc ture, he/she had to keep track of two different sets of loads. One set for the superstructure, which required factored loads, and one set for the foundation design, which was still using ASD method. In the 1980’s, resistance factors were introduced into LFD. This created a new design method known as load and resistance factor design (LRFD). An important goal of driven pile desi gn is to prevent a limit state from being reached. This goal is implied by both th e traditional "allowabl e stress design"--ASD method (by means of the safety factor Fs) and the "load and resi stance factor design"-LRFD method (by means of the load factors i and the resistance factor ). However, other goals that must be considered and ba lanced in the overall design are function, appearance, and economy. The LRFD, which is presented in section 7-2, has more advantages over the ASD, which is presented in section 7-1, in achieving these goals.

PAGE 95

77 7.1 Allowable Stress Design Before the introduction of LRFD, ASD wa s used for all designs. ASD works by reducing the calculated or estimated resistances by a global factor of safety, resulting in a maximum design load. The estimated loads (or stresses) Q i are restricted as shown bellow: Fs Rn Q I Eq.7-1 Where: Rn = Nominal resistance, Fs = Factor of safety--usually from 2.0 to 4.0, and Qi = Load effect (dead, live and environmental loads). For pile foundations, the e quation can be rewritten as: Rn / Fs = (Rs + Rp) / Fs QD + QL Eq.7-2 Where: QD = Dead load, QL = Live load, Rs = Side resistance, and Rp = Tip resistance. 7.2 Load Resistance Factor Design The LRFD specifications as a pproved by AASHTO (A ASHTO, 1996/2000) recommend the use of load fact ors to account for uncertainty in the loads, and resistance factors for the uncertainty in the material resi stances. This safety criterion can be written as: Rn i Qi Eq.7-3 Where: Rn = Nominal resistance,

PAGE 96

78 = Load modifier to account for eff ects of ductility, redundancy and operational importance. The value of usually ranges from 0.95 to 1.00. In this thesis, = 1.00 is used. Qi = Load effect. i = Load factor. Based on current AASHTO recommendation, the following factors are used: D = 1.25 for dead load, L = 1.75 for live load, = Resistance factor--Usually ranges from 0.3 to 0.8. For driven piles, we have Rn 1.25 QD + 1.75 QL Eq.7-4 If different resistance factors are used for tip and side resistance, then sRs + pRp 1.25 QD + 1.75 QL Eq.7-5 Where: Rs = Side resistance, Rp = Tip resistance, and s; p= Resistance factors for side and tip resistance, respectively. The LRFD approach has the following advantages: It accounts for variability in both resistan ce and load. (In ASD, no consideration is given to the fact that different loads ha ve different levels of uncertainty). For example, the dead load can be estimated with a high degree of accuracy; therefore, it has a lower factor (1.25) in LRFD. It achieves relatively uniform levels of safety based on the strength of soil and rock for different limit states and foundation types.

PAGE 97

79 It provides more consistent levels of safety in the superstructure and substructure as both are designed using the same loads for known probabilities of failure. In ASD, selection of a factor of safety is subj ective, and does not provide a measure of reliability in terms of probability of failure. Using load and resistance factors provided in the code, no comp lex probability and statistical analysis is required. The limitations of the LRFD approach include: Implementation requires a change in desi gn procedures for engineers accustomed to ASD. Resistance factors vary with desi gn methods and are not constant. The most rigorous method for developing a nd adjusting resistance factors to meet individual situations requires the availab ility of statistical data and probabilistic design algorithms. 7.3 Calibration of Resistance factor for LRFD Calibration of resistance factors is defined as the process of finding the values to achieve a required target probability of surviv al. There are three approaches that have traditionally been used in the LRFD calibration. 7.3.1 Engineering Judgment The factor is assigned empirically by e ngineering judgment, and it is to be adjusted by the past and future performan ce of foundations designe d using that factor. 7.3.2 Fitting ASD to LRFD The resistance factor is fitted through the factor of safety Fs and other load parameters by equating equati on 7-2 and equation 7-4: 1L D s L L D DQ Q F Q Q Eq.7-6

PAGE 98

80 If D = 1.25 and L = 1.75 as recommended by AASHTO and if QD/QL is from 1.0 to 4.0 then = sF 1.35 to 1.50 Eq.7-7 Equation 7-7 is the basic calibration equa tion for calibrating the LRFD resistance factor by fitting with ASD. 7.3.3 Reliability Calibration There are three levels of probabilistic design (Withiam et al., 1997). The fully probabilistic method (i.e.,, leve l III) is the most complex and requires knowledge of the probability distributions of each random variab le and correlations between the variables. The level I method is referred to as the mean value first order second moment (MV FOSM) method. The level II method, which is recomm ended by AASHTO and FHWA, is referred to as the advanced first order second mo ment method (A FOSM). The equations presented in this section are based on level II method, adapted from the FHWA workbook (Withiam et al., 1997). 7.3.3.1 Resistance bias factor The resistance bias factor is defined as: n m RiR R Eq.7-8 Where: Rm = Measured Resistance, Rn = Predicted (Nominal) Resistance The mean, standard deviation and coefficien t of variation of th e set of bias data Ri are

PAGE 99

81 Mean: NRi R Eq.7-9 Standard Deviation: 12 NR Ri R Eq.7-10 Coefficient of Variation: R R RCOV Eq.7-11 The mean of the bias factor represents a trend between what is predicted and what is measured. 7.3.3.2 Reliability index Figure 7-1 presents the graph of the probability distribution function of ) ln( Q R g Eq.7-12 R = pile capacity, which is ( Rn), Q = load effect, which is ( QD QD + QL QL). When the pile capacity R is smaller than th e load effect Q, then g < 0, represented by the shaded region in figure 7-1. This shaded zone is also referred to as the probability of failure, pf In pile foundation design, a range from 0.1% to 10.0% is used. This range is high because piles are usually used in groups failure of one pile does not necessarily imply that the pile group will fail. The reliability index is defined as the ratio between the lognormal mean, g, and the lognormal standard deviation, g,. gg or g= g Eq.7-13

PAGE 100

82 Figure 7-1. Failure region and the reliability In Figure 7-1, if is higher, then g is higher, the graph is stretched further to the right and the failure region, pf, will be smaller. Rosenblueth and Esteva, 1972 (cited in Withiam et al., 1997) developed the following simple equation relating pf with : pf = 460 e-4.3 (2 < < 6) Eq.7-14 For civil engineering project, usually ranges from 2.0 to 4.0. However, due to the redundancy of pile groups, AASHT O and FHWA recommend using from 2.0 to 2.5 for pile foundations (cited in Withiam et al., 1997), and it is called the targ et reliability index T. Table 7-1. Relationship between probability of failure and reliabili ty index for lognormal distribution (Rosenblue th and Esteva, 1972). Reliability Index, Probability of failure, Pf 2.25 .29E-1 2.5 .99E-2 3.0 1.15E-3 3.5 1.34E-4 4.0 1.56E-5 4.5 1.82E-6 Reliability Index, Probability of failure, Pf 1E-1 1.96 1E-2 2.5 1E-3 3.03 1E-4 3.57 1E-5 4.1 1E-6 4.64

PAGE 101

83 7.3.3.3 Resistance factor According to AASHTO (cited in Withia m et al., 1997), the lognormal distribution function should be used for resistance bias f actors because it represents the distribution of the resistance data. )] 1 )( 1 ln[( exp ) ( 1 1 ) (2 2 2 2 2 2 QL QD R T QL L D QD R QL QD L L D D RCOV COV COV Q Q COV COV COV Q Q Eq.7-15 Where: = Resistance factor, D = Dead load factor (1.25), L = Live load factor (1.75), R = Resistance bias factor, COVR = Resistance coefficient of variation, QD, QL = Dead load and live load bias factors, COVQD, COVQL = Dead load and live load coefficients of variation, T = Target reliability index (2.0 to 2.5), QD/QL = Dead to live load ratio. Hansell and Viest, 1971 (cited in With iam et al., 1997) developed the following empirical equation for the QD/QL ratio: QD/QL = (1+ IM) 0.0132 L Eq.7-16 where: IM = Dynamic load allowance factor (usually equal to 0.33), L = Span length (feet). QD/QL usually ranges from 1.0 to 3.0 (corresponding to L = 57-170 ft).

PAGE 102

84 7.4 Capacity Prediction Two different approaches were used in pred icting the capacity of the pile. Capacity from: 1. (Skin friction over the outside area ) + (end bearing over the ring area) 2. (Skin friction over the outsid e area) + (end bearing over th e entire cross-sectional area) The first approach, in which the capacity from end bearing is calculated over only the ring area was found to be more conserva tive, as opposed to calculating the end bearing over the entire crosssectional area. The values of mean bias, coefficient of variation, and the LRFDfactor were compared for the two approaches. The first approach of using the end bear ing capacity over the ring area was found to be more conservative (higher factor), and defined as means of predicting capacity. Figure 7-2, shows the variation of -factor with variation in load factor, for different reliability index. Using the first approach (using ring area), based on a load factor of 2, and a target reliability index T of 2.75 (calibratio n of LRFD resistance factors for geotechnical design in the st ate of Florida, W. A. Singletary), a -factor of .76 was obtained. Figure 7-3, shows the trends in -factor with variation in load factor, for different reliability index, using the entire cross-secti onal area in end bearing design. A load factor of 2, and a target reliability index T of 2.75, corresponds to a -factor of .61. Figure 7-4, plots the comp arison between measured vs. predicted capacity. The straight line running diagonally through the plots indicates ri = 1 (measured=predicted). Points lying below this line indicate a cons ervative design procedure, points lying in the

PAGE 103

85 zone above this line would indicate a higher predicted capacity than the measured one, and make our design an un-conservative one. Table 7-2. Measured vs. pr edicted capacity table. Sno Project Measured*Ring Area ** ri ** Full C/s *** ri *** 1 St. Georges Island Project 1050 803.92 1.31 1146.31 0.92 2 St. Georges Island Project 1400 1208.45 1.15 1604.15 0.87 3 St. Georges Island Project 1275 1081.69 1.17 1499.86 0.85 4 St. Georges Island Project 1425 834.08 1.71 1237.07 1.15 5 Chesapeake Bay Bridge LT-4 700 477.75 1.47 770.94 0.91 6 Chesapeake Bay Bridge LT-6 460 324.34 1.42 399.26 1.15 7 San Mateo Hayward Bridge 775 699.23 1.11 729.47 1.06 8 South Test-4 650 328.54 1.98 553.28 1.17 9 Woodrow Wilson Bridge 1475 1185.97 1.24 1600.36 0.92 10 Woodrow Wilson Bridge 1500 1230.65 1.22 1530.27 0.98 11 Woodrow Wilson Bridge 900 781.81 1.15 951.49 0.95 12 Salinas River Bridge 750 517.45 1.45 862.22 0.87 13 Port Of Oakland 27NC 625 462.39 1.35 544.57 1.15 14 Port Of Oakland 17NC1 512.5 439.08 1.17 592.09 0.87 15 Port Of Oakland 10NC1 450 400.47 1.12 598.50 0.75 16 Port Of Oakland 31NC 600 532.43 1.13 592.55 1.01 17 I-880 Oakland Site 3C 450 382.82 1.18 467.41 0.96 18 I-880 Oakland Site 3H 600 506.92 1.18 600.44 1.00 19 Santa Clara River Bridge 13 925 947.67 0.98 1205.60 0.77 20 Santa Clara River Bridge 7 1070 996.90 1.07 1436.45 0.74 21 Berenda Slough Br 4 800 702.77 1.14 798.97 1.00 Measured capacity in Tons. ** Capacity prediction using end be aring over the ring area in Tons. ***Capacity prediction using end bearing over th e entire cross sectional area in Tons. Table 7-3. Comparison of various statistical variables from the two approaches used in predicting capacity. Approach-1 (Ring Area) Approach-2 (Full C/S) r 1.27 0.955 r .23 .13 C.O.V .18 .13 .76 .61

PAGE 104

86 0 0.2 0.4 0.6 0.8 1 1.2 02468 QD/QL Figure 7-2. Resistance Factor vs. Dead to Li ve Load Ratio, Large Diameter Cylinder Pile with ring area. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 02468 QD/QL Figure 7-3. Resistance Factor vs. Dead to Li ve Load Ratio, Large Diameter Cylinder Pile with ring area.

PAGE 105

87 Measured Vs Predicted Capacity0 200 400 600 800 1000 1200 1400 1600 1800 2000 0200400600800100012001400160018002000 Measured Capacity (Tons)Predicted Capacity (Tons) Figure 7-4. Comparison of meas ured vs. predicted capacities.

PAGE 106

88 CHAPTER 8 RESULTS AND CONCLUSION 8.1 Finite Element Modeling of Soil Plug From the finite element study of the soil pl ug, it was evident that the inertial force on the soil plug is the most dominant feature, in the formation of the column of soil within the pile. Using the parametric study model the following were found to be most impacting: 1. Shell Thickness: There was a 40% increas e in the plug height (from 60% to 100%) when the shell thickness was reduced from 10” to 6”. This agrees with theory that larger the inertial force, higher the column of soil within the pile A pile with a 6” thick shell will have a larger inside volume as compared to a 10” thick pile (for the same outer diameter), and hence, a larg er inertia, causing the column of soil to remain at rest as the pile moves down into the soil, resulting in higher plug heights. 2. Rate of Penetration: There was a 15% increa se in the plug height when the rate of penetration was increased from 0.3inch/s ec to 0.5inch/sec. Higher the rate of penetration, higher the ‘g’ forces, and hen ce, higher the inertial forces (inertial force = mass of soil within number of ‘g’ forces). 3. Friction Angle: There was a 40% increase in the plug heights when the friction angle was reduced from 35degrees to 27.5degrees. 4. Outer Diameter: There was a 10% increase in the plug length, when the diameter was increased from 48” to 54” (same shell th ickness of 8”). This is in accordance of the theory of inertia as the inside volume of 54” diameter pile is greater than that of a 48” diameter pile. 5. Unit Weight: A 40pcf increase in the unit weight, from 80pcf to 120pcf, caused a 7% increase in the plug height. This is also in accordance with the theory of inertia, as the 120pcf soil mass has a larger inerti a as compared to a 80pcf soil mass, and would tend to retain its grounds a nd move up higher into the pile. 6. State of Soil: The dense sand was found to have slightly smaller plug heights as compared to loose sands. This was against the theory of inertia, as a dense soil mass would have higher iner tial forces as compared to a loose soil mass.

PAGE 107

89 Table 8-1. Inertia theory Vs finite elemen t modeling (arrows indica ting whether the plugs go up or down). Parameter Inertia Theory F.E.M Model Agreement Increase shell thickness Agree Increase rate of penetration Agree Increase friction Angle Agree Increase outer diameter Agree Increase unit weight Agree Higher for loose sand or dense sandDense sand Loose Sand Disagree The finite element application ADINA, was unable to model geotechnical problems such as pile driving, and hence a new approach of combining the ADINA pile model and ADINA-F soil model, using the ADINA-FSI was used. The loose sands, and the dense sands, were modeled using the compressible, and slightly compressible models respectively. Th ese models may not have been, an equally good representation to soils, as they are to fl uids, causing a disagreement with the “Inertia theory”. The plug heights could not be determin ed exactly because the VR (Velocity Ratio) was never completely equal to 1.0, indicating a small relative movement between the soil plug and the pile. This could be b ecause of the difference in the way the interface is modeled using ADINA-FSI, a nd the real field condition. 8.2 Evaluating Unit Sk in and Tip Resistance These equations were formed by, fitting the best-fit line through the data points. In the absence of sufficient data, for steel piles in silt the curves could not be developed. In calculating the total capacity of the pile, the skin friction should be computer over the

PAGE 108

90 outer surface of the pile, and end bearing co mputer over the ring cro ss sectional area of the pile tip. Table 8-2. Skin friction and tip resistance e quations (in terms of uncorrected SPT blow counts), developed using the piles in the UF/FDOT cylinder pile database. No Soil Type Skin Friction (tsf) End Bearing (tsf) Concrete .5083*().634fsLnN 5 < N < 60 1 Plastic clays Steel .4236*ln().5404fsN 5 < N < 60 N qt* 2226 2 Clay-siltsand mixtures Concrete .3265*().2721 fsLnN 5 < N < 60 N qt 4101 Concrete .3048*ln().4599fsN 5 < N < 60 3 Clean sands Steel .2028*().2646 fsLnN 5 < N < 60 N qt* 5676 8.3 LRFD Study Based on the equations developed for unit sk in friction, and unit end bearing, the capacities of the piles were pr edicted based on their soil ty pe, and uncorrected SPT blow counts. These were compared to capacities of the piles measured in the field. A -factor of 0.73 was obtained for a reliabilit y index of 2.75 (based on AASHTO’s recommendation of using a probability of failu re between .1 and .01 for driven piles, 1994). 8.4 Recommendations Based on results from this research, th e following recommendations are made: More load test needed for so ils of higher blow counts. More data needed from strain gages. Effect of pile freeze on large diamet er pile needs to be studied.

PAGE 109

91 APPENDIX A DATA REDUCTION AND DATABASE Table A-1. Current Database entry and description. S.No Project Name # O.D* T* L* Le* Material 1 St. Georges Island Project 59 54-inch 8-inch 80-ft 51-ft Concrete 2 St. Georges Island Project 60 54-inch 8-inch 80-ft 46-ft Concrete 3 St. Georges Island Project 61 54-inch 8-inch 80-ft 59.5-ft Concrete 4 St. Georges Island Project 62 54-inch 8-inch 80-ft 46.7-ft Concrete 5 Chesapeake Bay Bridge 52 54-inch 6-inch 184-ft 139.7-ft Concrete 6 Chesapeake Bay Bridge 53 54-inch 6-inch 146.9-ft 104.88-ft Concrete 7 Chesapeake Bay Bridge 55 54-inch 6-inch 172-ft 77.17-ft Concrete 8 Chesapeake Bay Bridge 56 66-inch 6-inch 200-ft 94-ft Concrete 9 Chesapeake Bay Bridge 57 66-inch 6-inch 204-ft 105-ft Concrete 10 Chesapeake Bay Bridge 58 54-inch 6-inch 128-ft 44-ft Concrete 11 San Mateo Hayward Bridge 92 42-inch 6.9-inch 42.25-m 35.31-mtr Concrete 12 San Mateo Hayward Bridge 93 42-inch 6.9-inch 40.8-m 26.5-mtr Concrete 13 Oregon Inlet 50 66-inch 6-inch 130.5-ft 71.5-ft Concrete 14 I-664 Bridge North 51 54-inch 5-inch 104-ft 68.4-ft Concrete 15 South Test-4 66 54-inch 5-inch 47.9-ft 27-ft Concrete 16 South Test-5 67 54-inch 5-inch 93.3-ft 68.4-ft Concrete 17 South Test-6 68 54-inch 5-inch 96.3-ft 73.67-ft Concrete 18 South Test-10 69 54-inch 5-inch 172-ft 145.1-ft Concrete 19 South Test-11 70 54-inch 5-inch 143-ft 115.3-ft Concrete 20 South Test-12 71 54-inch 5-inch 133.17-ft 95.9-ft Concrete 21 South Test-13 72 54-inch 5-inch 125.33-ft 88.9-ft Concrete 22 South Test-14 73 54-inch 5-inch Concrete 23 Woodrow Wilson Bridge 63 54-inch 1-inch 164-ft 132.2-ft Steel 24 Woodrow Wilson Bridge 64 42-inch 1-inch 125-ft 107-ft Steel 25 Woodrow Wilson Bridge 65 36-inch 1-inch 96-ft 90.6-ft Steel 26 Salinas River Bridge 81 72-inch .75-inch 114-ft Steel 27 Port Of Oakland 27NC 82 42-inch .625-inch 91.5-ft Concrete 28 Port Of Oakland 17NC1 83 42-inch .75-inch 98.8-ft Concrete 29 Port Of Oakland 10NC1 84 42-inch .75-inch 94-ft Concrete 30 Port Of Oakland 31NC 85 42-inch .625-inch 91.5-ft Concrete 31 I-880 Oakland Site 3C 86 42-inch .75-inch 100.5-ft 83.5-ft Steel 32 I-880 Oakland Site 3H 87 42-inch .75-inch 100.5-ft 83.5-ft Steel 33 Santa Clara River Bridge 13 88 72-inch 1.5-inch 135.136-ft 114.472-ft Steel 34 Santa Clara River Bridge 89 84-inch 1.74-inch 66.256-ft 52.48-ft Steel 35 Berenda Slough Br 4 90 42-inch .625-inch 101.68-ft Steel

PAGE 110

92 #: UF/FDOT Database entry number. O.D: Outer diameter. t: Shell thickness. L: Total length. Le: Embedded length. Table A-2. Soil type, ins itu test, and plug status. Sno Project Name Soil Type Skin Soil Type End Insitu Test Plug Status 1 St. Georges Island Project Sand Limestone SPT/CPT Unplugged 2 St. Georges Island Project Sand Limestone SPT/CPT Unplugged 3 St. Georges Island Project Sand Limestone SPT/CPT Unplugged 4 St. Georges Island Project Sand Limestone SPT/CPT Unplugged 5 Chesapeake Bay Bridge Silt Silt CPT/SPT Plugged 6 Chesapeake Bay Bridge Silt Silt CPT/SPT Unplugged 7 Chesapeake Bay Bridge Silt Silt CPT/SPT Unplugged 8 Chesapeake Bay Bridge Sand Sand CPT/SPT Plugged 9 Chesapeake Bay Bridge Sand Sand CPT/SPT Plugged 10 Chesapeake Bay Bridge Sand Sand SPT Plugged 11 San Mateo Hayward Bridge Silt Silt SPT Unplugged 12 San Mateo Hayward Bridge Silt Silt SPT Unplugged 13 Oregon Inlet Silt Silt CPT/SPT Unplugged 14 I-664 Bridge North Clay Clay SPT Unplugged 15 South Test-4 Sands Sands SPT Unplugged 16 South Test-5 Sands Sands SPT Unplugged 17 South Test-6 Sands Sands SPT Unplugged 18 South Test-10 Sands Sands SPT Unplugged 19 South Test-11 Sands Sands SPT Unplugged 20 South Test-12 Sands Sands SPT Unplugged 21 South Test-13 Sands Sands SPT Unplugged 22 South Test-14 Sands Sands SPT Unplugged 23 Woodrow Wilson Bridge Sands Clays SPT Unplugged 24 Woodrow Wilson Bridge Sands Clays SPT Unplugged 25 Woodrow Wilson Bridge Sands Clays SPT Unplugged 26 Salinas River Bridge Clays Clays SPT Unplugged 27 Port Of Oakland 27NC Clay Clays SPT Unplugged 28 Port Of Oakland 17NC1 Clay Clays SPT Unplugged 29 Port Of Oakland 10NC1 Clay Clays SPT Unplugged 30 Port Of Oakland 31NC Clay Clays SPT Unplugged 31 I-880 Oakland Site 3C Clay Clays SPT Plugged 32 I-880 Oakland Site 3H Clay Clay SPT Plugged 33 Santa Clara River Bridge 13 Sand Sands SPT Plugged 34 Santa Clara River Bridge 7 Sand Sands SPT Plugged 35 Berenda Slough Br 4 Silts Silts SPT Unplugged

PAGE 111

93 Table A-3. Data used for concrete piles in sand. N fs D* Project Name #* 6.15625 0.088189752 66 Chesapeake Bay LT-5 57 9.4230769 0.109994345 54 Chesapeake Bay LT-3 55 10.342105 0.160078473 66 Chesapeake Bay LT-4 56 11.25 0.18 54 I-664 Test-4 DeBeer’s 66 21.25 0.45 54 Chesapeake Bay LT-6 58 35.307692 0.6 54 I-664 Test-14 DeBeer’s 73 Table A-4. Data used for steel piles in sand. N fs D* Project Name # 14.33 0.224934149 54 Woodrow Wilson-C 63 35.375 0.633 36 Woodrow Wilson-I 65 43 0.529292342 54 Woodrow Wilson-C 63 48.2 0.535064525 54 Woodrow Wilson-C DeBeer’s 63 50.172 0.934955607 42 Woodrow Wilson-F DeBeer’s 64 80 1 36 Woodrow Wilson-I 65 85 1.15 42 Woodrow Wilson-F 64 91.33 1.65 42 Woodrow Wilson-F 64 N: Uncorrected SPT blow count. fs: Skin friction in tsf. D: Outer diameter of the pile. #: UF/FDOT database entry number. Table A-5. Data used for concrete piles in clay. N fs D Project Name # 10.27 0.20253552 54 Chesapeake Bay LT-1 52 10.3 0.245123125 54 I-664 Test-7 DeBeer’s 66 10.5 0.387002901 42 Oakland 10 NC1 84 12.20588 0.3 54 Chesapeake Bay LT-2 53 16.4 0.521819486 42 Oakland 31NC 85 19.33 0.596365126 42 Oakland 27NC 82 23.25 1.02 42 Oakland 17NC-1 83 Table A-6. Data used for steel piles in clay. N fs D Project Name # 55.25 1.2 54 Woodrow Wilson-C 63 49 1.15 42 Woodrow Wilson-F 64 29 0.85 42 Woodrow Wilson-F 64 10.4 0.381209445 42 I-880 3C 86 10.4 0.353980198 42 I-880 3H 87 10 0.397093171 72 Salinas River Bridge 81

PAGE 112

94 Table A-7. Data used for concrete piles in silt. N fs D Project Name # 3.6 0.033382 54 St. Georges LT-1 59 4.875 0.120239 54 St. Georges LT-3 61 8 0.22441 54 St. Georges LT-2 60 9.423077 0.109994 54 Chesapeake Bay LT-3 55 17.75 0.445944 54 St. Georges LT-4 62 18.67 0.344521 54 St. Georges LT-2 60 22.22 0.549678 San Mateo Hayward A 22.7 0.57 54 St. Georges LT-4 62 23.4 0.52 54 St. Georges LT-3 61 N: Uncorrected SPT blow count. fs: Skin friction in tsf. D: Outer diameter of the pile. #: UF/FDOT database entry number. Table A-8. Data used for the end bearing in sand. N Qt D Project Name # Material 50 30 66 Chesapeake Bay LT-4 56 Concrete 51 33.0199 54 I-664 Test-4 DeBeer's 66 Concrete 23 16.79968844 72 Santa Clara 13-1 88 Steel 27 24.667 42 Berenda Slough 90 Steel 28.5 22.10485321 72 Santa Clara 13-2 88 Steel 29 13.2001161 84 Santa Clara 7-1 89 Steel 55.33 30.5764579 84 Santa Clara 7-2 89 Steel 100 51.96 42 Woodrow Wilson-F DeBeer’s 64 Steel 100 55 42 Woodrow Wilson-F 64 Steel Table A-9. Data used fo r end bearing in silt. N Qt D Project Name # Material 14.5 5.196896 42 Oakland 10NC-1 84 Steel 22 7.795344 92 San Mateo Hayward Bridge 92 Concrete 29 13.20012 84 Santa Clara 7-1 89 Steel 50 30 66 Chesapeake Bay LT-4 56 Concrete 55.33 30.57646 84 Santa Clara 7-2 89 Steel Table A-10. Data used for end bearing in clay. N Qt D Project Name # Material 3 1.1 42 Oakland 17NC-1 84 Steel 14.25 3.27 72 Salinas River Bridge 81 Steel 16.4 3.65 42 Oakland 31NC 85 Steel 18 4 42 I-880 3C 86 Steel

PAGE 113

95 0 500 1000 1500 2000 2500 3000 3500 4000 00.20.40.60.811.21.41.61.822.22.42.62.833.23.43.63.84 displacement inchload tons 1 10 100 1000 10000 0.010.1110 log disp inchlog load tons St. Georges Island Bridge Replacement Project LT-1 Skin Friction Capacity 850 Tons End Bearing Capacity 200 Tons FDOT Capacity 1050 Tons Figure A-1. St. Georges Island Br idge Replacement Project LT-1.

PAGE 114

96 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 00.20.40.60.811.21.41.61.822.22.42.62.8 disp inchload tons 1 10 100 1000 10000 0.010.1110 log disp inchlog load tons St. Georges Island Bridge Replacement Project LT-4. Skin Friction Capacity 1300 Tons End Bearing Capacity 200 Tons FDOT Capacity 1500 Tons Figure A-2. St. Georges Island Br idge Replacement Project, LT-4.

PAGE 115

97 0 200 400 600 800 1000 1200 1400 1600 1800 2000 00.20.40.60.811.21.41.61.822.22.42.62.833.23.43.63.84 deflection inchload tons 1 10 100 1000 0.0010.010.11 log disp inchlog load tons Chesapeake Bay LT-1. Skin Friction Capacity N.A (not taken to failure) End Bearing Capacity N.A (not taken to failure) Figure A-3. Chesapeake Bay LT-1.

PAGE 116

98 0 500 1000 1500 2000 2500 3000 00.20.40.60.811.21.41.61.822.22.42.62.833.23.43.63.84 Deflection (inch)Load (Tons) 1 10 100 1000 0.0010.010.11 log disp inchlog load tons Chesapeake Bay LT-2. Skin Friction Capacity N.A (not taken to failure) End Bearing Capacity N.A (not taken to failure) Figure A-4. Chesapeake Bay LT-2.

PAGE 117

99 0 100 200 300 400 500 600 700 800 900 1000 00.20.40.60.811.21.41.61.822.22.42.62.83 Disp (inch)Load (Tons) 1 100 10000 0.010.1110 Log DispLog Load y Chesapeake Bay LT-6. Skin Friction Capacity 300 Tons End Bearing Capacity 150 Tons FDOT Capacity 450 Tons Figure A-5. Chesapeake Bay LT-6.

PAGE 118

100 0 200 400 600 800 1000 1200 1400 1600 1800 00.30.60.91.21.51.82.12.42.73disp (inch)load (tons) 1 100 10000 0.010.1110Log Movement (inch)Log Load (kips) San Mateo Hayward BridgeA. Skin Friction Capacity 700 Tons End Bearing Capacity 75 Tons FDOT Capacity 775 Tons Figure A-6. San Mate o Hayward Bridge-A.

PAGE 119

101 0 200 400 600 800 1000 1200 00.511.522.53 disp (inch)Load (tons) 1 100 10000 0.010.1110 disp (inch)load (tons) I-664 Bridge Test-4. Skin Friction Capacity 400 Tons End Bearing Capacity 250 Tons FDOT Capacity 650 Tons Figure A-7. I-664 Bridge Test-4.

PAGE 120

102 0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475 500 525 550 575 600 625 650 675 700 00.40.81.21.622.42.8 disp inchload tons 1 10 100 1000 0.010.1110 log disp inchlog load tons I-664 Bridge Test-7. Skin Friction Capacity 350 Tons End Bearing Capacity 125 Tons FDOT Capacity 475 Tons Figure A-8. I-664 Bridge Test-7.

PAGE 121

103 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 16000.00.40.81.21.62.02.42.83.23.64.0disp (inch)load (tons) 1 100 10000 0.00.00.11.010.0log displog load Woodrow Wilson Bridge-C. Skin Friction Capacity 1000 Tons End Bearing Capacity 475 Tons FDOT Capacity 1475 Tons Figure A-9. Woodrow Wilson Bridge-C.

PAGE 122

104 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 00.511.522.533.54disp inchload tons 1 10 100 1000 10000 0.0010.010.1110 log disp inchlog load tons Woodrow Wilson Bridge-F. Skin Friction Capacity 1000 Tons End Bearing Capacity 500 Tons FDOT Capacity 1500 Tons Figure A-10. Woodrow Wilson Bridge-F.

PAGE 123

105 0 100 200 300 400 500 600 700 800 900 1000 00.10.20.30.40.50.60.70.8 Disp (inch)Load (Tons) 1 10 100 1000 0.010.11 Log Disp (inch)Log Load (Tons) Woodrow Wilson Bridge-I. FDOT Capacity 900Tons Figure A-11. Woodrow Wilson Bridge-I.

PAGE 124

106 0 200 400 600 800 1000 1200 00.10.20.30.40.50.60.7 Deflection (in)Load (Tons) 1 10 100 1000 10000 0.010.11 Log d(inch)Log load (tons) Oregon Inlet. Skin Friction Capacity N.A (not taken to failure) End Bearing Capacity N.A (not taken to failure) Figure A-12. Oregon Inlet.

PAGE 125

107 0 100 200 300 400 500 600 700 800 900 00.511.522.533.5 disp (inch)load (tons) 100 1000 0.010.11 log displog load Salinas River Bridge Skin Friction Capacity 600 Tons End Bearing Capacity 150 Tons FDOT Capacity 750 Tons Figure A-13. Salinas River Bridge.

PAGE 126

108 0 100 200 300 400 500 600 700 00.511.522.5 disp (inch)load (tons) 100 1000 0.1 1 log displog load Port of Oakland Bridge 27NC. Skin Friction Capacity 550Tons End Bearing Capacity 75 Tons FDOT Capacity 625 Tons Figure A-14. Port of Oakland Bridge 27NC.

PAGE 127

109 0 50 100 150 200 250 300 350 400 450 500 550 600 650 00.20.40.60.811.21.41.61.82 100 1000 0.1 1 log disp inchlog load tons Port of Oakland Bridge 10NC. Skin Friction Capacity 400Tons End Bearing Capacity 50 Tons FDOT Capacity 450 Tons Figure A-15. Port of Oakland Bridge 10NC.

PAGE 128

110 0 100 200 300 400 500 600 700 00.511.52 disp inchload tons 100 1000 0.1 1 log disp inchlog load tons Port of Oakland Bridge 17NC. Skin Friction Capacity 475 Tons End Bearing Capacity 37.5 Tons FDOT Capacity 512.5 Tons Figure A-16. Port of Oakland Bridge 17NC.

PAGE 129

111 0 50 100 150 200 250 300 350 400 450 500 550 600 650 00.511.522.53 disp inchload tons 100 1000 0.1 1 log disp inchlog load tons Port of Oakland Bridge 31NC. Skin Friction Capacity 525 Tons End Bearing Capacity 75 Tons FDOT Capacity 600 Tons Figure A-17. Port of Oakland Bridge 31NC.

PAGE 130

112 0 100 200 300 400 500 600 700 00.511.52 disp (inch)load (tons) 1 10 100 1000 0.010.11 log displog load I-880 Bridge 3H. Skin Friction Capacity 325 Tons End Bearing Capacity 275 Tons FDOT Capacity 600 Tons Figure A-18. I-880 Bridge 3H.

PAGE 131

113 0 50 100 150 200 250 300 350 400 450 500 550 600 00.20.40.60.811.21.41.61.82 disp inchload tons FHWA=450 Tons 1 10 100 1000 0.010.11 log disp inchlog load tons I-880 Bridge 3C. Skin Friction Capacity 350 Tons End Bearing Capacity 100 Tons FDOT Capacity 450 Tons Figure A-19. I-880 Bridge 3C.

PAGE 132

114 0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 00.511.522.533.5disp (inch)load (tons) 100 1000 10000 0.1110 disp (inch)load (tons) Santa Clara River Bridge Pier-7. Skin Friction Capacity 600 Tons End Bearing Capacity 500 Tons FDOT Capacity 1100 Tons Figure A-20. Santa Clara River Bridge Pier-7.

PAGE 133

115 0 200 400 600 800 1000 1200 00.511.522.533.544.555.566.577.58 disp inchload tons 100 1000 0.010.1110 Santa Clara River Bridge Pier-13. Skin Friction Capacity 600 Tons End Bearing Capacity 325 Tons Figure A-21. Santa Clara River Bridge Pier-13.

PAGE 134

116 0 100 200 300 400 500 600 700 800 900 00.511.522.5 100 1000 0.1110 log disp inchlog load tons Santa Clara River Bridge Pier-13. Skin Friction Capacity 500 Tons End Bearing Capacity 300 Tons Figure A-22. Santa Clara River Bridge Pier-13.

PAGE 135

117 APPENDIX B ADINA ANALYSIS OF SOIL PLUG Table B-1. Symbols used in finite element parametric study. D Outer diameter of pile t Shell thickness of pile PL Plug length %PL (PL*100) /Length of pile Velocity at the Node Individual velocities at nodes 551 through 560 Total Total of velocities 551 through 560 Avg Average of veloci ties at nodes 551 through 560 Max Velocity of the pile, maximum velocity in the system Ratio = (1/PLR) Maximum velocity divided by average velocity = 70 Friction angle in terms of viscosity of soil PLR Plug length ratio = plug length / pile penetration

PAGE 136

118Table B-2. Velocity of plug with variation in ratio of diameter to shell thickness for loose sand. D-t PL % PL* Velocity at Node* Tota l* Avg Max Ratio* 551 552 553 554 555 556 557 558 559 560 60-10 58 72.5 1.27 E-02 9.22 E-03 7.19 E-03 5.61 E-03 4.32 E-03 3.25 E-03 2.36 E-03 1.61 E-03 9.81 E-04 4.49 E-04 4.77 E-02 4.77 E-03 3.33 E-01 69.8647 54-8 68 85 1.27 E-02 9.26 E-03 7.22 E-03 5.63 E-03 4.33 E-03 3.25 E-03 2.36 E-03 1.61 E-03 9.79 E-04 4.48 E-04 4.78 E-02 4.78 E-03 3.35 E-01 70.114 48-8 61 76.25 1.27 E-02 9.24 E-03 7.21 E-03 5.62 E-03 4.33 E-03 3.26 E-03 2.36 E-03 1.61 E-03 9.80 E-04 4.49 E-04 4.77 E-02 4.77 E-03 3.37 E-01 70.6848 36-6 63 78.75 1.24 E-02 9.10 E-03 7.12 E-03 5.56 E-03 4.28 E-03 3.22 E-03 2.34 E-03 1.60 E-03 9.71 E-04 4.45 E-04 4.70 E-02 4.70 E-03 3.42 E-01 72.6575 62 77.5 1.26 E-02 9.23 E-03 7.22 E-03 5.64 E-03 4.34 E-03 3.27 E-03 2.37 E-03 1.62 E-03 9.86 E-04 4.52 E-04 4.77 E-02 4.77 E-03 3.42 E-01 71.5827 Table B-3. Velocity of plug with va riation in ratio of diameter to sh ell thickness in case of dense sand. D-t* PL %PL* Velocity at Node* Tota l* Avg Max*Ratio* 551 552 553 554 555 556 557 558 559 560 60-10 56 70 1.29 E-02 9.58 E-03 7.60 E-03 6.02 E-03 4.69 E-03 3.57 E-03 2.62 E-03 1.80 E-03 1.10 E-03 5.08 E-04 5.04 E-02 5.04 E-03 3.52E -01 69.8053 54-8 66 82.5 1.29 E-02 9.63 E-03 7.63 E-03 6.03 E-03 4.69 E-03 3.57 E-03 2.61 E-03 1.79 E-03 1.10 E-03 5.06 E-04 5.05 E-02 5.05 E-03 3.54E -01 70.1757 48-8 59 73.75 1.30 E-02 9.72 E-03 7.71 E-03 6.09 E-03 4.75 E-03 3.61 E-03 2.64 E-03 1.82 E-03 1.11 E-03 5.12 E-04 5.10 E-02 5.10 E-03 3.57E -01 70.0067 36-6 60 75 1.31 E-02 9.84 E-03 7.81 E-03 6.18 E-03 4.81 E-03 3.65 E-03 2.67 E-03 1.84 E-03 1.13 E-03 5.18 E-04 5.16 E-02 5.16 E-03 3.62E -01 70.26

PAGE 137

119Table B-4. Velocity of plug with variation in rate of penetrat ion of the pile for loose sand. Tractio n PL %PL* Velocity at Node* Tota l* Avg* Max Ratio* 551 552 553 554 555 556 557 558 559 560 100tsf 68 85 1.27 E-02 9.26 E-03 7.22 E-03 5.63 E-03 4.33 E-03 3.25 E-03 2.36 E-03 1.61 E-03 9.79 E-04 4.48 E-04 4.78 E-02 4.78E -03 3.35 E-01 70.1140 4 75tsf 65 81.25 1.03 E-02 7.54 E-03 5.88 E-03 4.59 E-03 3.53 E-03 2.66 E-03 1.93 E-03 1.32 E-03 8.02 E-04 3.67 E-04 3.90 E-02 3.90E -03 2.77 E-01 71.0554 2 64 80 1.05 E-02 7.64 E-03 5.96 E-03 4.65 E-03 3.58 E-03 2.70 E-03 1.96 E-03 1.34 E-03 8.14 E-04 3.72 E-04 3.95 E-02 3.95E -03 2.77 E-01 70.0839 1 50tsf 60 75 7.75 E-03 5.66 E-03 4.43 E-03 3.46 E-03 2.67 E-03 2.01 E-03 1.46 E-03 9.98 E-04 6.08 E-04 2.78 E-04 2.93 E-02 2.93E -03 2.10 E-01 71.6245 4 59 73.75 7.86 E-03 5.74 E-03 4.49 E-03 3.51 E-03 2.71 E-03 2.04 E-03 1.48 E-03 1.01 E-03 6.18 E-04 2.83 E-04 2.98 E-02 2.98E -03 2.10 E-01 70.5667 5 Table B-5. Velocity of plug with variation in rate of penetrat ion of the pile for dense sand. Tractio n PL % PL* Velocity at Node* Tota l* Avg* Max Ratio* 551 552 553 554 555 556 557 558 559 560 100tsf 66 82.5 1.29 E-02 9.63 E-03 7.63 E-03 6.03 E-03 4.69 E-03 3.57 E-03 2.61 E-03 1.79 E-03 1.10 E-03 5.06 E-04 5.05 E-02 5.05E -03 3.54 E-01 70.1212 4 75tsf 62 77.5 1.06 E-02 7.91 E-03 6.28 E-03 4.97 E-03 3.87 E-03 2.94 E-03 2.16 E-03 1.48 E-03 9.09 E-04 4.19 E-04 4.15 E-02 4.15E -03 2.91 E-01 70.8610 1 50tsf 57 71.25 7.92 E-03 5.91 E-03 4.70 E-03 3.72 E-03 2.91 E-03 2.21 E-03 1.62 E-03 1.12 E-03 6.85 E-04 3.16 E-04 3.11 E-02 3.11E -03 2.20 E-01 70.1212 4

PAGE 138

120Table B-6. Velocity of plug with varia tion in density of soil for loose sand. Densit y* PL %PL* Velocity at Node Tota l Avg Max Ratio 551 552 553 554 555 556 557 558 559 560 80pcf 65 81.25 1.37 E-02 9.96 E-03 7.77 E-03 6.06 E-03 4.67 E-03 3.51 E-03 2.55 E-03 1.74 E-03 1.06 E-03 4.85 E-04 5.15 E-02 5.15E -03 3.61 E-01 70.1 100pcf 68 85 1.27 E-02 9.26 E-03 7.22 E-03 5.63 E-03 4.33 E-03 3.25 E-03 2.36 E-03 1.61 E-03 9.79 E-04 4.48 E-04 4.78 E-02 4.78E -03 3.35 E-01 70.1 120pcf 71 88.75 1.19 E-02 8.63 E-03 6.72 E-03 5.23 E-03 4.02 E-03 3.02 E-03 2.19 E-03 1.49 E-03 9.07 E-04 4.15 E-04 4.45 E-02 4.45E -03 3.14 E-01 70.7 Table B-7. Velocity of plug with varia tion in density of soil for dense sand. Densit y* PL %PL* Velocity at Node Tota l Avg Max Ratio 551 552 553 554 555 556 557 558 559 560 58 72.5 1.48 E-02 1.11 E-02 8.80 E-03 6.97 E-03 5.44 E-03 4.14 E-03 3.03 E-03 2.09 E-03 1.28 E-03 5.89 E-04 5.82 E-02 5.82E -03 3.80 E-01 65.2955 5 59 73.75 1.46 E-02 1.09 E-02 8.67 E-03 6.86 E-03 5.35 E-03 4.07 E-03 2.98 E-03 2.05 E-03 1.26 E-03 5.80 E-04 5.74 E-02 5.74E -03 3.80 E-01 66.2665 6 62 77.5 1.40 E-02 1.05 E-02 8.30 E-03 6.57 E-03 5.12 E-03 3.89 E-03 2.85 E-03 1.96 E-03 1.20 E-03 5.54 E-04 5.50 E-02 5.50E -03 3.80 E-01 69.1887 5 80pcf 63 78.75 1.38 E-02 1.03 E-02 8.19 E-03 6.48 E-03 5.05 E-03 3.84 E-03 2.81 E-03 1.93 E-03 1.18 E-03 5.45 E-04 5.42 E-02 5.42E -03 3.80 E-01 70.1724 6 100pcf 66 82.5 1.29 E-02 9.63 E-03 7.63 E-03 6.03 E-03 4.69 E-03 3.57 E-03 2.61 E-03 1.79 E-03 1.10 E-03 5.06 E-04 5.05 E-02 5.05E -03 3.54 E-01 70.1756 8 120pcf 69 86.25 1.21 E-02 9.00 E-03 7.13 E-03 5.63 E-03 4.38 E-03 3.32 E-03 2.43 E-03 1.67 E-03 1.02 E-03 4.71 E-04 4.72 E-02 4.72E -03 3.34 E-01 70.7722 7

PAGE 139

121Table B-8. Velocity of plug with variation of shear strength in case of loose sand. PL %PL* Velocity at Node* Tota l* Avg* Max Ratio* 551 552 553 554 555 556 557 558 559 560 10 12.5 3.54 E-02 2.96 E-02 2.65 E-02 2.34 E-02 1.99 E-02 1.64 E-02 1.28 E-02 9.31 E-03 5.99 E-03 2.88 E-03 1.82 E-01 1.82E -02 3.35 E-01 18.40 20 25 3.01 E-02 2.27 E-02 1.87 E-02 1.54 E-02 1.24 E-02 9.75 E-03 7.32 E-03 5.14 E-03 3.20 E-03 1.49 E-03 1.26 E-01 1.26E -02 3.35 E-01 26.56 40 50 1.97 E-02 1.44 E-02 1.14 E-02 8.98 E-03 6.99 E-03 5.31 E-03 3.88 E-03 2.67 E-03 1.63 E-03 7.49 E-04 7.57 E-02 7.57E -03 3.35 E-01 44.27 60 75 1.42 E-02 1.03 E-02 8.07 E-03 6.30 E-03 4.86 E-03 3.66 E-03 2.66 E-03 1.81 E-03 1.10 E-03 5.06 E-04 5.35 E-02 5.35E -03 3.35 E-01 62.69 70 87.5 1.24 E-02 9.02 E-03 7.03 E-03 5.48 E-03 4.21 E-03 3.17 E-03 2.29 E-03 1.56 E-03 9.52 E-04 4.35 E-04 4.65 E-02 4.65E -03 3.35 E-01 72.00 1000 80 100 1.10 E-02 8.00 E-03 6.22 E-03 4.84 E-03 3.72 E-03 2.79 E-03 2.02 E-03 1.38 E-03 8.36 E-04 3.82 E-04 4.12 E-02 4.12E -03 3.35 E-01 81.39 10 12.5 2.63 E-02 2.20 E-02 1.97 E-02 1.74 E-02 1.48 E-02 1.22 E-02 9.51 E-03 6.92 E-03 4.45 E-03 2.14 E-03 1.35 E-01 1.35E -02 2.91 E-01 21.46 20 25 2.23 E-02 1.69 E-02 1.39 E-02 1.14 E-02 9.23 E-03 7.24 E-03 5.44 E-03 3.82 E-03 2.38 E-03 1.11 E-03 9.36 E-02 9.36E -03 2.91 E-01 31.02 40 50 1.45 E-02 1.07 E-02 8.44 E-03 6.66 E-03 5.19 E-03 3.94 E-03 2.88 E-03 1.98 E-03 1.21 E-03 5.57 E-04 5.61 E-02 5.61E -03 2.90 E-01 51.77 60 75 1.05 E-02 7.65 E-03 5.98 E-03 4.67 E-03 3.60 E-03 2.72 E-03 1.97 E-03 1.35 E-03 8.21 E-04 3.76 E-04 3.96 E-02 3.96E -03 2.90 E-01 73.30 70 87.5 9.15 E-03 6.68 E-03 5.21 E-03 4.06 E-03 3.13 E-03 2.35 E-03 1.70 E-03 1.16 E-03 7.08 E-04 3.24 E-04 3.45 E-02 3.45E -03 2.90 E-01 84.22 1500 80 100 8.12 E-03 5.92 E-03 4.61 E-03 3.59 E-03 2.76 E-03 2.07 E-03 1.50 E-03 1.02 E-03 6.22 E-04 2.84 E-04 3.05 E-02 3.05E -03 2.90 E-01 95.23 2000 10 12.5 2.08 E-02 1.74 E-02 1.56 E-02 1.38 E-02 1.17 E-02 9.64 E-03 7.53 E-03 5.48 E-03 3.52 E-03 1.69 E-03 1.07 E-01 1.07E -02 2.58 E-01 24.05

PAGE 140

122Table B-8 continued 20 25 1.76 E-02 1.33 E-02 1.10 E-02 9.03 E-03 7.31 E-03 5.73 E-03 4.31 E-03 3.02 E-03 1.88 E-03 8.78 E-04 7.41 E-02 7.41E -03 2.58 E-01 34.79 40 50 1.15 E-02 8.46 E-03 6.68 E-03 5.27 E-03 4.10 E-03 3.12 E-03 2.28 E-03 1.57 E-03 9.59 E-04 4.41 E-04 4.44 E-02 4.44E -03 2.58 E-01 58.08 60 75 8.28 E-03 6.05 E-03 4.73 E-03 3.70 E-03 2.85 E-03 2.15 E-03 1.56 E-03 1.07 E-03 6.50 E-04 2.98 E-04 3.13 E-02 3.13E -03 2.58 E-01 82.24 70 87.5 6.42 E-03 4.68 E-03 3.65 E-03 2.84 E-03 2.18 E-03 1.64 E-03 1.19 E-03 8.09 E-04 4.92 E-04 2.25 E-04 2.41 E-02 2.41E -03 2.58 E-01 106.86 80 100 6.42 E-03 4.68 E-03 3.65 E-03 2.84 E-03 2.18 E-03 1.64 E-03 1.19 E-03 8.09 E-04 4.92 E-04 2.25 E-04 2.41 E-02 2.41E -03 2.58 E-01 106.86 Table B-9. Velocity of plug with variation in shear stre ngth in case of dense sand. PL %PL* Velocity at Node* Tota l* Avg* Max Ratio* 551 552 553 554 555 556 557 558 559 560 10 12.5 3.31 E-02 2.78 E-02 2.49 E-02 2.19 E-02 1.87 E-02 1.54 E-02 1.20 E-02 8.72 E-03 5.60 E-03 2.69 E-03 1.71 E-01 1.71E -02 3.54 E-01 20.74 20 25 2.72 E-02 2.09 E-02 1.73 E-02 1.44 E-02 1.17 E-02 9.18 E-03 6.92 E-03 4.87 E-03 3.04 E-03 1.42 E-03 1.17 E-01 1.17E -02 3.54 E-01 30.31 40 50 1.75 E-02 1.31 E-02 1.05 E-02 8.34 E-03 6.55 E-03 5.02 E-03 3.69 E-03 2.55 E-03 1.57 E-03 7.24 E-04 6.95 E-02 6.95E -03 3.54 E-01 50.97 60 75 1.25 E-02 9.34 E-03 7.41 E-03 5.86 E-03 4.56 E-03 3.47 E-03 2.54 E-03 1.74 E-03 1.07 E-03 4.92 E-04 4.90 E-02 4.90E -03 3.54 E-01 72.27 70 87.5 1.10 E-02 8.16 E-03 6.45 E-03 5.09 E-03 3.96 E-03 3.00 E-03 2.20 E-03 1.51 E-03 9.23 E-04 4.25 E-04 4.27 E-02 4.27E -03 3.54 E-01 82.98 1000 80 100 9.73 E-03 7.23 E-03 5.72 E-03 4.50 E-03 3.50 E-03 2.65 E-03 1.94 E-03 1.33 E-03 8.13 E-04 3.74 E-04 3.78 E-02 3.78E -03 3.54 E-01 93.74

PAGE 141

12310 12.5 2.43 E-02 2.04 E-02 1.83 E-02 1.61 E-02 1.37 E-02 1.13 E-02 8.79 E-03 6.39 E-03 4.11 E-03 1.97 E-03 1.25 E-01 1.25E -02 3.05 E-01 24.34 20 25 1.99 E-02 1.53 E-02 1.27 E-02 1.05 E-02 8.54 E-03 6.73 E-03 5.07 E-03 3.57 E-03 2.23 E-03 1.04 E-03 8.56 E-02 8.56E -03 3.05 E-01 35.60 40 50 1.28 E-02 9.57 E-03 7.65 E-03 6.11 E-03 4.80 E-03 3.68 E-03 2.71 E-03 1.87 E-03 1.15 E-03 5.31 E-04 5.08 E-02 5.08E -03 3.05 E-01 59.93 60 75 9.15 E-03 6.82 E-03 5.41 E-03 4.28 E-03 3.34 E-03 2.54 E-03 1.86 E-03 1.28 E-03 7.84 E-04 3.61 E-04 3.58 E-02 3.58E -03 3.05 E-01 84.98 70 87.5 7.99 E-03 5.96 E-03 4.72 E-03 3.72 E-03 2.90 E-03 2.20 E-03 1.61 E-03 1.11 E-03 6.77 E-04 3.12 E-04 3.12 E-02 3.12E -03 3.05 E-01 97.61 1500 80 100 7.09 E-03 5.28 E-03 4.18 E-03 3.29 E-03 2.56 E-03 1.94 E-03 1.42 E-03 9.75 E-04 5.97 E-04 2.74 E-04 2.76 E-02 2.76E -03 3.05 E-01 110.28 2000 10 12.5 1.90 E-02 1.60 E-02 1.43 E-02 1.26 E-02 1.08 E-02 8.84 E-03 6.90 E-03 5.02 E-03 3.22 E-03 1.55 E-03 9.83 E-02 9.83E -03 2.70 E-01 27.43 20 25 1.56 E-02 1.20 E-02 9.97 E-03 8.26 E-03 6.71 E-03 5.28 E-03 3.98 E-03 2.80 E-03 1.75 E-03 8.17 E-04 6.72 E-02 6.72E -03 2.70 E-01 40.13 40 50 1.00 E-02 7.51 E-03 6.01 E-03 4.79 E-03 3.77 E-03 2.88 E-03 2.12 E-03 1.47 E-03 9.03 E-04 4.17 E-04 3.99 E-02 3.99E -03 2.70 E-01 67.58 60 75 7.18 E-03 5.35 E-03 4.25 E-03 3.36 E-03 2.62 E-03 1.99 E-03 1.46 E-03 1.00 E-03 6.15 E-04 2.83 E-04 2.81 E-02 2.81E -03 2.70 E-01 95.86 70 87.5 6.27 E-03 4.67 E-03 3.70 E-03 2.92 E-03 2.27 E-03 1.73 E-03 1.26 E-03 8.68 E-04 5.32 E-04 2.45 E-04 2.45 E-02 2.45E -03 2.70 E-01 110.12 80 100 5.56 E-03 4.14 E-03 3.28 E-03 2.58 E-03 2.01 E-03 1.52 E-03 1.11 E-03 7.65 E-04 4.68 E-04 2.15 E-04 2.17 E-02 2.17E -03 2.70 E-01 124.43

PAGE 142

124Table B-10. Velocity of plug with variation in shell thickness in case of loose sand. t* PL %PL* Velocity at Node* Tota l* Avg Max Ratio* 551 552 553 554 555 556 557 558 559 560 53 66.25 1.25E02 9.13 E-03 7.12 E-03 5.56 E-03 4.28 E-03 3.22 E-03 2.34 E-03 1.60 E-03 9.71 E-04 4.44 E-04 4.72 E-02 4.72 E-03 3.35 E-01 71.05 10 52 65 1.27E02 9.28 E-03 7.25 E-03 5.66 E-03 4.36 E-03 3.28 E-03 2.38 E-03 1.63 E-03 9.89 E-04 4.53 E-04 4.80 E-02 4.80 E-03 3.35 E-01 69.84 8 68 85 1.27E02 9.26 E-03 7.22 E-03 5.63 E-03 4.33 E-03 3.25 E-03 2.36 E-03 1.61 E-03 9.79 E-04 4.48 E-04 4.78 E-02 4.78 E-03 3.35 E-01 70.11 6 80 100 1.37E02 9.97 E-03 7.77 E-03 6.06 E-03 4.66 E-03 3.51 E-03 2.54 E-03 1.73 E-03 1.06 E-03 4.83 E-04 5.14 E-02 5.14 E-03 3.35 E-01 65.13 Table B-11. Velocity of plug with variation in shell thickness in case of dense sand. t* PL %PL* Velocity at Node* Tota l* Avg* Max Ratio* 551 552 553 554 555 556 557 558 559 560 10 50 62.5 1.31E02 9.76 E-03 7.75 E-03 6.14 E-03 4.79 E-03 3.65 E-03 2.67 E-03 1.84 E-03 1.13 E-03 5.19 E-04 5.13 E-02 5.13E -03 3.54 E-01 69.01 51 63.75 1.29E02 9.60 E-03 7.62 E-03 6.03 E-03 4.70 E-03 3.58 E-03 2.62 E-03 1.80 E-03 1.11 E-03 5.09 E-04 5.05 E-02 5.05E -03 3.54 E-01 70.22 8 66 82.5 1.29E02 9.63 E-03 7.63 E-03 6.03 E-03 4.69 E-03 3.57 E-03 2.61 E-03 1.79 E-03 1.10 E-03 5.06 E-04 5.05 E-02 5.05E -03 3.54 E-01 70.18 6 80 100 1.35E02 1.00 E-02 7.96 E-03 6.28 E-03 4.89 E-03 3.71 E-03 2.72 E-03 1.87 E-03 1.14 E-03 5.26 E-04 5.26 E-02 5.26E -03 3.54 E-01 67.29

PAGE 143

125 Table B-12. Plug height with change in t and D value. t-D (inch) %PL, Loose Sand %PL, Dense Sand 10"-60" 72.5 70 8"-54" 85 82.5 8"-48" 76.25 73.75 6"-36" 77.5 75 Table B-13. Plug he ight with change in density. Unit Weight %PL, Loose Sand %PL, Dense Sand 80 pcf 88.75 86.25 100 pcf 85 82.5 120 pcf 81.25 78.75 Table B-14. Plug height with cha nge in rate of penetration. Rate %PL, Loose Sand %PL, Dense Sand .5inch/sec 85 82.5 .4inch/sec 80 77.5 .3inch/sec 73.5 71.25 Table B-15. Plug height with change in shear strength. Viscosity or %PL, Loose Sand %PL, Dense Sand X: 500 pa-sec or 27.5degree 100 100 1000 pa-sec or 30degree 85 82.5 1500 pa-sec or 32.5degree 71.25 68.75 2000 pa-sec or 35degree 62.5 60 Table B-16. Plug height with variation in wall thickness. t (inch) %PL, Loose Sand %PL, Dense Sand 10 65 63.75 8 85 82.5 6 100 100

PAGE 144

126 APPENDIX C LRFDFACTOR Table C-1. Measured Vs predicted pile capacities. Table C-2. Statistical analysis data. ri 1.3828 r 0.391199 COV 0.282904 Sn o Projec t MeasuredWith Tip ri Full C/s ri 1St. Georges Island Project1050803.92121.3060981146.3070.915985 2St. Georges Island Project28001208.4552.3170081604.1471.745476 3St. Georges Island Project25501081.6872.3574281499.8551.700164 4St. Georges Island Project1425834.07711.7084751237.0751.151911 5Chesapeake Bay Bridge LT-4700477.75251.465194770.94490.907977 6Chesapeake Bay Bridge LT-6460324.33921.418268399.2571.15214 7San Mateo Hayward Bridge775699.22661.108367729.46691.06242 8South Test-4650328.54031.978448553.28481.174802 9Woodrow Wilson Bridge14751185.9681.243711600.3580.921669 10Woodrow Wilson Bridge15001230.6461.2188721530.2730.980217 11Woodrow Wilson Bridge900781.81221.151172951.48580.945889 12Salinas River Bridge750517.45041.449414862.2170.869851 13Port Of Oakland 27NC625462.38911.351675544.56711.147701 14Port Of Oakland 17NC1512.5439.07661.167222592.09110.865576 15Port Of Oakland 10NC1450400.46781.123686598.5040.751875 16Port Of Oakland 31NC600532.43351.126901592.54841.012575 17I-880 Oakland Site 3C450382.81671.175497467.41350.962745 18I-880 Oakland Site 3H600506.92491.183607600.4370.999272 19Santa Clara River Bridge 13925947.67310.9760751205.5960.767256 20Santa Clara River Bridge 71070996.90271.0733241436.450.744892 21Berenda Slough Br 4800702.77311.138347798.97251.001286

PAGE 145

127Table C-3. LRFDfactors, for various T, and QD/QL ratios. t 2.00 2.25 2.50 2.75 3.00 2.00 2.25 2. 50 2.75 3.00 2.00 2.25 2.50 2.75 3.00 QD/QL 1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 r 1.38 1.38 1.38 1.38 1.38 1.38 1.38 1.38 1.38 1.38 1.38 1.38 1.38 1.38 1.38 COV 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.87 0.80 0.74 0.69 0.64 0.83 0.77 0. 71 0.66 0.61 0.81 0.75 0.69 0.64 0.59 FS 1.73 1.87 2.02 2.18 2.36 1.71 1.85 2. 00 2.16 2.34 1.70 1.84 1.99 2.15 2.32 Table C-3 (continued). factors, for various T, and QD/QL ratios. t 2.00 2.25 2.50 2.75 3.00 2.00 2.25 2. 50 2.75 3.00 2.00 2.25 2.50 2.75 3.00 QD/QL 4 4 4 4 4 5 5 5 5 5 6 6 6 6 6 r 1.38 1.38 1.38 1.38 1.38 1.38 1.38 1. 38 1.38 1.38 1.38 1.38 1.38 1.38 1.38 COV 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.80 0.74 0.68 0.63 0.58 0.79 0.73 0. 67 0.62 0.58 0.78 0.72 0.67 0.62 0.57 FS 1.70 1.83 1.98 2.14 2.32 1.69 1.83 1. 98 2.14 2.31 1.69 1.83 1.97 2.13 2.31 Table C-3 (continued). factors, for various T, and QD/QL ratios. t 2.00 2.25 2.50 2.75 3.00 QD/QL 7 7 7 7 7 r 1.38 1.38 1.38 1.38 1.38 COV 0.28 0.28 0.28 0.28 0.28 0.78 0.72 0.67 0.62 0.57 FS 1.69 1.82 1.97 2.13 2.30

PAGE 146

128 LIST OF REFERENCES American Association of State Highway Tr ansportation Officials, 1996/2000. Load and Resistance Factor Design Bridge De sign Specification, 2nd Edition-2000 Interim Revisions. Washington, DC, pp. 28-33. Azzouz, A. S., Baligh, M. M., and Whittle, A.J, 1989. “Shaft Resistance of Piles in Clay.” J.Geotech. Engrg., AS CE, Vol. 116(2), pp. 205-221. Brucy, F., Meunier, J., Nauroy, J. F. 1991,“B ehavior of Pile Plug in Sandy Soils During and After Driving.” Paper Presented at the 23rd Annual Offshore Technology Conference, Texas, May 6-9, pp. 35-45. Chow, Y.K. 1981. “Dynamic Behavior of Piles. ” Ph.D. Thesis, University of Manchester. Davisson. M. T. 1972, “High Capacity Piles.” Proceedings, Soil Mechanics Lecture Series on Innovations in F oundation Construction. Amer ican Society of Civil Engineers, Illinois Sectio n, Chicago, pp. 81-112. DeBeer, E. 1970. “Proefondervinde Iijk e Bijdrage Tot de Studie Van Het Grandsdraagvermogen Van Zand Onder Funde ringer op Staal.” English version, Geotechnique, 20, Vol. 4, pp. 387-411. Kishida, H., and N. Isemoto. 1977. “Behav ior of Sand Plugs in Open-end Steel Pipe Piles.” Proc. 9th Int. Conf. on Soil Mech anics and Foundation E ngineering, Vol.1, pp. 601-604. Kyuho, P., Salgado, R. 2003,”Determination of Bearing Capacity of Open-Ended Piles in Sand.” Journal of Geotechnical and Ge oenvironmental Engineering, Jan 2003, Vol.23, pp. 24-27. Madabhushi, S.P.G., Haig, S.K. 1995, “Finit e Element Analysis of Pile Foundation Subjected to Pull out.” American Society of Civil Engineers, Illinois Section, Chicago, pp. 102-142. Paik, K.H., Lee, S.R. 1993,“Behavior of So il Plugs in Open Ended Model Piles Driven into Sands.” Marine Georesources an d Geotechnology, Vol. 11, pp. 353-373. Paikowsky, S.G. 1990,“The Mechanism of Pile Plugging in Sand.” Paper Presented at the 22nd Annual Offshore Technology Conference in Houston, Texas, May 7-10, pp. 23-45.

PAGE 147

129 Paikowsky, S.G., Whitman, R.V. 1990,“The Effects of Plugging on Pile Performance and Design.” Canadian Geotechnical Journal, Vol. 27, pp. 429-440. Paikowsky, S.G., Whitman, R. V., Baligh, M. M. 1990,“A New Look at the Phenomenon of Offshore Pile Plugging.” Marine Geotechnology, Vol. 8, pp. 213-230. Singletary, W. A. 1997, “Calibration of Load and Resistance Fact or Design Resistance Factors for Geotechnical Design in the State of Florida.” M.S Thesis, University of Florida. Smith, I. M., Wilson, S. M. 1986, “Plugging of Pipe Piles.” Proceedings of the 3rd International Confrence on Numerical Me thods in Offshore Piling, May 21-22, 1986, Vol. 24, pp. 34-37. Stevens, R.F. 1988,“The Effect of Soil Plug on Pile Drivability in Clay.” Application of Stress-Wave theory to Piles, Third Inte rnational Conference, May 25-27, Vol. 27, pp. 25-35. Vipulanandan, C., D. Wong, M. Ochoa, and M. W. O’Niell. 1989. “Modeling Displacement Piles in Sand Using a Pre ssure Chamber.”Foundation Eng. Current Principles Pract. ASCE Vol. 1, pp. 526-541. Withiam, J., Voytko, E., Barker, R., Duncan M., Kelly, B., Musser, S., and Elias, V. 1997. “Load and Resistance Factor De sign (LRFD) of Highway Bridge Substructures.” FHWA Publication no. HI-98-032, July, Washington, D.C.

PAGE 148

130 BIOGRAPHICAL SKETCH Dhuruva Badri was born September 20, 1980, in the city of Pune, in the Deccan region of India. As a child he had the opportu nity of being all over India, owing to the nature of his father’s work. He received his Bachelor of Engineering with distinction, from the National Institute of Technology, Karnataka, on May 2001. He then moved to Gainesville, Florida, for pursuing a Master of Science, specializ ing in geotechnical engineering at the Department of Civil and Coastal Engineering, University of Florida. In the fall of 2003, he will move to Miami, Florid a, and begin his career in the profession of civil engineering.


Permanent Link: http://ufdc.ufl.edu/UFE0001449/00001

Material Information

Title: Determination of Axial Pile Capacity of Prestressed Concrete Cylinder Piles
Physical Description: Mixed Material
Copyright Date: 2008

Record Information

Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UFE0001449:00001

Permanent Link: http://ufdc.ufl.edu/UFE0001449/00001

Material Information

Title: Determination of Axial Pile Capacity of Prestressed Concrete Cylinder Piles
Physical Description: Mixed Material
Copyright Date: 2008

Record Information

Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UFE0001449:00001


This item has the following downloads:


Full Text












DETERMINATION OF AXIAL PILE CAPACITY OF PRESTRESSED CONCRETE
CYLINDER PILES


















By

DHURUVA BADRI


A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA


2003

































Copyright 2003

by

Dhuruva Badri


































To Mom and Dad.















ACKNOWLEDGMENTS

I am indebted, first and foremost, to Dr. Michael McVay for providing me with an

opportunity to attend graduate school at the University of Florida. His guidance through

out the research project, along with his knowledge and approach to problem solving has

been a great plus.

I would like to thank Dr. Frank Townsend, for making graduate school a

pleasurable experience. His way of teaching classes, and always being there to help a

student with his problems will always be remembered.

I would also like to thank Mr. Peter Lai with the Florida Department of

Transportation (FDOT), for supporting the project and taking active interest in it.

I would like to thank the following people for supplying me with valuable load test

data, which were the heart of this project: Mr. Tom Shantz with Caltrans, Mr. Kurt

Krhounek with URS, Corp, Mr. Bill Spence with Tidewater Construction Corporation

(TCC), Mr. Brian Liebich with Caltrans, Mr. Mulla Mohammed with North Carolina

Department of Transportation (NCDOT), Mr. Jamey Batts with NCDOT, Mr. Ashton

Lawler, with Virginia Department of Transportation (VDOT).

I would like to express my deepest thanks to my Mother, my Father, my elder

sister, Divya, my brother in law, Madhav, my niece, Maya, and Parimala for their love,

support, understanding, and Reiki that kept me going through thick and thin.









I would like to thank Mr. Hugo Soto, Mr. John Pulsifer, Mr. Juan Villegas, and Miss.

Amy Guisinger and Ed Miguens with PSI, USA, for guiding me into a bright career after

graduate school.

Last, but certainly not least, I would like to express many thanks to my friends:

Amit, for helping me create the UF/FDOT Database; my room mates, Sajan, Devraj and

Vivek for their cooperation; Geotechs Minh, Arvind, Lila, Dinh, Hu, Evelio, Erkan,

Thai, Sangho, Sam, Mark; and friends Jason, Sid, Archit, Sridhar, Navin, Brandy,

Jayashree, and Sandeep for making my stay in Gainesville a pleasurable one.
















TABLE OF CONTENTS
Page

A C K N O W L E D G M E N T S ................................................................................................. iv

LIST OF TABLES ............. .................................. ........ ... .... .............

LIST OF FIGURES .............................................. ........ ...... ............. xiii

ABSTRACT .............. ..................... .......... .............. xvii

CHAPTER

1 IN TR OD U CTION ............................................... .. ......................... ..

1.1 Problem or Need Statem ent ................................................... ..... .......... 1
1.2 Scope of the Research ...................................... .... .. ...... .. .. .............. ..
1.3 Tasks Involved in the Project ................................................... .................. 1


2 DATA COLLECTION ........................................................... .. ............... 3

2.1 Classification of Load Test D ata ...................................... ................. ... ........... 3
2.1.1 Classification B ased on Soil Type.................................... .....................3
2.1.2 Classification Based on Pile M aterial................................... ...................4
2.1.3 Classification Based on Pile Outer Diameter and Shell Thickness............4
2.1.4 Classification Based on Plug Status ..................... .. ...... ....................5
2.2 Current UF/FDOT Cylinder Pile Database Projects, and Brief Description ..........5
2.2.1 St. Georges Island Bridge Replacement Project ................ ..................5
2.2.2 Chesapeake Bay Bridge and Tunnel Project .................. ...................
2.2.3 San-M ateo H ayward Bridge ....................................... .............. 8
2.2.4 Bridge over Oregon Inlet and Approaches on NC-12................................9
2.2.5 W oodrow W ilson Bridge.................... ................... ................... 10
2.2.6 Monitor-Merrimac Memorial Bridge-Tunnel (1-664 Bridge) ..................11
2.2.7 Salinas R iver B ridge.................................................... ................... 11
2.2.8 Port of O akland ....................................... ............ .. .. ............ 12
2.2.9 1-880 O akland Site.. ................................................ ........ .. .......... 12
2.2.10 Santa Clara River Bridge..................................................... ............... 13
2.2.11 B erenda Slough B ridge....................................... .......................... 14












3 UF/FDOT ONLINE CYLINDER PILE DATABASE.............................................15

3 .1 M a in P a g e ................. ................................................. ................ 1 5
3 .1.1 A dm inistrator U ser .......................................................................... .... 16
3 .1.2 R eg u lar U ser .............................................................. ............ .... 16
3.2 Project Page ............... ..... .... ........ ...... .. .. .............. ........... 17
3 .2 .1 G general P age .................................................................18
3.2.1.1 Project overview ......................................... .......................... 18
3.2.1.2 Pile description ......................................... ........ .... .. ............ 18
3.2.1.3 Insitu test and analysis................................ ........................ 18
3.2.2 Load Test Page ........................................... .... ..... .. ........ .... 19
3.2.3 Insitu Test and Soil Page ........................................ ........................ 21
3.2.4 Soil Plug Page.................. .... ....................... .. ......24
3.2.5 Driving Page .................. .......................... .... .... ................. 25
3.2.6 A analysis and R results Page................................... .................................... 26


4 D A T A R E D U C T IO N .................................................................... .... ...................27

4.1 Data Reduction Using Strain Gages ................................... ...............27
4.2 Data Reduction Using Davisson's and DeBeer's Method............................... 30
4.2.1 D avisson's M ethod..................................................... ... ............... 30
4.2.2 Back Computed Skin and End Bearing Values........................................31
4.3 Comparison Between Direct and Indirect Method ............................................33


5 ESTIM ATION OF SOIL PLU G ........................................ .......................... 36

5 .1 F orm ation of Soil P lu g ............................................................... .....................36
5.1.1 The A rching Phenom enon............................................... ....... ........ 37
5.1.2 Inertial Forces on the Soil Plug ..........................................................38
5.1.2.1 D during static loading .................................... ................................. 39
5.1.2.2 During driving ..................... ....................... .... .. 40
5.1.3 Parametric Study -Effects of Diameter, and G-Forces ............................40
5.2 ADINA Theory and Modeling........................... ............................. 43
5.2.1 General Overview of the Pile Model...................................................44
5.2.2 M material M odel of the Pile.................................................. ..................45
5.2.3 Properties of the Pile ............................................................................ 45
5.2.4 Pile Formulation ........................................... .................. ......... 45
5.3 AD IN A -F Theory and M odeling.................................... .................... .. .......... 46
5.3.1 General Overview of the Soil M odel............................... ............... 46
5.3.2 M material M odel of the Soil ........................................ ...... ............... 47
5.3.3 B oundary Condition ............................................................................47
5.3.4 Properties of the Soil Model ............... ............................................. 47
5.3.5 Soil F orm ulation .......... ........................................ ...... ...... .............. 48









5.4 ADINA-FSI Theory and M modeling ............................ ................................... 49
5.5 ADINA Plot ..................................................... ............... 50
5.6 Factors Affecting the Soil Plug............................ ...............51
5.6.1 Assumptions in Estimating the Soil Plug ............... ...............51
5.6.2 U nplugged Soil V elocity Profile ..................................... ............... ..54
5.6.3 Plugged Soil V elocity Profile.................................... ......... ............... 55
5.6.4 V aviation in Shell Thickness ........................................... ............... 56
5.6.5 Variation in the Outer Diameter of the Pile ....................... ............57
5.6.6 Variation in the Rate of Penetration of the Pile .............................58
5.6.7 V ariation in Shear Strength of Soil .................................... ............... 59
5.6.8 V ariation in U nit W eight of Soil ..................................... ............... ..60


6 SKIN FRICTION AND END BEARING CURVES ...........................................62

6.1 Unit Skin Friction and Unit End Bearing Curves....................... ............... 62
6.2 Comparison of Skin Friction and End Bearing with SPT2000...........................66
6.2 Comparison of Skin Friction and End Bearing with SPT2000...........................67


7 LOAD AND RESISTANCE FATOR DESIGN (LRFD)................ ..................76

7 .1 A llow able Stress D esign ............................................................ .....................77
7.2 Load R resistance Factor D esign ........................................ ........................ 77
7.3 Calibration of Resistance factor for LRFD........... ..... .................79
7.3.1 Engineering Judgment ............ ..... .............................. 79
7.3.2 Fitting A SD to LRFD ........................................ ........................... 79
7.3.3 R liability C alibration ........................................ .......................... 80
7.3.3.1 Resistance bias factor .................................. ...............80
7.3.3.2 R liability index P ..................................... ..................... .......... 81
7 .3 .3 .3 R resistance factor ............................................... .....................83
7 .4 C capacity P reduction ...................................................................... ...................84


8 RESULTS AND CONCLUSION...................... ..... ........................... 88

8.1 Finite Element Modeling of Soil Plug ........................................................88
8.2 Evaluating Unit Skin and Tip Resistance .................................. .................89
8 .3 L R F D Stu dy ......... ................... ..................................... ...............................90
8.4 Recommendations................................. 90









APPENDIX

A DATA REDUCTION AND DATABASE ...................................... ............... 91

B ADINA ANALYSIS OF SOIL PLUG ...... .............. ............... 117

C L R F D F A C T O R .................................................................. ..........................126

L IST O F R E FE R E N C E S ....................................................................... .................... 128

BIOGRAPHICAL SKETCH ........................................................... ........130
















LIST OF TABLES


Table page

2-1 Soil type and description ............................................................................. ..... 4

2-2 Pile type classification .................. ............................. .. ...... .. ........ ....

2-3 Classification based on pile outer diameter and shell thickness. ..............................4

2-4 Plugged and unplugged piles in the database ........................................................5

2-5 Current Pile D database ......................................... ................ .. ...... ....

2-6 Soil type classification for side and tip for various projects. ............. ................7

4-1 Contribution of skin and end bearing in DeBeer's. .............................................33

4-2 Comparison between direct and indirect method ..................................................35

5-1 Fixed parameters in study, and values. ........................................ ............... 42

5-2 Critical g-force values with diameter. ........................................... ............... 43

5-3 Pile Properties and its variations ........................................ ......................... 45

5-4 Soil Properties and its V ariation........................................ ........................... 48

5-5 Values used for pile outer diameter parametric study............................................58

7-1 Relationship between probability of failure and reliability index for lognormal
distribution (Rosenblueth and Esteva, 1972). .................................. .................82

7-2 M measured vs. predicted capacity table.............. ............................. .... ............. 85

8-1 Inertia theory Vs finite element modeling (arrows indicating whether the plugs go
u p or dow n). ....................................................... ................. 89

8-2 Skin friction and tip resistance equations (in terms of uncorrected SPT blow
counts), developed using the piles in the UF/FDOT cylinder pile database...........90

A-1 Current Database entry and description. ...................................... ............... 91









A-3 Data used for concrete piles in sand ........................... ......... ................. 93

A-4 Data used for steel piles in sand. ........................................ .......................... 93

A -6 D ata used for steel piles in clay........................................ ............................ 93

A-7 D ata used for concrete piles in silt. ........................................ ....... ............... 94

A-8 Data used for the end bearing in sand. ........................................ ............... 94

A-9 Data used for end bearing in silt ..................................................94

A -10 D ata used for end bearing in clay ......... ......... .............................. ............... 94

B-l Symbols used in finite element parametric study..................................................117

B-2 Velocity of plug with variation in ratio of diameter to shell thickness for loose
sa n d .......................................................................... 1 1 8

B-3 Velocity of plug with variation in ratio of diameter to shell thickness in case of
dense sand. ................................................................ .. .... ......... 118

B-4 Velocity of plug with variation in rate of penetration of the pile for loose sand. ..119

B-5 Velocity of plug with variation in rate of penetration of the pile for dense sand... 119

B-6 Velocity of plug with variation in density of soil for loose sand. ..........................120

B-7 Velocity of plug with variation in density of soil for dense sand........................120

B-8 Velocity of plug with variation of shear strength in case of loose sand...............121

B-9 Velocity of plug with variation in shear strength in case of dense sand ..............122

B-10 Velocity of plug with variation in shell thickness in case of loose sand ..............124

B-11 Velocity of plug with variation in shell thickness in case of dense sand.............124

B-12 Plug height with change in t and D value........... ...................... ..........125

B-13 Plug height with change in density. ............................................ ............... 125

B-14 Plug height with change in rate of penetration.............................. ................125

B-15 Plug height with change in shear strength.......................................................... 125

B-16 Plug height with variation in wall thickness. ................................. ............... 125

C-1 M measured Vs predicted pile capacities. ........................................ ...............126









C -2 Statistical analy sis data............................................................................ .... ... 126

C-3 LRFD-4 factors, for various PT, and QD/QL ratios........................... ...............127
















LIST OF FIGURES


Figure pge

3-1 Shows the MAIN page with the username and password fields, and a note to new
u se rs ...............................................................................................1 5

3-2 Shows the MENU page, with the enter data and view data fields .........................16

3-3 PROJECT page showing a list of projects available on the UF/FDOT online
database. ................................................................... 17

3-4 Shows the format of the General page. ................................. ..............19

3-5 Shows the format of the Load test page. ................... .............................. 20

3-6 Shows a plot of load displacement of the pile.................................. ... ..................20

3-7 Shows a screen shot of the strain data page. .................................... .................... 21

3-9 Plot of Cone resistance V s elevation ............................................. ............... 22

3-10 Screen shot showing the format for the SPT page. ...............................................23

3-11 Plot of blow count Vs elevation. ................ ........... .......... ............... 24

3-12 Description of the parameters used in defining the soil plug.................................24

3-13 Screen shot of the soil plug page.........................................................25

3-14 Screen shot of the driving page. ........................... ............... 25

3-15 Screen shot of the analysis and results page. ................................... ... ..................26

4-1 A plot of load distribution along the pile Vs strain gage elevation with increment
in axial load/ time for the St. Georges Island Bridge Replacement project.............29

4-2 Determining capacity of pile, using Davisson's method, for the St. Georges
Island Bridge Replacement Project, Load Test- ................................ ...............31

4-3 Separation of load vs. deformation plot into skin and tip. .....................................32

4-4 Separating skin friction and end bearing using DeBeer's method...........................32









4-5 Interpretation of Pile load test. (High Capacity Piles, M.T Davisson)...................34

5-1 Isobars of the vertical stress with in the soil plug, showing the transition from
active to passive arching. ............................................... .............................. 37

5-2 Free body diagram of soil column with in the pile during, A) Static loading, and
B ) Pile D driving. .......................................................................38

5-3 Screen shot of the MathCAD file showing plug height, upward force, and
downward force calculations...................... ...... ............................. 41

5-4 Variation of plug height with soil plug diameter and g-forces.............................42

5-5 Isoparametric Nine Node Axisymmetric Element .................................................44

5-6 ADINA pile input, thick lines indicating contact surface .....................................46

5-7 Figure showing the slip and no slip surfaces along the various boundaries ............47

5-8 Showing an ADINA-F soil m esh ........................................ ......................... 48

5-9 C contact Surface G eom etry. ........................................................... .....................50

5-10 ADINA Plots ....................... ......... ... .......... ............... 50

5-11 Flow chart indicating the various steps in the analysis of the plug..........................51

5-12 Velocity profile with in the finite element model. ................................................52

5-13 Plot showing variation in velocity with in the pile with change in plug height.......54

5-14 Velocity profile with in cylinder pile- unplugged condition.............................. 55

5-15 Velocity profile with in cylinder pile- plugged condition............... .......... 56

5-16 Plot showing variation of shell thickness with height of soil plug.........................57

5-17 Plot showing variation in the soil plug with change in outer diameter .................58

5-18 Variation in Rate of Penetration................................... ................. 59

5-20 V ariation in U nit W eight of Soil ................................................... .....................61

6-1 Skin friction (tsf) Vs N (uncorrected) for concrete piles in sand ...........................63

6-2 Skin friction (tsf) Vs N (uncorrected) for steel piles in sand. ................................63

6-3 Skin friction (tsf) Vs N (uncorrected) for concrete piles in clay............................64









6-4 Skin friction (tsf) Vs N (uncorrected) for steel piles in clay..................................64

6-5 Skin friction (tsf) Vs N (uncorrected) for concrete piles in silts............................65

6-6 End bearing (tsf) Vs N (uncorrected) in Sands ....................................................... 65

6-7 End bearing (tsf) Vs N (uncorrected) in Clays...................................................66

6-8 End bearing (tsf) Vs N (uncorrected) for silts ......................................................66

6-9 Comparison of various designs used for computing unit skin friction in clays.......68

6-10 Comparison of various designs used for computing unit skin friction in silts.........69

6-11 Comparison of various designs used for computing unit skin friction in sands. .....70

6-12 Comparison of various designs used for computing unit end bearing in clays........71

6-13 Comparison of various designs used for computing unit end bearing in silts..........72

6-14 Comparison of various designs used for computing unit end bearing in sands. ......73

6-15 Comparison of unit skin friction vs. SPT N values, for various soil types, and
pile materials, in case of cylinder piles. ...................................... ............... 74

6-16 Comparison of unit end bearing vs. SPT N values, for various soils, in case of
cy lin der piles. ...................................................... ................. 7 5

7-1 Failure region and the reliability ....................................... ........................ 82

7-2 Resistance Factor vs. Dead to Live Load Ratio, Large Diameter Cylinder Pile
w ith ring area............................................................................................. 86

7-3 Resistance Factor vs. Dead to Live Load Ratio, Large Diameter Cylinder Pile
w ith ring area........................................................................ ... ...... ...... 86

7-4 Comparison of measured vs. predicted capacities. ................................................87

A-i St. Georges Island Bridge Replacement Project LT-1 ......................... ..........95

A-2 St. Georges Island Bridge Replacement Project, LT-4........................................96

A -3 Chesapeake B ay L T-1 ............................................. .....................................97

A -4 C hesapeake B ay L T-2. ..................................................................... ..................98

A -5 C hesapeake B ay L T-6. ..................................................................... ..................99

A-6 San M ateo Hayward Bridge-A. ........................................ .......................... 100









A -7 1-664 Bridge Test-4. ...... ........................... ........................................... 101

A -8 1-664 Bridge Test-7. ...... ........................... ........................................... 102

A-9 W oodrow W ilson Bridge-C. .............................................................................103

A-10 Woodrow Wilson Bridge-F ........... .. ...... ......... ............... 104

A -11 W oodrow W ilson B ridge-I .............................. ........................ ............... 105

A-12 Oregon Inlet .............. .................................... ........... 106

A -13 Salinas R iv er B ridge....................................................................... ..................107

A-14 Port of Oakland Bridge 27N C ....................................................... ............. 108

A-15 Port of Oakland Bridge 10N C ................................................................... 109

A-16 Port of Oakland Bridge 17N C ................................................... ..................110

A -17 Port of O akland Bridge 31N C ....................................................... .............. ..

A-18 1-880 Bridge 3H. .......... ............................................ 112

A-19 1-880 Bridge 3C ........... ................................... .... ...... ........... 113

A-20 Santa Clara River Bridge Pier-7 ........................................................ ............... 114

A-21 Santa Clara River Bridge Pier-13. ........................... ..... ...............15

A-22 Santa Clara River Bridge Pier-13. .............................. ..................116















Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science

DETERMINATION OF AXIAL PILE CAPACITY OF PRESTRESSED CONCRETE
CYLINDER PILES


By

Dhuruva Badri

December 2003

Chair: Michael McVay.
Major Department: Civil and Coastal Engineering.

Recognizing the numerous advantages of large diameter cylinder piles, the Florida

Department of Transportation (FDOT) and its contractors have been considering their use

in place of smaller diameter piles, and drilled shafts. Thirty-six load test data on large

diameter cylinder piles were collected nationwide. The data were then separated based on

soil type, pile material (concrete/steel), pile geometry (shell thickness/ outer diameter),

and the state of plug (plugged/unplugged), and then placed into the UF/ FDOT cylinder

pile database.

These load test data were then reduced into unit skin friction, and unit end bearing

vs. SPT N values, for different soil types, and pile material. These results would be used

in updating the axial pile capacity assessment software, S.P.T 97. Further, an LRFD (i.e.,

Load Resistance and Factor Design) study was performed in order to check the reliability

of the design.









During pile installation, soil enters the annular region of the pile tip forming a

column of soil. The length of this column has to be estimated in the drivability analysis,

and the state of plug has to be determined for calculating the end bearing. The pile

installation process was modeled using the finite element, and a parametric study was

performed to study the factors impacting the formation of the soil plug.


xviii














CHAPTER 1
INTRODUCTION

The research project consists of determining the axial pile capacity of prestressed

concrete cylinder piles, for the Florida Department of Transportation (FDOT).

1.1 Problem or Need Statement

The research was performed considering the numerous advantages of using a large

diameter cylinder pile as compared to several smaller piles, or drilled shafts. For instance,

the large diameter cylinder pile has a larger moment of inertia as compared to a smaller

diameter pile, and will resist large lateral loads (i.e., ship impacts). Also, the cylinder pile

will provide larger skin and tip resistance in sands, and clays, as compared to a similar

size drilled shaft (i.e., similar moment of inertia), due to its method of installation. In

addition, the results of the research would be used to update the axial pile capacity

assessment software, SPT97, to include prestressed concrete cylinder piles.

1.2 Scope of the Research

The scope of this research involved the engineering knowledge of deep foundation

analysis and design, databases, F.E.M (i.e., Finite Element Method) theory, and

application software ADINA (i.e., Automatic Dynamic Incremental Non-Linear

Analysis).

1.3 Tasks Involved in the Project

The various tasks involved were as follows:

1. Collecting cylinder pile load test data: In order to collect cylinder pile load test
data, over eighty Geotechnical companies, and Federal Agencies, were contacted
nation-wide, and around the world. A total of thirty-six, load test data on large









diameter cylinder piles were collected. A list of companies contacted, and data
obtained are provided in the forthcoming chapters.

2. Developing a database based on pile dimension, and soil type: The data in the
database was separated based on the soil type, pile material, outer diameter of the
pile, shell thickness of the pile, and the state of plug within the pile (i.e.,
plugged/unplugged). An online database was then built to store and share data with
other researchers. The knowledge of Microsoft Access, ASP (i.e., Active Server
Protocol), SQL (i.e., Structured Query Language) and JavaScript was used in the
design of this database.

3. Evaluating Unit Skin and Tip Resistance: The results of the load test were reduced
into unit skin friction, and unit tip resistance, using data from strain gages, and a
combination of Davisson's method, and deBeer's method. These results were then
correlated against uncorrected SPT blow counts (N), for different soil types and
pile material. The results of this test were then compared with the present design,
used in SPT97.

4. Determination of Soil Plug heights, what impacts it and its effects on soil capacity:
The effect of inertia of the soil plug on its height was studied. The knowledge of
F.E.M (i.e., Finite Element Method), and application software ADINA (i.e.,
Automatic Dynamic Incremental Non-Linear Analysis) was used in modeling the
soil plug response. A parametric study was then carried out to determine the factors
impacting it and their extents.

5. Evaluating bias (i.e., measured over predicted), COV (i.e., coefficient of standard
deviation) and determining the LRFD 4 (i.e., Load Resistance and factor design).















CHAPTER 2
DATA COLLECTION

In order to collect static load test data on large diameter cylinder pile over eighty

geotechnical companies, and federal agencies were contacted nation wide and around the

world.

All projects were undertaken on behalf of federal Agencies like, Florida

Department of Transportation (FDOT), California Department of Transportation

(CALTRANS), Virginia Department of Transportation (VDOT), North Carolina

Department of Transportation (NCDOT) and Maryland State Highway Administration

(MSHA).

All Static Axial Load Testing procedures were in general conformance with ASTM

D 1143-81 (1994).

2.1 Classification of Load Test Data

The data from the load test were placed in the database, and then classified based

on:

1. Soil type.
2. Material of the Pile.
3. Outer diameter, and shell thickness of the pile.
4. State of the soil plug.


2.1.1 Classification Based on Soil Type

Based on the SPT97 program, the soil was classified into four types. Table 2-1 lists

the soil types, and a brief description.










Table 2-1. Soil type and description
Soil Type Description Number

1 Plastic Clay 13

2 Clay-silt-sand mixtures, very silty sand, silts and 11
marls
3 Clean Sands 18

4 Soft Limestone, very shelly sands 2



2.1.2 Classification Based on Pile Material

Based on the material of the pile, the piles were classified into concrete, and steel

piles. Table 2-2, lists the number of piles of each type, in the database.

Table 2-2. Pile type classification.
Material Type Description Number
1 Concrete 27
2 Steel 9



2.1.3 Classification Based on Pile Outer Diameter and Shell Thickness

Piles were classified based on their outer diameter, and shell thickness, to evaluate

the effect of geometry on unit skin friction, unit end bearing, and the formation of soil

plug. Table 2-3, lists the number of piles of various diameters, and shell thickness.

Table 2-3. Classification based on pile outer diameter and shell thickness.
Outer Diameter Number Shell Thickness Number
84-inch 1 8-inch 4
72-inch 2 6.9-inch 2
66-inch 3 6-inch 7
54-inch 19 5-inch 10
42-inch 10 2-inch to 1-inch 5
36-inch 1 >1-inch 8









2.1.4 Classification Based on Plug Status

Based on the type of plug, the piles were classified as plugged piles, and unplugged

piles. A plugged pile was defined as one in which, the soil within the pile had no relative

movement with respect to the pile. All other piles were defined as unplugged piles. Table

2-4, lists the number of plugged piles, and unplugged piles in the database.

Table 2-4. Plugged and unplugged piles in the database.
Plug Status Number
Plugged 11
Unplugged 25


2.2 Current UF/FDOT Cylinder Pile Database Projects, and Brief Description

Table 2-5 lists thirty-six piles, from eleven different projects, in the current

UF/FDOT database, along with a brief description of the outer diameter, shell thickness,

pile material, major soil type, and the number of tests data available from this project. A

brief description of each follows.

2.2.1 St. Georges Island Bridge Replacement Project

The Bridge was built for the Florida Department of Transportation (FDOT) by the

team of Boh Brothers Construction, and Jacob Civil, Inc; in Apalachicola Bay over inter

coastal waters. Applied Foundation Testing, Inc performed the load test. The piles tested

were spuncast post tensioned concrete cylinder piles with an outer diameter of 54-inches,

shell thickness of 8-inches and lengths of 80-ft.

The prevailing soil type at the location was very loose silty sand, above a layer of

dense to very dense silty sand, underlain by a layer of limestone. The piles were driven to

refusal in the limestone layer. Additional details on the soils, pile, and installation were

available from the geotechnical records of Williams Earth Sciences, Inc. (WES). Insitu









data from both CPT (i.e., Cone Penetration Test) and SPT (i.e., Standard Penetration

Test) are available for this particular project.

Table 2-5. Current Pile Database
Project Name Pile Description Major Soil Number
Outer Shell Pile Type of Tests
Diameter Thickness Material

1 St. Georges Island 54-inch 8-inch Post Silty Sands 4
Bridge Replacement Tensioned over
Project, FL Concrete Limestone
2 Chesapeake Bay 54-inch, 6-inch Prestressed Dense 6
Bridge and Tunnel 66-inch Concrete sands
Project, VA
3 San-Mateo Hayward 42-inch 6.9-inch Concrete Silty Clays 2
Bridge, CA

4 Oregon Inlet, NC 66-inch 6-inch Concrete Silty Fine 1
Sands
5 Woodrow-Wilson 54-inch, 1-inch Steel Silty Sands 3
Bridge, MD 42-inch
and 36-
inch
6 North and South 54-inch 5-inch Concrete Silts and 10
Trestle, 1-664 Bridge, Sands
VA
7 Salinas River Bridge, 72-inch .75-inch Steel Mixed 1
CA
8 Port of Oakland, CA 42-inch .625-inch, Steel Clays 4
.75-inch
9 1-880 Oakland, CA 42-inch .75-inch Steel Clays 2
10 Santa Clara River 84-inch, 1.5-inch, Steel Sands 2
Bridge, CA 72-inch 1.74-inch

11 Berenda Slough Br, 42-inch .625-inch Steel Sands 1
CA
Total 36


Also, the soil at the side and tip were identified for correlation purpose (Chapter-4,

and Chapter-6), from the logs of SPT boring data as shown in table 2-6.









Table 2-6. Soil type classification for side and tip for various projects.
Soil Type For
Sno Project Name Soil Type For Insitu Test
Skin Friction End Bearing
1 St. Georges Island Project Sand Limestone SPT/CPT
2 St. Georges Island Project Sand Limestone SPT/CPT
3 St. Georges Island Project Sand Limestone SPT/CPT
4 St. Georges Island Project Sand Limestone SPT/CPT
5 Chesapeake Bay Bridge Silt Silt CPT/SPT
6 Chesapeake Bay Bridge Silt Silt CPT/SPT
7 Chesapeake Bay Bridge Silt Silt CPT/SPT
8 Chesapeake Bay Bridge Sand Sand CPT/SPT
9 Chesapeake Bay Bridge Sand Sand CPT/SPT
10 Chesapeake Bay Bridge Sand Sand SPT
11 San Mateo Hayward Bridge Silt Silt SPT
12 San Mateo Hayward Bridge Silt Silt SPT
13 Oregon Inlet Silt Silt CPT/SPT
14 1-664 Bridge North Clay Clay SPT
15 South Test-4 Sands Sands SPT
16 South Test-5 Sands Sands SPT
17 South Test-6 Sands Sands SPT
18 South Test-10 Sands Sands SPT
19 South Test-11 Sands Sands SPT
20 South Test-12 Sands Sands SPT
21 South Test-13 Sands Sands SPT
22 South Test-14 Sands Sands SPT
23 Woodrow Wilson Bridge Sands Clays SPT
24 Woodrow Wilson Bridge Sands Clays SPT
25 Woodrow Wilson Bridge Sands Clays SPT
26 Salinas River Bridge Clays Clays SPT
27 Port Of Oakland 27NC Clay Clays SPT
28 Port Of Oakland 17NC1 Clay Clays SPT
29 Port Of Oakland 10NC1 Clay Clays SPT
30 Port Of Oakland 31NC Clay Clays SPT
31 1-880 Oakland Site 3C Clay Clays SPT
32 1-880 Oakland Site 3H Clay Clay SPT
33 Santa Clara River Bridge 13 Sand Sands SPT
34 Santa Clara River Bridge 7 Sand Sands SPT
35 Berenda Slough Br 4 Silts Silts SPT


Data for four compression load test were available from this project. Reaction

load was applied through frame-supported water filled barges. Four pipe piles supported









this weighted box apparatus. Loading rate was generally governed by filling the barges

with water. All test piles were instrumented with embedded strain gages and a toe

accelerometer. The piles at this project did not form a soil plug.

2.2.2 Chesapeake Bay Bridge and Tunnel Project

The load testing was performed as a part of building a parallel crossing to the

already existing Chesapeake Bay Bridge. The CBBTD (i.e., Chesapeake Bay Bridge and

Tunnel District) contracted with Tidewater Construction Corporation (TCC), to perform

the construction, installation, and loading of the test piles. Bayshore Concrete Products,

Inc., a subcontractor to TCC, fabricated the piles.

Load test information for six prestressed concrete cylinder piles is available from

this project. Fifty-four inch diameter piles were used at TP-1, TP-2, TP-3, and TP-6,

whereas 66-inch diameter piles were used at TP-4 and TP-5. All piles were 6-inch thick.

The lengths of these piles varied from 128-ft at site TP-6 to 204-ft at site TP-5.

The prevailing soil at location TP-1, TP-2 and TP-6 was silt and clay with small

amounts of sand; and at location TP-3, TP-4 and TP-5 the prevailing soil was dense gray

sand with small amounts of silt and clay. Insitu data from both SPT and CPT are

available for this project.

Piles TP-1, TP-4, TP-5 and TP-6 formed soil plugs, the upper surface of the plugs

formed in these piles were at depths of 13-ft, 1-ft, 8-ft, and 6-ft below mudline. Piles TP-

2 and TP-3 did not form any soil plug.

2.2.3 San-Mateo Hayward Bridge

The San Mateo Bridge, also called the San Mateo Hayward Bridge, runs roughly

east west so as to cross the lower part of San Francisco Bay. It carries California State

Highway 92 so as to join Haywood, 1-580 and 1-880 on the east side of the bay with









Foster City, San Mateo and US101 on the west side. The scope of the project involved

building a new 60-foot trestle on the north side of the already existing trestle.

CALTRANS performed load test on two large diameter prestressed concrete

cylinder piles. The piles had an outer diameter of 42-inch, and a shell thickness of 6.9-

inch. The length of the pile was 42.25-meters at site A, and 40.8-meters at site B.

SPT data are available for this project. The closest boring to Site A, indicates layers

of very soft silty clay down to an elevation of -55-feet, followed by interbedded layers of

compact silty clay, and compact sand down to the specified tip elevation of the pile. The

closest boring in the vicinity of Site B indicates very soft silty clay down to an elevation

of -20-feet, followed by interbedded layers of stiff silty clay, and compact sand down to

the specified tip elevation of the pile.

2.2.4 Bridge over Oregon Inlet and Approaches on NC-12

The bridge over Oregon Inlet and approaches on NC-12 is located on the south side

of Oregon Inlet's Bonner Bridge in Dare County, North Carolina.

The. North Carolina Department of Transportation (NCDOT) contracted with

Hardway Company, and S&ME Environmental Services for Pile and Test Boring

contracts.

The test consisted of Static Axial Compressive load test on a 66-inch diameter

concrete cylinder pile with a shell thickness of 6-inch, and a length of 131.5-feet.

Insitu data from both SPT, and CPT are available for this project. The soil profile

consists of clayey silt to a depth of -12-meters, and layers of sand and sandy silt till the

tip elevation.

The pile did not form a soil plug.









2.2.5 Woodrow Wilson Bridge

The Woodrow Wilson Bridge is located about 6 miles south of Washington DC

Metropolitan area; it is approximately at the mid point of 1-95, one of the busiest east

coast interstate highways.

The load testing for the project was planned and implemented by Potomac Crossing

Consultants (PCC), a joint venture of URS Corporation, Parsons-Brinkerhoff, and

Rummel-Klepper-Kahl, in the capacity of the General Engineering Consultant (GEC). All

work was authorized by the Maryland State Highway Administration (MSHA) in

conjunction with the Federal Highway Administration (FHWA) and was performed in

association with Section Design Consultant (SDC), Parson Transportation Group (PTG)

and Mueser Rutledge Consulting Engineers (MRCE).

Three axial static load tests are available from this project and are identified as

PL-1, PL-2 and PL-3. PL-1 was located near the eastern bascule pier in the main shipping

channel of the Potomac River, PL-2 was located to the west of the secondary channel

near the eastern abutment, and PL-3 was located on land in Jones Point Park, Virginia.

The site lies in the Atlantic Coastal Plain, which consists of a wide belt of

sedimentary deposits overlying the crystalline bedrock of the Piedmont, which outcrops

to the northwest. These materials, known collectively as the Potomac Group, consist of

dense sands and gravels with variable fractions of fines, and very stiff to hard, highly

overconsolidated clays. Although these clays are very hard, the presence of slickensides

often reduces the overall shear strength of the soil mass. These clays vary in mineral

composition, resulting in variable potential for expansion. Insitu data from SPT are

available for this project.









The Potomac River is a tidal river with a mean water elevation of +1 feet above

sea level, fluctuating between Mean Low Water of elevation -1-feet and Mean High

Water of elevation +3-feet.

The three steel piles at PL-1, PL-2, and PL-3 had outer diameters of 54-inch, 42-

inch, and 36-inch and, lengths of 164-ft, 125-ft, and 96-ft respectively. All piles had a

shell thickness of 1-inch. None of the piles formed a soil plug.

2.2.6 Monitor-Merrimac Memorial Bridge-Tunnel (1-664 Bridge)

The Monitor-Merrimac Memorial Bridge-Tunnel connects 1-664 in Hampton to I-

664/I-264 Chesapeake. The Virginia Department of Transportation (VDOT) contracted

with STS Consultants Ltd of Virginia for conducting the various load tests.

Static axial load test were performed on 54-inch diameter prestressed concrete

cylinder piles with a wall thickness of 5-inch and lengths varying from 47.9-ft at Test-4

to 145.1-ft at Test-10. A total often load test data is available from this project, one on

the north side and nine on the south side of the bridge.

The general soil profile at the site indicates interbedded layers of soft black silt,

very soft gray silty clay, green-gray sandy silts, and sandy clays. These soils comprise the

Yorktown formation, which exhibits a significant amount of soil freeze or setup. Insitu

data from SPT are available for this project.

None of the piles formed a soil plug.

2.2.7 Salinas River Bridge

The Salinas River Bridge is located on SR101, over the Salinas River near

Soledad, California. Data on one 72-inch diameter, .75-inch thick steel pipe pile is

available from this project. The pile was installed specifically for testing (and not to be









incorporated into the bridge structure) by the personnel from the Office of Structural

Foundation, Geotechnical Support Branch of Caltrans.

Boring B-13 is the closest boring to the test pile, located about 90 feet away.

Boring B-13 shows layers of loose to compact sand from the ground surface elevation of

7-ft to -32-ft. The sand layers are underlain by a layer of soft clay to an elevation -52-ft,

and layers of loose silt to an elevation -70 ft. Below these layers to an elevation of-103

ft are layers of soft to stiff clay. From elevation -103 ft to -121 ft is a layer of dense sand.

Insitu data from SPT are available for this project.

The pile did not form an internal soil plug during installation. Measurements

taken upon completion of driving showed the top of soil plug to be 13 feet below ground

surface elevation. The difference in elevation between the top of soil plug and original

ground elevation is likely a result of vibration-induced settlement of the soil inside the

pile, or result of the soft clay being displaced by the denser material inside the pile.

2.2.8 Port of Oakland

Four static axial load tests on 42-inch diameter, cast-in-steel shell concrete piles

were conducted at the Port of Oakland Connector Viaduct and Maritime On and Off

Ramps. Members of the Geotechnical Support Branch of Caltrans conducted these tests.

Subsurface conditions at the three sites can be estimated based upon fieldwork

completed by Caltrans. Soil encountered at all of the test locations consisted of three

distinct materials: fill, Young Bay Mud deposit, and Old Bay Mud deposits. Throughout

the jobsite the elevations separating these four materials varied considerably.

2.2.9 1-880 Oakland Site

The load test site is located at the west end of the West Grand Avenue aerial

structure, approximately 1100 feet east of the San Francisco Oakland Bay Bridge Toll









Plaza and north of the existing west bound lanes of 1-80, along the margin of the San

Francisco Bay. Caltrans carried out the test in an effort to better understand issues

associated with the use of large diameter steel piles. The study consisted of installing two

42-inch diameter and .75-inch thick steel cylinder piles.

Soils at these various test sites consists of Artificial Fill; Young Bay Mud an

unconsolidated Holocene estuarine deposit; Merritt Sands a Pleistocene non-marine

deposit (member of the San Antonio formation); and Old Bay Mud an older Pleistocene

marine deposit also referred to as Yerba Buena Mud. Depth to bedrock is estimated to

vary from -500 ft to -550 ft.

The piles at Site 3 were 120 ft in length. Due to transportation and handling

constraints, driving occurred in two phases. The first portion of pile installation consisted

of installing a nominal 80 ft long pile spliced together from two 40 ft section in a nearby

fabrication yard. The remaining 40 ft section of the pile was suspended vertically, then

welded to the portion of the pile previously installed. Piles were then driven to the

specified tip elevation.

At the completion of installation, the plug was measured at 3.25 ft below the

original ground in case of Pile 3C and 10 ft in case of Pile 3H.

2.2.10 Santa Clara River Bridge

The load test program was a part of the Santa Clara River Bridge replacement, on

the I-5 and I-5/SR-126 road separation (Magic Mountain Parkway) in Los Angeles

County at Santa Clarita. The project included the installation of two large diameter cast-

in-steel-shell (CISS) piles at location Pier 13 and Pier 7. The piles at Pier 13 and Pier 7

were 72-inch diameter, 1.5-inch thick and 84-inch diameter and 1.74-inch thick

respectively. Personnel from the Foundation Testing Branch (FTB), of the Office of









Geotechnical Support (Caltrans) conducted two compressive static axial load tests each at

Pier 13 and Pier 7.

The subsurface location at pier 13 as inferred from Boring B 1-99 indicates the

presence of alternating layers of very stiff clay and dense sand with silt and gravels. At

deeper depths, the boring encountered very dense layers of sands and gravels. The

subsurface location at Pier 7 location as inferred from Boring 00-3 indicates the presence

of alternating layers of medium to very dense silts and sands with very stiff clays. At

deeper depth, the boring encountered very dense layers of sands and gravels over

cemented silty sands. Insitu data from SPT are available for this project.

2.2.11 Berenda Slough Bridge

The Berenda Slough Bridge is located on Route 220 in Madera County near

Chowchilla. The project included the installation of 42-inch diameter, .625-inch thick

cast-in-steel-shell pile, by the personnel from the Foundation Testing and Instrumentation

Branch of the Division of Structural Foundations.

Boring 98-5 indicates layers of sand, silty sand, and silt present at the test pile

site. Insitu data from SPT are available for this project.

















CHAPTER 3
UF/FDOT ONLINE CYLINDER PILE DATABASE

The online UF/FDOT large diameter cylinder pile database was developed, as a


joint effort with researchers around the world on large diameter driven piles. The main

purpose of the database was to share the existing load test data, and get more data. The

database was built on a Microsoft Access, html (i.e., HyperText Markup Language), ASP

(i.e., Active Server Pages) and JavaScript platform.

3.1 Main Page

The MAIN page, grants the user permission to enter the database. Based on the


type of username and password, the user is identified as an administrator, or a regular

user, and given permission to access the various pages within the database.



OTA CIF -O
WDO ATABASE Im



Username
Password





Thank you for visiting the Florida Department of Transportations (FDOT) online
Large Diameter Cylinder Pile Database. This database was developed as a joint
effort with researchers around the world on driven cylinder piles. In order to
gain access to this database you will need to contact Mr. Peter Lai of the
Florida Department of Transportation by e-mail (peter.lai@dot.state.fl.us) or
call him at (850) 414-4306.
We would greatly appreciate more static load test and soil data for the
database. In case of any questions on navigating the website or the database
entries please feel free to contact the Webmaster.

III ., I i I r,- I


Figure 3-1. Shows the MAIN page with the username and password fields, and a note to
new users.









3.1.1 Administrator User

All users are given access from the MAIN page, into the MENU page. Once at the

MENU page, an administrator user is given access to both data entry, and viewing the

already existing data.


L ( DOTC DATABASE





SENT-ER DATA



VIEW DATA



Figure 3-2. Shows the MENU page, with the enter data and view data fields.

3.1.2 Regular User

A regular user has rights only to view the data (i.e., VIEW DATA page), and would

be prompted to enter the administrative username and password to enter the ENTER

DATA page.

Once the user enters the VIEW DATA page, he/she would be taken to the

PROJECTS page. The PROJECTS page, lists all the projects in the database, the user can

view the details of the listed project from there on.

The various pages within the ENTER DATA and VIEW DATA are discussed

simultaneously, as they have the same formats.










3.2 Project Page

The PROJECT page lists the names of all the projects in the database, in three

columns. The data for each project is presented in six sections (pages). An option of

navigating back to the list of projects (PROJECT page) is available from each of these

pages. The six pages describing each project are as follows:

1. General page.

2. Load test page.

3. Insitu test and soil page.

4. Soil plug page.

5. Driving page.

6. Analysis and results page.

A brief description of each page follows.



DOT C DATABASE -





,i:h [ i-I 4 Bridge Over Oregon Inet on NC Ba B LT-
2t r. : .I 'hIi --: ." "1:J".'' Bay Brid e LT-1
12
.L : 1 .' i l-I LT-I *.'l. i :.:d.- e :, I-i LT-. Chesapeake Bay Bridee LT-4
11.- il ,-, 1.1, i._. :T-: .- r--*h ,r,- E ,;E,, _-.. LT- 1_. Test-10. V A
T-'.-.4 .i i Te.'t-ll.VA I- -41 L i- T-,l. P 1:," TE-;.-? F.
-. 4 1..- T-.:r-14, VA _-J -Bri I, T. r--,VVA I-664 Brdge, Test-5 VA
1-,- ii +:-, l--1 ".. I-880 Oakland Site 3C I-880 Oakland Site 3I
I IT ': lJ2 1 Ir.1 1l I ii t d:11 1'J iJ I I t -d L iJ I IIT::
S IT .dJ.UJ.I Il Tl' ..dian.i: l-i ei J.II SantaClara River Bridge I 1 .
r II T r r i I- 1 I lE I lr St. eorges Island Ei 1
u r I u 1 J II j II I I, [ -T .
"I .1 .:i-:':ir,, [ Li 1 __': I._,:-,.i-,it L 1--
ri I'-, il i ii ,- .'r,_-,- Ti iI., iri-,i' [ ri-_..-i T -'-l -
F h i' : ,,- 1"' .-'"'" L_-.
1- W ilscu, i L PL-1 i. .i j Ei r., 'l L- I" 1"i It -I FT
.Ple-C F .:-F ,iJ--I


Figure 3-3. PROJECT page showing a list of projects available on the UF/FDOT online
database.









3.2.1 General Page

The GENERAL page summarizes the entire project information, and can be

classified into:

1. Project Overview.
2. Pile Description.
3. Insitu test and analysis.


3.2.1.1 Project overview

Information falling under this category includes project name, project number,

submitting company, submitting engineer, and comments. These give a general overview

of the project.

3.2.1.2 Pile description

Information describing the pile such as outer diameter, shell thickness, total length

of pile, and pile material fall under this category.

3.2.1.3 Insitu test and analysis

Types of insitu test available from the project, pile top elevation, pile tip elevation,

water elevation, mudline elevation, embedded length of the pile, major soil type, and plug

status fall under this category.

The insitu test data could be from CPT, SPT, or CPT/SPT (both CPT and SPT). In

case of CPT/SPT, the insitu test and soil page would be CPT test by default, with an

option of viewing or entering SPT data. This has been further described in section 3.2.3.

The two options for the plug status are plugged, and unplugged; these have been created

as drop down window in the data entry page.











General fLoad Test FInsitu test and soil Sod Plu2 Dnvine FAnalysis and results 1


Project Name Chesapeake Bay Bridge LT-1
Project Nuber
Submitting Company Tidewater SKANSKA
Submitting Engineer Tidewater SKANSKA
Comments Total of six tests
Outer Diameter 54-inch
Shell Thickness 6-inch
Insitu Data CPT/SPT
Pile Top Elv +17 3-ft
Pile Tip Elv -166 7-ft
Water Ely O-ft
Mudline Elv -27-ft
Total Length of Pile 184-ft
Embedded Length of Pile 139.7-ft
Pile Material Prestressed Concrete Pile
Major Soil Type Sands and Silts
Plug Status Plugged

Project List


Figure 3-4. Shows the format of the General page.

3.2.2 Load Test Page

The three columns in this plot are Time (minutes), Force (Tons), and displacement

(inch). The view graph page uses the JavaScript application in plotting the two columns

force and displacement (Figure 3-6).

The Go to Strain Data link at the top of the page tabulates the data from the strain

gages. The three columns on the STRAIN DATA page are the Time (min), Depth of the

strain gage from the top of the pile (ft), and the force (Tons) transferred to pile at that

depth (calculated using strain gage data). The view graph option plots the load along the

length of the pile. The Go to Main Data link brings the user back to the main load test


page.











General Load Test 7Insitu test and soil Soil Plug Driving Analysis and results


U(o to Strain Data


Time (min) Force (Tons) Displacement (inch)
50 0.01
100 0.01
150 0.015
200 0.015
400 2.25
300 2.24
200 2.21
100 2.2
0 22.2


View Graph

SProject ust


Records 1 to 43 of 43


Figure 3-5. Shows the format of the Load test page.


500
-^
,,


Load Test Data


Displacement (x 10- in)


Figure 3-6. Shows a plot of load displacement of the pile.


l1rapn appleI vy Iapns-nam com











General rrLoad Test flInsitu test and soil Soil Plug lDrnving TAnalysis and results I


Go to Main Data

Time (min) Depth (ft) Force (Tons)
5000 -13 5 528.0514596
-45.5 509.8427886
61 5 236.7127233
10000 -13 5 598.5016748
-45.5 580.3652605
-61 5 217.6369727
15000 -13.5 658.1133954
-45 5 658.1133954
-61.5 292.4948424
20000 -13 5 819.3901959
-45.5 801.1815249
-61.5 364.1734204
25000 -13 5 939.3362034
-45.5 921.2720457
-61 5 379.3473129
30000 -13.5 1043.530265
-45 5 1025.538364
S-61.5 359.8380225


View Graph

Project List


WRecords 1 to 18 of 18

Figure 3-7. Shows a screen shot of the strain data page.

3.2.3 Insitu Test and Soil Page

Based on the insitu test information on the General page, the type of insitu test page

will open. In case of CPT test, the page opens up with six columns namely elevation,

depth, soil type, cone resistance, friction resistance, and friction ratio. The page has an

option of plotting a graph of cone resistance vs. elevation, and skin friction vs. resistance

at the bottom of the page.












General FLoad Test Insitu test and soil Soil PluE F Drnvie Analysis and results I


Go to SPT


Ele Depth Cone Friction Friction
(et) (pt) Soil type resistance resistance fs ratio
qc (tsf) (tsf) Rf

-27 0 Silt Dark Gray to black, Very
soft

29 -2 Silt Dark Gray to black, Very 4 -0 01
soft


-139 -112 Sand Green Dense to Very 45 0 075
Dense

-141 -114 Sand Green Dense to Very 20 0 25
Dense

-143 -116 Sand Brownish gray to green, 155 0 15
v dense


Graph of Cone Resistance vs Elevation

Graph of Friction Resistance vs Elevation


Records 1 to 59 of 59


I ProLjet st


Figure 3-8. Screen shot showing the insitu test page for CPT data.


Figure 3-9. Plot of Cone resistance Vs elevation.


oad Test De










In case of SPT test the page has four columns: elevation, depth, soil type and

uncorrected blow count (N). An option of plotting blow count vs. elevation is available at

the bottom of the page.

In case there are both CPT and SPT data available from the test, the insitu data

page opens up with CPT data, and an option to go to SPT data.


General Load Test Insitu test and soil Soil Plug Dnving fAnalysis and results


Go to CPT


Graph ofN vs Elev


Records 1 to 54 of 54


i FroletU st


Figure 3-10. Screen shot showing the format for the SPT page.


Elev Depth Soil type N
(ft) [t)


-27 Silt Dark Gray to black, very
soft


-29 -2 Silt Dark Gray to black, very
soft


161 -134 Silt and Sand Greemnsh Gray 39

161 152 SandSandGreshGray
-152 Silt and Sand Greenish Gray 85
179











GIraph apple by raphsChart oom
Lod Test Data







179






-129- --- ^------------------------------------






0 50 100




Figure 3-11. Plot of blow count Vs elevation.

3.2.4 Soil Plug Page

The soil plug page has information on the status of the plug (plugged or


unplugged), plug height from the mudline (hm), plug height from the tip (ht), type of soil


at the tip, and the soil type at the mudline.




Mudline


hm





Soil Plug ht


Figure 3-12. Description of the parameters used in defining the soil plug.











General 7Load Test -Insitu test and soil -Soil Plug 'Driving Analysis and results 1


Project ust


Figure 3-13. Screen shot of the soil plug page.

3.2.5 Driving Page

The driving page has information such as the type of hammer, weight, energy, pre

bored depth, last blow, end of driving, and start of re-strike on it.


\M General Load Test Insitu test and soil FSol Plug r Drving Analysis and results |


Hammer Type Raymond 60 X Air/Steam Hammer
Weight 60,000-lbs
Energy 150,000-ft-lbs
Pre Bored Depth
Last Blow
End of Driving
Start of Restrike

I ProjectL Ust


Figure 3-14. Screen shot of the driving page.


Pug Status Plugged

Plug Height Mudline 13-ft

Plug Height Tip 126 7-ft

Soil Plug Tip Silt and Sand

Soil Plug Top Silt and Clay












3.2.6 Analysis and Results Page


The analysis and results page has information on the assumptions used in the data


reduction. Results of the analysis such as skin friction, and end bearing are also


presented.


General 7 Load Test 7 Insitu test and soil SolA Plug 7 Dnvgr Analysis and results


Soil Description Silt and Clay
Skin friction 15-tsf

End bearing 8.8-tsf


We define capacity as recommended by AASHTO and FHJA
inches

S= M + D/301

S = Pile Head Movement in inches

H = Elastic deformation PL/AE

P = Test Load (Kips)


for piles greater than 24







LJ


Figure 3-15. Screen shot of the analysis and results page.














CHAPTER 4
DATA REDUCTION

Data from the UF/FDOT cylinder pile database were separated into skin friction,

and tip resistance. This data had already been classified based on major soil type (insitu

test data), pile material, geometry of the pile (i.e., outer diameter, and shell thickness),

and the plug status (discussed in section 2-1).

The two methods used in separating the load test data into unit skin friction and tip

resistance were,

1. Direct Method: By reducing strain gage data from instrumented cylinder piles.

2. Indirect Method: By reducing load Vs deflection data using Davisson's and
deBeer's Method.

4.1 Data Reduction Using Strain Gages

Strain gages are either surface mounted, or embedment type, and are installed in/on

the pile, in order to determine the ultimate skin friction value in each of the soil strata. As

an axial load is applied to the pile, some percentage of the load is transferred to the

surrounding soil; beginning in the uppermost stratum, and the remaining percentage of

the load is transmitted down to the lower stratum, through the pile. As the applied load is

increased, a greater percentage of the load is transferred to the lower strata and,

eventually, to the pile tip.

The unit skin friction value along any portion of the pile is calculated as the

difference in the load between two adjacent strain gages divided by the surface area of

the pile between the gages, that is,









f= (Pi-P2) / (C*L1-2) Eq.4-1

f = Unit Skin Friction (tsf)

P = Load from strain gage 1 (Tons)

P2 = Load from strain gage 2 (Tons)

C = Circumference of the pile (ft)

L1-2 = Length between gages (feet)

The calculation of the load from a strain gage is derived from Hooke's law, and

algebraic substitution utilizing the basic principals from mechanics of materials, stress

and strain. For the initial straight line portion of stress-strain diagram, the stress is

directly proportional to the strain; that is,

C = E 8 Eq.4-2

y = Stress (ksi)

E = Modulus of Elasticity (ksi)

s = strain (in/in)

The stress in a structural member is obtained by dividing the magnitude of the load

by the cross sectional area,

y = P/A Eq.4-3

y = Stress (ksi)

P = Load (kips)

A = Cross-sectional area (sq-in)

A structural member responds to stress by straining, which is the ratio of total

deformation of the member to the total length of the member, or:

S= 6/L Eq.4-4










s = Strain (in/in)

6 = Total deformation under load (in)

L = Length of member (in)

Substituting P/A for o in Hooke's Law (Equation 2) results in:

P/A=E*s

Or,

P=E*s*A


Eq.4-5


The elastic modulus and the cross-sectional area of the pile are known, and that

the strain has been determined from the relationship between frequency and deformation

from the strain gage, simple multiplication returns the load in the pile at the location of

the strain gage.

The unit skin friction value can then be determined from Equation 4-1 where the

difference in load (P1-P2) between any two levels of strain gages is divided by the

perimeter area of the pile between them (i.e., C L1-2).

Load Desipation Curve


I)-6 -0 &--- -600 % TOW -I O











Load (kips)


---5000 sec
--- 1000sec
15000 sec
20000 sec
---25000sec
----30000 sec


Figure 4-1. A plot of load distribution along the pile Vs strain gage elevation with
increment in axial load/ time for the St. Georges Island Bridge Replacement
project.


0
-10
-20
-30


-50

-60
-70


0









Data from strain gages is available from four load tests performed at St. Georges

Island Bridge Replacement Project, and three tests performed at the Woodrow Wilson

Bridge Project.

4.2 Data Reduction Using Davisson's and DeBeer's Method

To reduce unit skin friction and end bearing in the absence of data from strain

gages, the Davisson's method was used in conjunction with DeBeer's method.

4.2.1 Davisson's Method

FDOT recommends (also recommended by AASHTO and FHWA) that

compressive axial load test data be evaluated by the method proposed by Davisson. For

piles greater than 24 inches in diameter, the ultimate load that a pile can resist is that load

which produces a movement of the pile head equal to:

S = A + D / 30 Eq.4-6

S = Pile head movement (inch)

A = Elastic deformation or (P L) / (A E)

P = Test load (kips)

L = Pile length (inch)

A = Cross-sectional area of the pile

E = Modulus of elasticity of the pile material (ksi)

D = Pile diameter (inch)

A pile of length (L), area (A), and Young's Modulus (E) is considered as a fixed

base, free standing, column for purpose of making a calculation of elastic deflection. The

elastic deflection line is then plotted as shown and serves as an index for interpreting the

load test. Furthermore, on the load deformation plot, the failure criterion offset is plotted










parallel to the elastic deformation line (at a distance D/30 inch away) and the point at

which the load-deflection curve intersects the failure criterion line is the ultimate

capacity, or the failure load.


St. Georges Island Bridge Replacement Project


4000

3500

3000

2500

2000

1500

1000

500

0


0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2 3.6 4
displacement (inch)


Figure 4-2. Determining capacity of pile, using Davisson's method, for the St. Georges
Island Bridge Replacement Project, Load Test-1.

4.2.2 Back Computed Skin and End Bearing Values

Once the FDOT ultimate capacity for the load test had been computed, the

contribution of skin, and tip towards this load had to be identified. This was achieved by

the DeBeer's method.

The method proposed by DeBeer (1967) and DeBeer and Wallays (1972), suggests

that in a load distribution curve the capacities from skin friction and end bearing can be

separated into two separate curves of different orders of magnitude as shown in figure 4-










3. We can get back the original load deformation curve by superimposing the two

individual curves.



Actual load deformation plot





-/ Skin Friction Dart

End Bearing Part



Displacement


Figure 4-3. Separation of load vs. deformation plot into skin and tip.

Taking advantage of this fact, if the load deformation curve is plotted on a double

logarithmic scale the values fall on two distinct approximate straight lines, the

intersection of which gives the start of end bearing, as shown in figure 4-4. On this

double logarithmic plot, the part of the curve before the intersection (first half) consists of

contribution to the total capacity mainly from skin friction, the part of the curve (second

half) after the intersection corresponds mainly to contribution from end bearing.


Sgooo Second Half

FirstHalf 1^.

100

0 Start of End
Bearing =
310 Tons

---------------------------
0.01 0.1 1 10
Log (disp)
Figure 4-4. Separating skin friction and end bearing using DeBeer's method.









Table 4-1. Contribution of skin and end bearing in DeBeer's.
Contributions First Half Second Half
Major Contribution Skin Friction End Bearing
Minor Contribution End Bearing Skin Friction


For the analysis the load corresponding to the intersection of the two parts of the

curve on the double logarithmic scale was taken as capacity from skin friction. One of the

most common problems with this method is that, in some cases, the two straight portions

in the graph are not clearly defined.

Typical, but hypothetical, load settlement records are shown in Figure 4-5. This

provides a very rough estimate of contributions from skin friction and end bearing. In the

case of a frictional pile plunging occurs at the failure load and a wide range of settlement

exists over which essentially the same failure load would be determined if a settlement

criterion were used to indicate ultimate load. In the case of a point bearing pile the curve

usually exhibits an increase in load with increase in settlement up to extremely high

settlements. This is the source of much difficulty in the interpretation of pile load tests. A

pile with significant amounts of both point bearing and skin friction will generally plot,

bounded by pure point bearing and pure friction as limiting conditions (High Capacity

Piles, Davisson, M.T).

4.3 Comparison Between Direct and Indirect Method

Data from strain gages were available from seven tests (four from St. Georges

Island Bridge Replacement Project, and three from Woodrow Wilson Bridge Project).

Both direct and indirect methods were used in reducing skin friction, and tip resistance

for these tests. The two methods showed good agreement. Table 4-2 shows a comparison

between the two methods.











LOAD

S_.FRICTION PILE

POINT +
FICTION 2001
S POINT
-'~_BI HEARING ELASTIC
DEFLECTION

CRITERION

-J
W
U,


A, E
L CR ITERION:
0.15 in. + Q(IP
B For B=lft. QTpO. I in.
IN MOST SOILS

PL
Elastic Deflection, 8* A

Figure 4-5. Interpretation of Pile load test. (High Capacity Piles, M.T Davisson)
No strain gage data in calculating unit end bearing indicates that the strain gage at

the tip failed to produce reliable data during the static loading process, and was not taken

into account for calculation as identified in the load test report (St. Georges Island Test-2,

Woodrow Wilson-C, Woodrow Wilson-I).









No data from Davisson's (unit end bearing) method or DeBeer's (unit skin friction)

method indicates that the load test was not taken to failure so as to interpret the

contribution of skin and tip to the total capacity.

Table 4-2. Comparison between direct and indirect method.
Proj ectUnit Skin Friction (tsf) Unit End Bearing (tsf)
Project Name
Strain Gage DeBeer's Strain Gage Davisson's Method
St. Georges Island-1 0.99 1.17 38.4 24.9
St. Georges Island -2 0.28 N.A N.A N.A
St. Georges Island -3 0.12 N.A 81.69 N.A
St. Georges Island -4 0.85 1.51 48.852 49.822
Woodrow Wilson Bridge-C 0.42 0.53 N.A N.A
Woodrow Wilson Bridge-F 0.93 0.85 58.8 51.9
Woodrow Wilson Bridge-I 0.81 N.A N.A N.A














CHAPTER 5
ESTIMATION OF SOIL PLUG

Open-ended piles are widely used in offshore construction. During the initial stage

of installation, soil enters the pile at a rate equal to the rate of penetration of the pile. As

penetration continues the inner soil cylinder may develop sufficient frictional resistance

to prevent any further soil intrusion, causing the pile to become "plugged". Although

technically the inner soil can be referred to as a "plug" only when it prevents entry of

additional soil during penetration, the term "soil plug" is commonly used in reference to

any soil mass inside the pile, regardless of its state during installation (Paikowsky, 1990).

The soil plug has to be estimated in order to determine the end bearing, and the

mass of the cylinder pile. The end bearing is required for determining the capacity, and

the mass of the pile is required in the drivability analysis.

A Finite Element Model of a cylinder pile penetration was modeled using ADINA

(i.e., Automatic Dynamic Incremental Non-Linear Analysis). The properties of this

model were based on data from the St. Georges Island Bridge Replacement Project.

5.1 Formation of Soil Plug

Various researchers have explained the formation of the column of soil within the

pile. The two most popular theories are:

1. Arching phenomenon.
2. Inertial forces on the soil plug.









5.1.1 The Arching Phenomenon

During soil plugging within the pile there is an increase in the local resistance in

the lower zone of the plug. When this resistance exceeds the tip bearing capacity, the pile

plugs preventing further soil penetration. The increased resistance was explained by using

the arching phenomenon (Paikowsky et al., 1990).

The arching mechanism is based on the reorientation of the granular soil particles

into an arch formation. The arch has a convex (upward) curvature in the upper zone,

attributed to a bulb of reduced stresses during the piles initial penetration. The arch has a

concave (downward) curvature at the tip of the plug, attributed to a bulb of increased

vertical stresses due to penetration in a plugged or a semi-plugged mode (Figure 5-1).

Such an arrangement when subjected to loading, leads to load transfer into the soil

mass. With loads exceeding the arch capacity, dilation and shear take place along the

arch, allowing penetration of additional soil until a new stable arch forms, for which the

arch resistance exceeds the upward pushing forces (tip capacity). This process accounts

for zones of varying densities with in the pile. In all plugged piles the densest soil zone

exists a quarter diameter away from the tip. However, in case of unplugged piles the

densest zone exists at the tip and the density decreases from the bottom upwards.

Pile Section

Soil Plug

SActive convex arch



]--Passive concave arch

Figure 5-1. Isobars of the vertical stress with in the soil plug, showing the transition from
active to passive arching.









5.1.2 Inertial Forces on the Soil Plug

The forces acting on a soil plug during static loading (A) differ from those that act

during driving (B), and it is important to distinguish between the two conditions.


W


Figure 5-2. Free body diagram of soil column with in the pile during, A) Static loading,
and B) Pile Driving.

The free body diagram in Figure 5-2 shows the force system in both cases.

The forces acting on the soil plug are:

1. Frictional force: The soil plug feels this force, in the downward direction, on the
pile soil interface. Its magnitude (Fs) is equal to the product of the plug surface
area, times the unit skin friction value at the interface. As this study was carried out
to see the effects of soil plug diameter, and g-forces on the soil plug height, the
interface frictional coefficient was chosen to be a constant value for the parametric
study (Based on design curves for cylinder pile, discussed in chapter-6).

2. Weight of the soil plug: The weight (W) of the soil plug is the product of the
volume of the soil plug, times the total unit weight of soil. This force acts in the
downward direction.


W



v


t t









3. Tip Resistance: The tip resistance acting on the soil plug is equal to the product of
the plug cross sectional area, times the unit tip resistance. This force acts in the
upward direction trying to un-stabilize the plug.

4. Inertia Force: The inertial force is equal to the product of the plug mass, and the
plug acceleration, and represents the resistance of the plug weight to the downward
acceleration imparted by the hammer to the pile-plug system. The inertial force acts
in the upward direction, trying to oppose the motion, and creating a resultant
upward force. If the inertial effects are large enough, the pile will continue to core.
The inertial force acts only during the driving process.

The assumptions made in these calculations are:

1. The g-forces on the soil plug is constant for the full length, and its value equal to
the average g-forces on the embedded portion of the pile.

2. The damping forces were ignored for the calculation purpose as discussed in
section 5.3.4.

5.1.2.1 During static loading

The forces acting during static loading are as follows:

Fs+W= Qt Eq.5-1


(zDfs)Lp +( )Lp = ( ) qt Eq.5-2
4 4

Lp {fs + 0.25/D) = 0.25qtD Eq.5-3

0.25qtD
Lp = Eq.5-4
(fs + 0.257D)

Lp = Length of the plug (ft).

D = Diameter of the plug/ inner diameter of the pile (inch).

y= Total unit weight of soil (pcf).

fs = Unit skin friction between the plug and pile (tsf).

Fs = Total skin frictional force (Tons).


qt = unit end bearing at pile toe (tsf).









Qt = Total tip resistance on the soil plug (Tons).

W = weight of the soil plug (Tons).

5.1.2.2 During driving

The forces acting during driving are as follows:

Fs+W= Qt+I Eq.5-5

D 2 y 7rD2 D2 Lp *ap*g
(IDfs)Lp + ( )Lp = ( )qt + ( )Eq.5-6
4 4 4 g

Lp{fs + 0.25yD 0.257D ap) = 0.25qtD Eq.5-7

0.25qtD
Lp = Eq.5-8
(fs + 0.257D(1- ap))

ap = average plug acceleration in g's.

Equation 5-8, explains plug heights increase with increase in soil plug diameter

(accountable to inertia of the soil plug). A simple case study performed by Stevens

showed that if the average plug acceleration is greater than 22g, the pile will not plug

during driving. Average peak accelerations ranging from 169 to 215g have been

measured during the driving of large diameter offshore piles (Stevens, 1988).

Equation 5-4, accounts for plugging once the pile is subsequently loaded

statically, as the plug will have considerable resistance to movement, since the shaft

resistance greatly exceeds the end bearing that can be mobilized by the soil plug.

5.1.3 Parametric Study Effects of Diameter, and G-Forces

Figure 5-3, shows a screen shot of the mathcad file developed based on equation 5-

8 to study the effects of pile diameter, and acceleration due to gravity of the soil plug on

plug heights.










The input parameters are the outer diameter of the pile, shell thickness (to calculate

the diameter of the soil plug), soil type (same classification as SPT2000), SPT N values

for unit skin friction, and unit end bearing calculations, and submerged unit weight of

soil.


OD := 54 inch t := 8 inch ap:= 1 g
unitweight
unitweight:= 50 pcf unitweigh:=
2000
type := 3 Nskin:= 25 Ntip:= 30

(OD 2.t)
D:= D = 3.167 ft
12
calculates the diameter of the soil plug in terms of pile

fs:= .621n(Nskin) .9922 if type = 1 qt
.5211 -n(Nskin) .79S9 if type = 2
.025-Nskin- .039 if type = 3
.0188Nskin- .0296 if type = 4
.0152-Nskin .016 if type = 5
fs = 0.586 tsf qt =


PLcalc =


.25. qt. D


Soil Type Pile Material Type
clay concrete 1
clay steel 2
silt concrete 3
sand concrete 4
sand steel 5


Dimension

:= .2226 Ntip
.2226 Ntip
.4101-Ntip
.5676. Ntip
.5676. tsfp
12.303


type = 1
type = 2
type = 3
type = 4
type = 5


PLeak = 16621 ft


[fs + unitweight.-D.25-(1 ap)]

S. D2. PLcalc unitweight qt. .D2
Qb:= fs--D-PLcalc W := Q:= I:= W. ap
4 4
Qb = 96.896 Tons W= 6.545 x 103 Tons Qp = 96.896 Tons I= 6.545 x 103 Tons
NettUpwardForce := I + Qp NettUpwardForce = 6.642 x 103 Tons

NettDownwardForce := W + Qb NettDownwardForce = 6.642 x 103 Tons


Figure 5-3. Screen shot of the MathCAD file showing plug height, upward force, and
downward force calculations.

Parametric study was carried out on piles of six different diameters (54", 38", 24",

20", 16", and 12"), and the g-forces varied from 0-g (static loading case) to 45-g. Table

5-1 tabulates the various parameters and their values.









Table 5-1. Fixed parameters in study, and values.
Parameter Value
Soil Type Silt
Pile Material Concrete
SPT N Value for Skin 25-blows
SPT N Value for Tip 30-blows
Pile Length 80-ft


Plug Height Curve


120



100


0 10


* ID=54" -U- ID=38"


20 30 40
average g-force on soil plug
ID=24" ID=20" -- ID=16" -*- ID=12"


Figure 5-4. Variation of plug height with soil plug diameter and g-forces.

Figure 5-4, plots the plug heights for soil diameters (inner diameter of the pile) of

54-inch, 38-inch, 24-inch, 20-inch, 16-inch, and 12-inch using equations 5-8 (MathCAD

output).









The intersection of the soil plug curve with the 80-ft line (pile length) corresponds

to the "critical g-force value". At g-force values above the critical g-force value there will

be no plug formation, at g-force values below the critical g-force value a plug will form,

the length of this plug will be directly proportional to the g-force that the plug

experiences during the driving process. Smaller diameter piles have smaller plug heights

as compared to large diameter piles (i.e., smaller diameter piles plug faster than a large

diameter pile).

Table 5-2. Critical g-force values with diameter.
Soil Plug Diameter Critical g-force Value
54-inch 15-g
38-inch 24-g
24-inch 42-g
20-inch <45-g
16-inch <45-g
12-inch <45-g


From this study it is clear that the plug height is very sensitive to the volume of soil

within the pile (i.e., square of the inner diameter), and acceleration due to gravity of the

soil plug. This would result in large diameter piles cutting through soil (unplugged) rather

than forming a plug. Change in soil type (sand, clay, and silt) was not an impacting factor

in this study (soil type varied for same blow counts giving different fs values).

5.2 ADINA Theory and Modeling

The pile model was completely described, including the geometry of the model,

material properties, boundary conditions and loads using the pre-processor ADINA-IN

and analyzed using the structural analysis program ADINA of the AUI System (i.e.,

ADINA User Interface).









5.2.1 General Overview of the Pile Model

The pile was modeled as a two-dimensional, nine node, axisymmetric solid

element. The axisymmetric element provides for the stiffness of one radian of the

structure.

ADINA models the elements as isoparametric displacement-based finite elements.

The principal idea of using an isoparametric finite element formulation was to achieve

the relationship between the element displacement at any point, and the element nodal

point displacement directly through the use of interpolation function (also called the

shape function).

A Local Cartesian coordinate system was used in defining the model points. The

pile had two degrees of freedom, the translation in the yz-plane. The points were then

bound together using a vertex surface to define the pile. A vertex surface is one whose

geometry is defined by points (unlike a patch surface whose boundary is defined by

lines). The sides of the pile coming in contact with the soil were defined as fluid-structure

boundaries (section 5.3.3).



Z Yxy= 0

Yxz= 0

X Y esxx = u/y


Figure 5-5. Isoparametric Nine Node Axisymmetric Element









5.2.2 Material Model of the Pile

The elastic isotropic material model was used to describe the pile. The two material

constants used to define the constitutive relation were E (i.e., Young's Modulus), and v

(i.e., Poisson's Ratio).

5.2.3 Properties of the Pile

The model pile was assigned values based on data from the St. Georges Island

project. The average penetration of the pile, taking into consideration the time intervals

between blows, was taken to be roughly 0.4inch/sec, which is comparable to the soil

penetration rate recommended for deep, quasi-static penetration tests of soil (0.4-0.8

inch/sec, ASTM 1979). Further, a range of values was chosen for the pile property so as

to carry out a parametric study. This study was used to find out the factors impacting the

formation of a plug within the pile and their extents. Table 5-3 summarizes the properties

of the pile and the variations.

Table 5-3. Pile Properties and its variations
Pile Property Actual Model Parametric study Model
Pile Length 80 ft 80 ft
Outer Diameter 54 inch 36 inch- 60 inch
Shell Thickness 8 inch 10 inch- 6 inch
Young's Modulus 6300 ksi 6300 ksi
Poisson's Ratio 0.15 0.15
Unit Weight 150pcf 150pcf
Rate of Penetration 0.5 inch/sec 0.3 inch/sec- 0.5inch/sec


5.2.4 Pile Formulation

The pile was formulated using the Lagrangian coordinate system. In this

formulation, the mesh moves with the material particles. Hence, the same material

particle was always at the same element mesh point. In order to recreate the pile

penetration process, keeping in mind the modeling constraints, the top end of the pile was









held fixed and the soil was pushed from the bottom boundary with traction of 100psf, so

as to give the pile a relative downward movement of .5inch/sec (section 5.2.3).





















Figure 5-6. ADINA pile input, thick lines indicating contact surface

5.3 ADINA-F Theory and Modeling

The soil properties, boundary conditions, and pile loading were modeled using the

ADINA-F (i.e., ADINA-Fluid) feature of the AUI system. The soil boundary was chosen

larger than 7.5 times the pile diameter so as to avoid boundary effects as suggested by

Vipulanandan et al. (1989).

5.3.1 General Overview of the Soil Model

The soil was assumed to be an inviscid axisymmetric two-dimensional steady

state flow problem, where the soil particles move along streamlines around the pile as

modeled by Azzouz et al. (1989). A total of five vertex surfaces were used to define the

soil mass.









5.3.2 Material Model of the Soil

"Constant property" material model was used to define the soil mass. Variations

were later made in the properties of the soil so as to carry out a parametric study. The

loose and dense sand behavior of soil was modeled using the compressible and

incompressible flow types. 561 nodes were used in defining the entire soil mass.

5.3.3 Boundary Condition

A no slip boundary condition was applied along the pile soil interface so as to

introduce shearing action between the pile and soil (surface 1, 2, and 3).

A slip surface was introduced on boundary surfaces that defined the soil mass (4

and 5).






1 3



2

4 5







Figure 5-7. Figure showing the slip and no slip surfaces along the various boundaries

5.3.4 Properties of the Soil Model

Chow suggested that, with a proper representation of soil hysteresis using very

simple parameters like Young's modulus (E), Poisson's Ration (v), Shear Strength (Cu)

and by incorporating the soils mass density (p), typical pile driving responses could be









recovered without resorting to any other soil damping and stiffness parameters such as J

and Qu in the original E.A.L Smith model. (I.M Smith and S.M Wilson, 1981).

Table 5-4 summarizes the properties of the soil and the range of values chosen for

carrying out a parametric study.

Table 5-4. Soil Properties and its Variation
Soil Property Actual Model Parametric Model
Unit Weight 100pcf 80pcf-120pcf
Friction Angle/ Dynamic Shear 28degree/ 500pa-sec 28degree/ 500pa-sec -
Strength 35degrees/ 2000pa-sec


5.3.5 Soil Formulation

The soil particles can undergo very large displacements and were formulated using

the Eulerian coordinate system.





















Figure 5-8. Showing an ADINA-F soil mesh

In the Eulerian formulation, the mesh points are stationary and the soil particles

move through the finite element mesh in the prescribed direction. In this formulation,

attention is focused on the motion of the material through a stationary control volume and









that we use this volume to measure the equilibrium and mass continuity of the soil

particles.

5.4 ADINA-FSI Theory and Modeling

The ADINA pile model and the ADINA-F soil model were merged together using

the feature of ADINA-FSI (i.e., Fluid Structure Interaction). In FSI, the fluid forces (soil)

are applied onto the solid (pile), and the solid deformation changes the fluid (soil)

domain. The pile was based on the Lagrangian coordinate system, and the soil was

modeled using the Eulerian coordinate system. For the FSI model, the coupling was

brought about based on the arbitrary-Lagrangian-Eulerian (ALE) coordinate system.

When any part of the computational domain is deformable, the Eulerian description

of soil (fluid) flow is no longer applicable and the Lagrangian description must be used.

Anywhere else in the soil (fluid) domain, the fluid flow can be described in an arbitrary

coordinate system as long as it meets the coordinate requirements along the boundaries.

Such a description is called an arbitrary-Lagrangian-Eulerian formulation and was used

in the FSI modeling. In an arbitrary-Lagrangian-Eulerian formulation, the mesh points

move but not necessarily with the material particles. In fact, the mesh movement

corresponds to the nature of the movement and is imposed by the solution algorithm.

While the finite element mesh spans the complete analysis domain throughout the

solution and its boundaries move with the movements of free surfaces and structural

boundaries, the soil particles move relative to the mesh points. The approach allows the

modeling of interaction between soil and pile.










B)

-Fluid Structure Interface


Axisymmetric pile section


Soil


Figure 5-9. Contact surface geometry: A) Axisymmetric section of a cylinder pile
showing the contact surfaces, B) section showing interface elements.

5.5 ADINA Plot

The results of the ADINA-FSI were then viewed using the post processor ADINA-

PLOT. Figure 5-10 shows the plot files for both pile (ADINA) and soil (ADINA-F).


Soil Plug


Cavity for Pile


B


Figure 5-10. ADINA Plots: A) Plot of the pile as generated by ADINA, B) Plot of the soil
mass as generated by ADINA-F, showing the cavity where the pile is placed
in the ADINA-FSI model.


F









Information such as nodal velocities at the ten nodes on the plug surface and

stresses with in the pile was then monitored.


ADINA-IN (Pre-processor)

ADINA (Pile formulation) ADINA-Fluids (Soil formulation)

ADINA-FSI (Merging the soil and pile models)

ADINA-PLOT (Viewing and analyzing the output)


Figure 5-11. Flow chart indicating the various steps in the analysis of the plug

5.6 Factors Affecting the Soil Plug

In order to estimate the factors impacting the length of the soil plug the following

soil and pile parameters were varied

1. Shell thickness.

2. Outer diameter of Pile.

3. Rate of penetration of the pile.

4. State of Soil (loose or dense).

5. Dynamic shear strength of soil.

6. Unit weight of soil.

5.6.1 Assumptions in Estimating the Soil Plug

The assumptions for estimating the height of the soil plug were based on

information from the St. Georges Island Bridge Replacement Project.

In the St. Georges Island Bridge Replacement project, the soil within the pile did

not form a plug. Identical results were obtained from the ADINA-F model using

properties listed in table 5-2 and table 5-3.








The soil within the pile rose to the full pile length of 80 feet (100% Plug height).

At 100% plug height, the soil within the pile reached a terminal velocity, which was

about 5 times less than the initial velocity within the pile. Also, at this stage the

maximum velocity in the pile soil system was about 70 times the velocity of the soil plug.










tn IT






Figure 5-12. Velocity profile with in the finite element model: A) Velocity profile with in
the finite element model, pile stationary, and soil moving, B) Velocity profile
with in the model, pile moving, and soil stationary.
In Figure 5-12, the length of the arrows is proportional to the magnitude of the

velocity. The thick arrow represents the maximum velocity zone, Vmax.

Figure 5-12 a, shows the velocities in the system during the plugged stage, in the

actual finite element model. The pile is stationary (has zero velocity). The lowest soil

particle velocity is that of the soil plug, which is zero, or in case of partially plugged it is

a small upward one, Vp. The highest velocity is that of the soil particles furthest from the

pile surface (boundaries are slip surfaces), Vmax.

The finite element model shown in Figure 5-12 a, is translated into an actual pile

penetration process by subtracting the entire system velocity by a downward Vmax, as









shown in Figure 5-12 b. With the result, the pile moves downwards with a velocity of

Vmax. The plug moves downwards with a velocity of (Vmax-Vp) in case of partially

plugged, or Vmax in case of fully plugged.

Velocity Ratio (VR) = Velocity of the plug / Velocity of the Pile

(Vmax- Vp)
VR =(Vmax Vp) Eq.5-9
V max

Dividing, equation 5-3 by Vp we get,

Vmax
-1
VR= Vp Eq.5-10
Vmax
Vp

V max
From, St. Georges Island Project, = 70, Substituting in equation 5-4,
Vp

VR = 0.9857

0 < VR < 1 (VR = 1, Pile is plugged, VR = 0, Pile is unplugged).

A Velocity Ratio of 0.98 was the highest that was obtained using ADINA, and for

all-purposes this was taken as the stage of soil plug formation. At this stage the soil and

the plug are moving with the same velocity (relative velocity of zero).

Figure 5-13, shows the variation of velocity ratio with increase in % plug height.


%Plug, height PlugLength *100 Eq.5-11
PileLength

The % plug length (%PL) refers to the length of the plug relative to the length of

the pile and was a helpful modeling concept. By using the %PL, the tip elevation of the

pile could be kept constant for various plug lengths, and the movement of the soil

particles with in the pile could be monitored.










Velocity Ratio Vs % Plug Height


120

100

.0 80

a 60

0 40

20 -J
0
0 ----------------------

0.94 0.95 0.96 0.97 0.98 0.99 1

Velocity Ratio


Figure 5-13. Plot showing variation in velocity with in the pile with change in plug
height.

5.6.2 Unplugged Soil Velocity Profile

Two stages, once during un-plugged condition, and the other during plugged

condition, were chosen to show the difference in the velocity profile with in the pile. The

plots were made using ADINA-Plot, and a 32-color scheme option. Figure 5-14 shows

an axisymmetric pile section during the unplugged stage (plug height is 20% of the pile

length). The soil around the pile wall best indicates the velocity of the pile.

At this stage, when the pile is moving down with a velocity indicated by the blue

color profile (top end of the color scheme) the soil with in the pile is moving with a much

smaller velocity (lower end of the spectrum), this means that there exists a large relative

velocity between the soil plug and the pile, indicating that the pile has not plugged.















































Figure 5-14. Velocity profile with in cylinder pile- unplugged condition

5.6.3 Plugged Soil Velocity Profile

Figure 5-15, shows an axisymmetric pile section during the plugged stage (plug

height is 88% of the pile height). At this stage the terminal velocities have been reached.

A uniform velocity has been attained with in the pile whose value is almost equal to the

velocity of the pile. At this stage, the pile, and the soil with in, have almost zero relative

velocity indicating formation of soil plug (pile and soil plug moving together).


MlF67
Q10 1KO
O-D 133U
0-01D67
O-DOBDD









































Figure 5-15. Velocity profile with in cylinder pile- plugged condition

5.6.4 Variation in Shell Thickness

The geometry of the Pile plays an important part in the rise of soil with in the pile.

A parametric study was done with shell thickness varied from 10" to 6", with constant

outer diameter, 54". The results observed were in accordance with Kindel's theory that,

plug movements tend to stabilize due to decrease in the inside volume resulting from an

increase in the pile wall thickness (Paikowsky et al., 1990). This result also supports the

theory that pipe piles have a higher chance of plugging as compared to large diameter

cylinder piles, owing to a smaller inertial force (lesser soil plug mass) as discussed in










section 5.1.1. In Figure 5-16 the points marked X indicates the pile used at the St.

Georges Island Bridge Replacement Project. Loose sands were found to have slightly

larger plug heights as compared to dense sands.




Variation in Shell Thickness at constant diameter = 54"

120
100


I E Loose Sand










* Indicates standard pile used for comparison.
Outer Diameter = 54", Shell Thickness = 8", Unit Weight = 100pcf,
Dynamic Shear Strength/Friction angleDense Sand000pa-sec/30deg,
o. 40
20
0
10 *8 6
Thickness (inch)


* Indicates standard pile used for comparison.
Outer Diameter = 54", Shell Thickness = 8", Unit Weight 100pcf,
Dynamic Shear Strength/Friction angle= 1 000pa-sec/3 Odeg,
Rate of Penetration= 0.5inch/sec.
Figure 5-16. Plot showing variation of shell thickness with height of soil plug

5.6.5 Variation in the Outer Diameter of the Pile

To study the variation in diameter, the geometry of the pile was varied, but the ratio

of diameter to the shell thickness was kept constant, ratio of 6. A comparison between the

two piles with the same shell thickness and different diameters (8"-54" and 8"-48")

indicates that the pile with the smaller diameter plugs faster. This result was in agreement

with tests conducted by Kishida (1967).










Variation in shell thickness and diameter at constant
ratio = 6


8"-54" 8"-48"
shell thickness"-Diameter"


* Loose Sand
* Dense Sand


6"-36"


* Indicates standard pile used for comparison.
Outer Diameter = 54", Shell Thickness = 8", Unit Weight = 100pcf,
Dynamic Shear Strength/Friction angle=1 000pa-sec/30deg,
Rate of Penetration= 0.5inch/sec.
Figure 5-17. Plot showing variation in the soil plug with change in outer diameter

Table 5-5. Values used for pile outer diameter parametric study
Outer Diameter Shell Thickness Ratio


60
48
36


6
6
6


5.6.6 Variation in the Rate of Penetration of the Pile

The rate at which the pile is driven into the soil was found to have a considerable

impact on the height of soil plug in the pile. Parametric study was carried out with rates

varying from 0.3inch/sec to 0.5inch/sec. The following results were obtained.


90
80 -
70 -
S60 -
50 -
= 40-
S30-
20 -
10 -
0 -


10"-60"


I







59



Variation in Rate of Penetration

90
85
p 80
SI Loose Sand
5 S Dense Sand
7- 70
65
60
.5inch/sec .4inch/sec .3inch/sec
Velocity of Pile


* Indicates standard pile used for comparison.
Outer Diameter = 54", Shell Thickness = 8", Unit Weight = 100pcf,
Dynamic Shear Strength/Friction angle= 1000pa-sec/30deg,
Rate of Penetration= 0.5inch/sec.
Figure 5-18. Variation in Rate of Penetration

5.6.7 Variation in Shear Strength of Soil

Dynamic Shear Strength values of standard sand were obtained and compared

with the friction angle value (4). These values were varied for the purpose of parametric

study. The friction angle was found to be strong influencing factor. The plug heights went

up 40% when the friction angle was reduced from 35 degrees to 27.5 degrees.







60



Variation in Dynamic Shear Strength


100 -I


40 -


* Loose Sand
* Dense Sand


X: 500 pa-sec 1000 pa-sec 1500 pa-sec or 2000 pa-sec or
or 27.5degree or 30degree 32.5degree 35degree
Dynamic Shear Strength or Friction Angle


* Indicates standard pile used for comparison.
Outer Diameter = 54", Shell Thickness = 8", Unit Weight = 100pcf,
Dynamic Shear Strength/Friction angle=1000pa-sec/30deg,
Rate of Penetration= 0.5inch/sec.
Figure 5-19. Variation in Friction angle or Dynamic shear Strength

5.6.8 Variation in Unit Weight of Soil

The density of soil was varied from 80pcf to 120pcf. The following results were

obtained. These results contradicted the fact that dense sands have a smaller plug height


as compared to loose sands.








Variation in Unit Weight


*1


80 pcf


100 pcf
Unit Weight (pcf)


* Loose Sand
* Dense Sand


120 pcf


* Indicates standard pile used for comparison.
Outer Diameter = 54", Shell Thickness = 8", Unit Weight = 100pcf,
Dynamic Shear Strength/Friction angle=1 000pa-sec/30deg,
Rate of Penetration= 0.5inch/sec.


Figure 5-20. Variation in Unit Weight of Soil


v















CHAPTER 6
SKIN FRICTION AND END BEARING CURVES

6.1 Unit Skin Friction and Unit End Bearing Curves

The load test data was reduced into unit skin friction and end bearing (as discussed

in Chapter-4), and plotted as a scatter plot against uncorrected blow counts (N),

corresponding to the soil type and pile material. Best-fit curves were drawn through the

scatters, and the curve corresponding to the best R2 (Regression coefficients) value was

chosen.

Five curves were formulated corresponding to skin friction:

1. Concrete piles in sands.
2. Steel piles in sands.
3. Concrete piles in clays.
4. Steel piles in clays.
5. Concrete piles in silts.

Three curves were formulated corresponding to end bearing:

1. In sands.
2. In clays.
3. In silts.















fs = 0.3084Ln(N) 0.4599
0.9
R2 = 0.8388
0.8
0.7


I-/
0.6
0.5
S0.4 -
S0.3-
0.2
0.1

0 5 10 15 20 25 30 35 40 45 50 55 60
SPTN Values




Figure 6-1. Skin friction (tsf) Vs N (uncorrected) for concrete piles in sand.


0.7

0.6 fs = 0.2028Ln(N) 0.2646
05 R2 = 0.8504"""
S0.5 1
0.4 suggested/ I
S0.4
0U Limit
0.3

S0.2

0.1 -

0!
0 5 10 15 20 25 30 35 40 45 50 55 60 65
SPT N Value




Figure 6-2. Skin friction (tsf) Vs N (uncorrected) for steel piles in sand.

............. Modified trend line.
- Suggested Limit.














I .0
fs = 0.5083Ln(N) 0.634
S1.4 R2 = 0.9448
S1.2

cl 1
I-
u- 0.8

r 0.6
C, ,
0.4

0.2

0 -
0 5 10 15 20 25 30 35 40 45 50
SPT N Value

Figure 6-3. Skin friction (tsf) Vs N (uncorrected) for concrete piles in clay.


1.2
fs = 0.4236Ln(N) 0.5404
v- 1-
S1 R = 0.8965

.2 0.8

u- 0.6

co 0.4

3 0.2

0
0 5 10 15 20 25 30 35 40 45 50 55
SPT N Value

Figure 6-4. Skin friction (tsf) Vs N (uncorrected) for steel piles in clay.

............. Modified trend line.
- Suggested Limit.




























0 5 10 15 20 25 30 35 40 45 50 55 60
SPT N Value

6-5. Skin friction (tsf) Vs N (uncorrected) for concrete piles in silts.


65


0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 10 10
0 5
SPT N Value


Figure 6-6. End bearing (tsf) Vs N (uncorrected) in Sands.

............. Modified trend line.

Concrete


-0 Steel


fs = 0.3265Ln(N) 0.2721 1
R = 0.8994

I
" I

I

*F I


1.4

1.2
LL.
80
o 0.8

0.6

0.4

0.2

0


Figure







66



5

qt = 0.2276x
L4
S4 R 0.9616
SI-
c3







0


1 2





10 -
qt =0.4101x
12
2 R2 = 0.8867
0
8
LL 6

U) 4

2

0
0 5 10 15 20 25 30 35
SPT N Value


Figure 6-8. End bearing (tsf) Vs N (uncorrected) for silts.


............. Modified trend line.


- Concrete


W 0Steel






67


6.2 Comparison of Skin Friction and End Bearing with SPT2000

In order to compare the cylinder pile design with the existing design used in the

SPT2000 program, six graphs were plotted namely, unit skin friction vs. SPT N values,

and unit end bearing vs. SPT N values for, clays, silts, and sands. Each curve consists of a

set of four curves, namely:

1. SPT2000 for small piles.
2. SPT2000 for steel pipe piles.
3. Large diameter cylinder pile, concrete.
4. Large diameter cylinder pile, steel.
















Unit Skin Friction in Clays


0 10 20 30 40 50 60
No Data zone SPT N Values
SPT N Values

--- SPT97, Concrete Piles -e- SPT97, Steel Piles -1- Large Diameter Pile, concrete A Large Diameter Pile, Steel


Figure 6-9. Comparison of various designs used for computing unit skin friction in clays.


- - - w - -
I--
-- U---- - -- A ~ -- -


A A A A
--- --- --


I















Unit Skin Friction in Silts


1.4


1.2




0
S0.8

0.6




0
U-



S0.4


0.2



0 10 20 30 40 50 60 70
- No Data zone SPT N Values
SPT N Values

--SPT97, Concrete Piles -- SPT97,Steel Piles -*-Large Diameter Piles, Concrete


Figure 6-10. Comparison of various designs used for computing unit skin friction in silts.














Unit Skin Friction in Sands


1.2


1


0.8












0
0 10 20 30 40 50 60 70
SPT N Values

--SPT97, Concrete Piles --SPT97, Steel Pile -- Large Diameter Pile, Concrete -A- Large Diameter Pile, Steel


Figure 6-11. Comparison of various designs used for computing unit skin friction in sands.
Figure 6-11. Comparison of various designs used for computing unit skin friction in sands.













End Bearing in Clays


0 10 20 30 40 50 60
- -- No Data zone SPT N Values

-*-SPT97, Concrete Piles --- SPT97, Steel Piles -e- Large Diameter Piles (steel/concrete)


Figure 6-12. Comparison of various designs used for computing unit end bearing in clays.













END BEARING IN SILTS


35


30


25
o-

20 -




10

15


0
0 10 20 30 40 50 60 70
- No Data zone SPT N Values

-- SPT97, Concrete Piles -- SPT97, Steel Piles -- Large Diameter Pile (steel/concrete)

Figure 6-13. Comparison of various designs used for computing unit end bearing in silts.
















End Bearing in Sands


70


60


LL 50


4 40






0 20


10




0 10 20 30 40 50 60 70
--- -- No Data zone SPT N Values


-- SPT97, Concrete Piles -- SPT97, Steel Piles -- Large Diameter Pile (steel/concrete)

Figure 6-14. Comparison of various designs used for computing unit end bearing in sands.














Unit Skin Friction Curves


F'


1.4

LL 1.2
C1,
F-
- 1
0
c,
*C 0.8
LI.
U-

S0.6

-0.4
c',
3 0.4


SPT N Values

-- Concrete, Clay -W- Steel, Clay Concrete, Silts Concrete, Sands --- Steel, Sands

Figure 6-15. Comparison of unit skin friction vs. SPT N values, for various soil types, and pile materials, in case of cylinder piles.


1/ ^^'


~*IY














Unit End Bearing Curves for Cylinder Piles


30


125

30
C" 25





15
C

S10


5


0
0 10 20 30 40 50 60 7(
SPT N Values

Clays -W- Silts -A- Sands

Figure 6-16. Comparison of unit end bearing vs. SPT N values, for various soils, in case of cylinder piles.













CHAPTER 7
LOAD AND RESISTANCE FATOR DESIGN (LRFD)

For many years, allowable stress design (ASD) was used for the design of bridges,

building and other structures. In the 1970's, the American Association of State Highway

and Transportation Officials (AASHTO) introduced a new design procedure for bridge

superstructures. The design procedure was known as load factor design (LFD). It

revolutionized the design of bridge superstructure by allowing the structural engineer to

set different factors for different types of loads on the bridge. But, when the structural

engineer designed the superstructure, he/she had to keep track of two different sets of

loads. One set for the superstructure, which required factored loads, and one set for the

foundation design, which was still using ASD method. In the 1980's, resistance factors

were introduced into LFD. This created a new design method known as load and

resistance factor design (LRFD).

An important goal of driven pile design is to prevent a limit state from being

reached. This goal is implied by both the traditional "allowable stress design"--ASD

method (by means of the safety factor Fs) and the "load and resistance factor design"--

LRFD method (by means of the load factors yi and the resistance factor D). However,

other goals that must be considered and balanced in the overall design are function,

appearance, and economy. The LRFD, which is presented in section 7-2, has more

advantages over the ASD, which is presented in section 7-1, in achieving these goals.









7.1 Allowable Stress Design

Before the introduction of LRFD, ASD was used for all designs. ASD works by

reducing the calculated or estimated resistances by a global factor of safety, resulting in a

maximum design load. The estimated loads (or stresses) Qi are restricted as shown

bellow:

R
S> EQI Eq.7-1
Fs

Where: Rn = Nominal resistance,

Fs = Factor of safety--usually from 2.0 to 4.0, and

XQi = Load effect (dead, live and environmental loads).

For pile foundations, the equation can be rewritten as:

Rn/ Fs = (R + Rp)/ Fs > QD + QL Eq.7-2

Where: QD = Dead load,

QL = Live load,

Rs = Side resistance, and

Rp = Tip resistance.

7.2 Load Resistance Factor Design

The LRFD specifications as approved by AASHTO (AASHTO, 1996/2000)

recommend the use of load factors to account for uncertainty in the loads, and resistance

factors for the uncertainty in the material resistances. This safety criterion can be written

as:

ORn > qY Yi Qi Eq.7-3

Where: Rn = Nominal resistance,









r = Load modifier to account for effects of ductility, redundancy and operational

importance. The value of r usually ranges from 0.95 to 1.00. In this thesis, r =

1.00 is used.

Qi = Load effect.

Yi = Load factor. Based on current AASHTO recommendation, the following

factors are used:

YD = 1.25 for dead load,

YL = 1.75 for live load,

D = Resistance factor--Usually ranges from 0.3 to 0.8.

For driven piles, we have

ORn > 1 1.25 QD+ 1.75 QL Eq.7-4

If different resistance factors are used for tip and side resistance, then

OsRs + (OpRp > 1.25 QD + 1.75 QL Eq.7-5

Where: Rs = Side resistance,

Rp = Tip resistance, and

Os; (p= Resistance factors for side and tip resistance,

respectively.

The LRFD approach has the following advantages:

* It accounts for variability in both resistance and load. (In ASD, no consideration is
given to the fact that different loads have different levels of uncertainty). For
example, the dead load can be estimated with a high degree of accuracy; therefore,
it has a lower factor (1.25) in LRFD.

* It achieves relatively uniform levels of safety based on the strength of soil and rock
for different limit states and foundation types.









* It provides more consistent levels of safety in the superstructure and substructure as
both are designed using the same loads for known probabilities of failure. In ASD,
selection of a factor of safety is subjective, and does not provide a measure of
reliability in terms of probability of failure.

* Using load and resistance factors provided in the code, no complex probability and
statistical analysis is required.

The limitations of the LRFD approach include:

* Implementation requires a change in design procedures for engineers accustomed to
ASD.

* Resistance factors vary with design methods and are not constant.

* The most rigorous method for developing and adjusting resistance factors to meet
individual situations requires the availability of statistical data and probabilistic
design algorithms.

7.3 Calibration of Resistance factor for LRFD

Calibration of resistance factors is defined as the process of finding the D values to

achieve a required target probability of survival. There are three approaches that have

traditionally been used in the LRFD calibration.

7.3.1 Engineering Judgment

The D factor is assigned empirically by engineering judgment, and it is to be

adjusted by the past and future performance of foundations designed using that factor.

7.3.2 Fitting ASD to LRFD

The resistance factor D is fitted through the factor of safety Fs and other load

parameters by equating equation 7-2 and equation 7-4:


YD QD YL

QD
LQ
= --Eq.7-6
]jQD+1









If yD = 1.25 and YL = 1.75 as recommended by AASHTO and if QD/QL is from 1.0

to 4.0 then

1.50 to 1.35 Eq
(D = Eq.7-7


Equation 7-7 is the basic calibration equation for calibrating the LRFD resistance

factor by fitting with ASD.

7.3.3 Reliability Calibration

There are three levels of probabilistic design (Withiam et al., 1997). The fully

probabilistic method (i.e.,, level III) is the most complex and requires knowledge of the

probability distributions of each random variable and correlations between the variables.

The level I method is referred to as the mean value first order second moment (MV

FOSM) method.

The level II method, which is recommended by AASHTO and FHWA, is referred

to as the advanced first order second moment method (A FOSM). The equations

presented in this section are based on level II method, adapted from the FHWA

workbook (Withiam et al., 1997).

7.3.3.1 Resistance bias factor

The resistance bias factor is defined as:

R
T Eq.7-8


Where: Rm = Measured Resistance,

Rn = Predicted (Nominal) Resistance

The mean, standard deviation and coefficient of variation of the set of bias data R, are











Mean: R Eq.7-9



Standard Deviation: O- = Eq.7-10
N-1


Coefficient of Variation: COVR = -R Eq.7-11
AR

The mean of the bias factor represents a trend between what is predicted and what

is measured.

7.3.3.2 Reliability index 3

Figure 7-1 presents the graph of the probability distribution function of


g= n( ) Eq.7-12


R = pile capacity, which is (D Rn),

Q = load effect, which is (iQD QD + D QL QL)

When the pile capacity R is smaller than the load effect Q, then g < 0, represented

by the shaded region in figure 7-1. This shaded zone is also referred to as the probability

of failure, pf. In pile foundation design, a range from 0.1% to 10.0% is used. This range

is high because piles are usually used in groups, failure of one pile does not necessarily

imply that the pile group will fail.

The reliability index 3 is defined as the ratio between the lognormal mean, g and

the lognormal standard deviation, ,g,.

g
S= or g = P*g Eq.7-13
R'




















AREA = P -- ,



0 g ln(RJQ) g= tn(IQ)
Figure 7-1. Failure region and the reliability 3

In Figure 7-1, if 3 is higher, then P3*g is higher, the graph is stretched further to the

right and the failure region, pf, will be smaller.

Rosenblueth and Esteva, 1972 (cited in Withiam et al., 1997) developed the

following simple equation relating pf with 3:

pf = 460 e-4.3 (2 < P < 6) Eq.7-14

For civil engineering project, 3 usually ranges from 2.0 to 4.0. However, due to the

redundancy of pile groups, AASHTO and FHWA recommend using 3 from 2.0 to 2.5 for

pile foundations (cited in Withiam et al., 1997), and it is called the target reliability index

PT.

Table 7-1. Relationship between probability of failure and reliability index for lognormal
distribution (Rosenblueth and Esteva, 1972).


Reliability Probability of
Index, 0 failure, Pf
2.25 .29E-1
2.5 .99E-2
3.0 1.15E-3
3.5 1.34E-4
4.0 1.56E-5
4.5 1.82E-6


Reliability Index, 0 Probability of
failure, Pf
1E-1 1.96
1E-2 2.5
1E-3 3.03
1E-4 3.57
1E-5 4.1
1E-6 4.64