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Local sediment scour model tests for the Royal Park Bridge piers

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Title:
Local sediment scour model tests for the Royal Park Bridge piers
Series Title:
Local sediment scour model tests for the Royal Park Bridge piers
Creator:
Sheppard, D. Max
Place of Publication:
Gainesville, Fla.
Publisher:
Coastal & Oceanographic Engineering Dept. of Civil & Coastal Engineering, University of Florida
Language:
English

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University of Florida
Holding Location:
University of Florida
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All applicable rights reserved by the source institution and holding location.

Full Text
UFL/COEL-99/024

FINAL REPORT
LOCAL SEDIMENT SCOUR MODEL TESTS FOR THE ROYAL PARK BRIDGE PIERS
by
D. Max Sheppard University'of Florida Gainesville, Florida and
Mufeed Odeb
U.S. Geological Survey T u r n r F all M a s c u e t
December 1999
Submitted to: E.C. Driver and Associates and
Florida Department of Transportation District IV
Coastal & oceanographic Engineering Program
Department of Civil & Coastal Engineering __ 4
433 Wel Hall 0 P.O.Box 116590 0 Gainesville, Florida 32611-6.
UNIVERSITY OF 'FLORIDA




UFL/COEL -99/024

FINAL REPORT LOCAL SEDIMENT SCOUR MODEL TESTS FOR THE ROYAL PARK BRIDGE PIERS
by
D. Max Sheppard University of Florida Gainesville, Florida and

Mufeed Odeh U.S. Geological Survey Turner Falls, Massachusetts
December 1999
Submitted to:
E.C. Driver and Associates and
Florida Department of Transportation District IV




FINAL REPORT

LOCAL SEDIMENT SCOUR MODEL TESTS FOR THE
ROYAL PARK BRIDGE PIERS
SUBMITTED TO:
E.C. DRIVER AND ASSOCIATES

FLORIDA

AND
DEPARTMENT OF TRANSPORTATION
DISTRICT IV

CONTRACT NO. 03-54297-00
UF NO. 4910451135412
SUBMITTED BY:
D. MAX SHEPPARD
UNIVERSITY OF FLORIDA GAINESVILLE, FLORIDA
AND
MUFEED ODEH
U.S. GEOLOGICAL SURVEY
TURNERS FALLS, MASSACHUSETTS

DECEMBER 1999




EXECUTATIVE
SUMMARY
Two small scale (large model) local sediment scour tests were performed on a model of the two largest and most complex piers for the Royal Park Replacement Bridge. This bridge is located on Royal Palm Way at the crossing of the ICCW (intracoastal waterway) in West Palm Beach, Florida. The model tests were conducted by the University of Florida and the USGS Laboratory in the USGS Laboratory in Turners Falls, Massachusetts. All tests were conducted at velocities just below critical velocity (i.e. just below the velocity needed to initiate sediment movement on the flat bed upstream of the structure) for the uniform diameter, 0.8 mm sand used in the flume. The local scour depths for the prototype pier, were computed by two different methods from the measured model scour depths. The "Conventional Method" assumes that the scour depth at transition from clearwater to live bed scour conditions in the model study should be multiplied by the geometric scale of the model to obtain the prototype scour depth. A second method referred to here as Sheppard's Method takes into consideration the fact that the sediment in the model test is not scaled properly and that the prototype scour depth depends on the design flow velocity. The model parameters with the measured and corrected (corrected for test velocity being slightly less than critical) scour depths are given in Table ES-1. The prototype scour depths for four different velocities believed to span 100 and 500 year return interval flows are given in Table ES-2.
Table ES-1. Model Test Conditions and Results Water Depth Critical Sediment Test Measured Corrected
Depth, Average Velocity, Diameter, Duration Scour Scour
Test Pier Yo Velocity, U U, D50 (hr) Depth, Depth
(m) (m/s) (m/s) (mm) d,, U/U:=I
(m) (m)
I No. 4 0.45 0.31 0.38 0.80 143.00 0.37 0.50
2 No. 5 0.67 0.33 0.40 0.80 95.30 0.43 0.61
Table ES-2. Prototype local scour depths for a range of velocities using two different methods.
Design Design Prototype Local Scour Depth
Pier Water Depth Velocity (m)
(m) (m/s) Conventional Method Sheppard's Method
Less Than 100 Year
No. 4 6.75 0.45 2.69
No. 5 10.47 0.45 3.80
100 YearI
No. 4 6.75 0.50 1 Y 2.81
No. 5 10.47 0.49 3.90
500 Year'
No. 4 8.09 0.56 9.99 3.29
No. 5 11.81 0.65 12.04 4.64
Greater Than 500 Year
No. 4 8.09 1.00 1 4.33
No. 5 11.81 1.00 5.61
Greater Than 500 Year
No. 4 8.09 I 2.00 I 6.73
No. 5 11.81 2.00 8.37
1 Water depths and flow velocities provided by E.C. Driver




LOCAL SEDIMENT SCOUR MODEL TESTS FOR THE ROYAL PARK BRIDGE PIERS
INTRODUCTION:
The Royal Park Bridge at the Royal Palm Boulevard crossing of the ICCW in West Palm Beach, (Palm Beach County) Florida is being replaced. This bridge which connects the barrier island of Palm Beach to the mainland is located approximately 5 miles south of Lake Worth (Palm Beach) Inlet. Since this is a bascule bridge the main piers are quite large and have numerous piles in their foundation, some of which are battered. The purpose of the model tests reported here is to provide a basis for the establishment of design scour depths for the two main piers. Since the two main piers (Piers 4 and 5) at the channel are similar only one model was constructed. A model of Pier 5 was used since it will produce the largest scour. The predicted flow conditions are different for the two piers and thus were different in the flume tests. The model pier size was made as large as possible for the width of the flume to minimize scale effects. The width of the flume at the USGS Laboratory is 20 ft. The limit of the "effective width" of structures for which local scour tests can be conducted in this flume is approximately 3 ft.
EXPERIMENTAL PROCEDURE:
Both model tests were conducted in the USGS Laboratory flume in Turners Falls,
Massachusetts. The flume is 126 ft long x 20 ft wide x 21 ft deep. The flume contained a 6 ft deep layer of sediment as shown in Figures I and 2. To minimize the amount of near uniform diameter sediment needed for the tests a 5 ft layer of filler material (pea gravel) was used outside of the test area, as shown in Figures 1 and 2. Local scour tests are normally performed in near uniform diameter sediment since the greatest scour depths occur under these conditions. The sediment used for these tests was quartz sand with a median grain size, D50 of 0.8 mm. and a
r 84 = 13.
D6
The sediment in the entire flume was leveled (with a transit) and compacted. An acoustic depthmeasuring instrument on a traversing mechanism was installed adjacent to the pier for both tests along with an underwater video camera that was used for the Pier No. 5 test. Two electromagnetic current meters were installed upstream and on either side of the model.
Water for the flume comes from a power plant reservoir on the Connecticut River
adjacent to the Laboratory. The water is discharged from the flume into the river downstream of control structures where the water level is at least 30 ft below the reservoir elevation.
The scour depth was monitored throughout each test to insure that the duration of the test was sufficient to achieve equilibrium scour depths. One pier design and two different flow conditions were tested. The tasks performed are outlined below:




Task 1. A scale model of the proposed Bascule Pier No. 5 was constructed. Two views of the
pier prior to installation in the flume are shown in Figures 3 and 4. The geometric scale
used was 1: 19.9.
Task 2. Sediment in the test area was excavated and the model pier was installed. The sediment
was compacted at approximately Ift intervals to insure the proper sediment porosity.
See the photograph in Figure A2. An acoustic transponder array on a traversing
mechanism was installed near the structure (for both tests) for the purpose of
monitoring the scour depth as a function of time (however, the transponders did not
work correctly for the Pier No. 5 test). Video cameras in streamlined underwater
housings were set up for periodic submersion to obtain readings of scour depths at
specific piles where vertical scales attached.
Task 3. The flume was filled with water and allowed to stand for approximately 12 hours. It
was then drained slowly and the bed compacted once again. This procedure was used
to insure that there were no voids in the sediment near the structure.
Task 3. The first test was performed. The test procedure was as follows:
a. Video and still photography were used to document the initial conditions.
b. The flume was filled, being careful not to generate scour during the fill process.
Water was allowed to stand at the level of the weir until air trapped in the bed had
escaped.
C. The flow and instrumentation were started. Scour depths were monitored at
specified time intervals throughout the test with an underwater video camera (and
in the Pier No. 4 test, acoustic transponders).
e. Periodic plots of scour depth versus time were made in order to establish the time
when the local scour depth reached equilibrium.
f. The test was stopped and the flume drained.
g. Point gauge measurements of scour hole and surrounding area were made. Still
and video images of the scour hole were made.
Task 4. The data was reduced and analyzed.
Task 5. Tasks 2 4 were repeated for a second flow condition as stated in Task 1. Even though
the same structure was used in the second test the sediment near the structure had to be removed and the pier positioned to a new elevation. Since a different water depth was
used in the second test the downstream flow control weir also had to be changed.
Test Procedure:
The model was designed and constructed at the USGS Laboratory according to the prototype pier drawings provided by E. C. Driver and Associates. As stated above the geometric scale for the model (1: 19.9) was controlled by the width of the flume (20 ft). The sediment in the test section was excavated and the model installed and bolted to the floor of the flume. Sediment was placed around the structure in 1 ft layers and compacted using a commercial (diesel powered) sediment compactor on each layer. (see the photograph in Figure A2). The flume was filled slowly to the depth of the downstream flow control weir and allowed to stand overnight. This allowed further




compaction and the reduction of voids in the sediment. The flume was then drained and the sediment compacted once again. Next the flume was filled slowly and allowed to sit for several hours until the air in the sediment had escaped. The gates to the reservoir were then opened and the test started. The flow velocity, water depth and temperature were monitored throughout the experiment. Once the scour depth had reached near equilibrium (no change in depth over a 12hour period) the test was stopped and the flume drained through openings at three locations in the flume floor. After photographs of the scour hole were taken the point gauge apparatus was installed and the bathymetry in the region surrounding the model surveyed. Sediment near the pier was excavated and the pier repositioned for the second test. The test procedure described above was then repeated.
Test Results:
The sediment and flow conditions and measured maximum local scour depths for the two tests are presented in Table 1. Photographs of the flume and tests, including before and after (test) shots of the piers, are given in Appendix A. Test summary sheets and contour plots of the scoured bed elevation (using point gauge measurements) are given in Appendix B along with scour time history plots for the two tests. The time history plots are for points near, but not at, the points of maximum scour. It is obvious from these plots that the scour depth is very near equilibrium values at the end of the tests.
Table 1. Model sediment and flow conditions and measured maximum scour depths
Water Depth Critical Sediment Test Measured Corrected
Depth, Average Velocity, Diameter, Duration Scour Scour
Test Pier yo Velocity, Uc D50 (hr) Depth, Depth
(in) U (mis) (mmI~) dse UfUC=1I
______(mis) _____ _(in) (in)
1 No. 4 10.45 10.31 0.3 8 0.80 143.00 0.37 0.50
2 No. 5 0.67 0.33 0.40 0.80 95.30 0.43 0.61
Data Analysis:
The local scour depths for the prototype structures are computed using two different
methods. Both methods start by adjusting the measured scour depth to the equilibrium value that would occur at transition from clearwater to live bed scour conditions in the model. In general this requires two corrections, one for the duration of the test and one for the test velocity being less than the critical value. The resulting scour depth is the value that would occur if the test were run at the critical (transition) velocity until the scour depth reached an equilibrium value.
The Conventional Method takes the model equilibrium scour depth and multiplies it by the geometric scale to obtain the prototype scour depth. It should be noted that prototype scour depths obtained by this method will vary depending on the sediment size used in the model study. That is, if a different sediment size was used in the model test and U/IJc was kept the same, the measured and therefore the predicted prototype scour depth would be different. This method is also independent of prototype design velocities.




The second method utilizes the local scour prediction equations developed by Sheppard (see Appendices C and D) to obtain the prototype scour depths from the model results and takes into consideration the fact that the sediment is not properly scaled in the model. This method will predict the same prototype scour depth regardless of the sediment size used in the model tests and also accounts for the magnitude of the design velocities.
To illustrate the two procedures a sample calculation for one of the piers is presented below:
Pier No. 5
Table 2. Model Test Conditions and Results.
Water Depth Critical Sediment Test Measured Corrected
Depth, yo Average Velocity Diameter, Duration Scour Depth Scour Depth
(m) Velocity, U UC D50 (mm) (hr) (m) (m)
(m/s) (m/s)
0.67 0.33 0.40 0.80 95.30 0.43 0.61
The duration of this test was 95.3 hours. A plot of bed elevation versus time (at a location near the point of maximum scour) is shown on page B-12 in Appendix B. Based on this plot it is assumed that the scour depth has reached its equilibrium value, therefore a correction for scour depth maturity is not necessary. The correction to the scour depth for the test velocity being slightly less than transition (from clearwater to live bed) is computed next. The (depth averaged) velocity divided by the (depth averaged) critical velocity, U/Uc, for this test was 0.83. This correction is made using Equation 1 on page C-2 in Appendix C.
dse
b U 0 [-2.5(10)- 14
ds !L=0.825 [2.5(0.825)-1.0]=
ds at =1.0 dse( at -cc=0.825 1.412 = (0.43 m)(1.412) = 0.605 m.
where
U depth averaged velocity upstream of pier and
U: critical depth average velocity.




Conventional Method

To obtain the prototype scour depth for this pier using the Conventional Method the
U
model scour depth at -- = 1 is multiplied by the geometric scale (1:19.9 in this case).
Uc
d (prototype) = Sg d.(model) = 19.9*.605 = 12.04 i
Sheppard's Method
This method requires several steps but as stated above takes into consideration the fact that the sediment is not scaled in the model study. This has a significant impact on the predicted prototype scour depths as can be seen in the following calculations.
First the effective diameter of the model pier, Din, must be computed using Equation 5 on page D-2 in Appendix D. For this situation, the maximum scour depth that can be attained by any circular pile in the specified sediment and water depth is 0.57 m. The measured scour depth corrected to U/U, = 1 however is 0.61 m. This means that there is no circular pile that will create a scour depth as great as 0.61 m in the same sediment, water depth and with the same flow velocity. This situation is discussed in more detail in Appendix D. In this case the reference pile shape must be something other than circular. The D* is then the diameter of pile with a shape coefficient, KI that would experience the same scour as the model pier under the same sediment and flow conditions. The value of K can be obtained by dividing the measured scour depth (corrected) by the maximum scour depth for a circular pile (See Appendix D for the reasoning behind this calculation).
0.605
K1 0.570 -1.06.
The magnitude of the effective diameter, D*, can then be obtained by solving Equation 9 in
Appendix D for Dm, i.e. solving the following equation:
dse (at =1)= 0.61 =K1 D co[c1 -1.0]
Uc
= 1.06 Dm c[c1-1.0]
Solving this equation yields
Dm = 0.702 m.
That is, a 0.702 m diameter pile with a shape coefficient of 1.06 will experience the same scour depth as the model pier when subjected to the same sediment and flow conditions.




The effective diameter of the prototype pier is simply the geometric scale times the model effective diameter,
D* Effective Diameter of Prototype Pier = S D = 19.9 0.702 m = 13.97 m.
At this bridge site the prototype sediment is primarily fine sand with a
D50(prototype) = 0.2 mm. Using this value the prototype pier scour depth can be computed for any flow velocity using Equations 1-9 in Appendix C. If the design velocity is in the live bed scour range, as is usually the case, then the velocity at the point where the bed flattens or "planes out", Ulp, (the velocity at which the scour depth reaches its peak in the live bed scour range) must be estimated. This can be done using Tables 1-4 in Appendix C. For this situation, Ulp = 7.86 m/s.
Pier No. 5
For a 500 year flow velocity of .65 m/s, and water depth of 11.81 m the prototype scour depth is:
ds U P-U
S= KI c2 Ip +c3
DD
-
k tanh 1j{ -0.31+0.051exp loglO, 0.75 0
(13.97 m)loglo D104
--1
m___ 0.75 I =- 2
k-tanh(llm8)-[0.31+0.051exp(llO104)+ logl0(104 =0.26
k- 2.4 tanh 11.81 m
-2 G13.97 m 0.26 (2.4)(0.689)_.07
c2 = =- -0.07
IU 7.86 m/s 1.
Uc 0.36 m/s
c3 = 2.4tanhY-~= (2.4) tanh 11.81 = (2.4)(0.689)=1.65
Dp (13.97 m)
dse c(Ulpp-U+c (0077.86 m/s-0.65 m/s + 1.65 0.248
K1D- c2 U + c3= (-0.07) 0.36 rn/s +
KID* Uc 0.36 m/s




dse = (13.97 m)(1.06)(0.248) = 4.64 m

d U
These results are shown in the following plot of e vs Dp Uc

dse
KID'

2.39 0.30 0.27

- --- -II I

0.4 1.0

UD 1.4
Uc
U
Uc

Ulp 21.2 Uc

The effective diameters of the two pier configurations are given in Table 3 along with prototype critical velocities, Uc, and velocities at maximum live bed scour, Ulp.
Table 3. Model and prototype effective diameters and prototype critical velocities and velocities
at the live bed peak.
Pier Model Geometric Reference Prototype Prototype Prototype
Effective Scale Pile Effective Critical Live Bed Peak
Diameter Shape Diameter Velocity Velocity Ulp3
(m) Factor (m) (m/s) (m/s)
K2
No. 4 0.49 19.9 1.11 9.72 0.34 6.55
No. 5 0.70 19.9 1.06 13.97 0.36 7.86




Using the procedures outlined above the prototype scour depths for both flow situations were computed for five different design velocities spanning the 50 and 500 year return interval velocities specified by E. C. Driver and Associates. Should the design velocities change during the design process the local scour depths can be interpolated from the values given in Table 4.
Table 4. Prototype local scour depths for a range of design velocities using two different
methods.
Design Design Prototype Local Scour Depth
Pier Water Depth Velocity (in)
(in) (mis) Conventional Method I Sheppard's Method 3
Less Than 100 Year
No. 4 I 6.75 I 0.45 I 2.69
No. 5 10.47 0.45 3.80
100 Year'
No. 4 I 6.75 I 0.50 I 2.81
No. 5 10.47 0.49 3.90
500 Year'
No. 4 8.09= 0.56 9.99 3.29
No. 5 11.81 0.65 +12.04 4.64
Greater Than 500 Year
No. 4 I 8.09 I 1.00 II4.33
No. 5 11.81 1.00 5.61
Greater Than 500 Year
No. 4 I 8.09 I 2.00 I 6.73
No.5 11.81 2.00 8.37
'Water depths and flow velocities provided by E.C. Driver
Summary:
The results from the model tests are presented in Table 1. The projected prototype local scour depths computed by two different methods are given in Table 4. The method referred to here as the Conventional Method for obtaining prototype scour depths from model test data is one of the more common methods used by laboratories conducting local scour model studies for bridge piers. The second method used to estimate the prototype local scour depths is based on Sheppard's equations which were first published in 1995 [Sheppard, et al. (1995)] and later extended to include the live bed scour range [Sheppard (1999)]. Recent laboratory experiments with near prototype scale circular piles verify these equations in: the clearwater scour range. Additional live bed tests are planned for the spring of 2000 by the authors of this report, for the purpose of testing/verifying these equations in the live bed range. It is the opinion of the authors that even though more data is needed in the live bed range there is more evidence to support using this method than there is for using the Conventional Method.




Flow Intake from Reservoir

NOT TO SCALE
All dimensions in feet

Flow Discharge To Connecticut River

Figure 1. Plan view of the large flume in the USGS Conte Hydraulics Laboratory in Turners Falls, Massachusetts. Cross-sections AA
and BB are shown in Figure 2.




20

Water
Test Sediment

Section A-

NOT TO SCALE All dimensions in feet

T

Filter material Base Sediment Test Sediment Base Sediment

Section BFigure 2. Cross-sections of the large flume in the USGS Conte Hydraulics Laboratory in Turners Falls, Massachusetts.




Figure 3. Photograph of the front of Pier No. 5. Geometric scale is 1: 19.9.

Figure 4. Photograph of the side of Pier No. 5. Geometric scale is 1: 19.9.




Acknowledgments:

The authors would like to acknowledge the work of Research Engineers John Norieka, and Tom Glasser for designing the models, model installation, conducting the tests and reducing the data. A special thanks also to Stephen Walk for assisting with the instrumentation and data gathering and to Phil Rocasah for constructing the models and assisting with their installation.
References:
Ettema R. (1980), "Scour at Bridge Piers", Ph.D. Dissertation, Auckland University, Auckland,
New Zealand, Report No. 216.
Chiew, Y.M. (1984), "Local Scour at Bridge Piers", School of Engineering Report No. 355,
Department of Civil Engineering, Auckland University, Auckland, New Zealand.
Sheppard, D. Max (1995), Budianto Ontowirjo and Gang Zhao, "Local Scour Near Single Piles in Steady
Currents," presented at and published in the proceedings of the 1st Hydraulics Engineering Conf., San
Antonio TX, August 1995.
Sheppard, D. Max (1999), "Conditions of Maximum Local Scour," Compendium of Scour Papers from
ASCE Water Resources Conferences, Eds. E.V. Richardson and P.F. Lagasse, 1999.
Snamenskaya, N.S. (1969), "Morphological Principle of Modelling of River-Bed Process",
International Association for Hydraulic Research, 195-200.




Figure Al. Photograph of the flume at the USGS Laboratory in Turners Falls, MA during a
local scour test.
A-1




Figure A2. Photograph of sediment being compacted in the flume.
A-2




Figure A3. Photograph of Pier No. 4 prior to filling the flume and running Test Number 1.
Geometric scale 1:19.9.
A-3




Figure A4. Photograph of Pier No. 4 and scour hole after Test Number 1. Geometric scale
1:19.9.
A-4




Figure A5. Photograph of Pier No. 4 and scour hole after Test Number 1. Geometric scale
1:19.9.
A-5




Figure A6. Photograph of Pier No. 4 and scour hole after Test Number 1. Geometric scale
1:19.9.
A-6




Figure AT Photograph of Pier No. 5 prior to filling flume and running Test Number 2.
Geometric scale 1: 19.9.

A-7




Figure A8.

Photograph of Pier No. 5 and scour hole after Test Number 2. Geometric scale 1:19.9.

A-8




Figure A9. Photograph of Pier No. 5 and scour hole after Test Number 2. Geometric scale
1:19.9.
A-9




Figure A1O. Photograph of Pier No. 5 and scour hole after Test Number 2. Geometric scale
1:19.9.

A-10




APPENDIX B
LOCAL SCOUR MODEL TEST RESULTS




Sediment Scour Experiment Summary for Pier No. 4
Experiment: Pier No. 4 Laboratory: USGS-BRD Lab Scale: 1/19.9 Date: 11/7/99 Person completing form: Tom Glasser
Persons performing experiment: Tom Glasser John Noreika Mufeed Odeh
Date(s) and times of Experiment: From 11:50 PM on 10/08/99 to 7:30 AM on 10/14/99 Duration of test (hours): 143 Structure: Royal Park Pier #4 model




Sketch of structure: All Dimensions are in Meters




Sediment:
Type: Quartz sand
D50 (mm): 0.8
cy: 1.25
ps (Kg/m3): 2650
Flow:
Velocity, U:
Velocity meters Left side facing upstream West
Average velocity (m/s):0.374
Velocity range (m/s): From 0.333 to 0.408
Velocity meters Right side facing upstream East
Average velocity (m/s): 0.379
Velocity range (m/s): From 0.349 to 0.398
Channel average velocity from weir (m/s): 0.314
Critical (sediment) velocity, U. (m/s):0.375
Water depth, yo:
Average water depth (m): 0.452
Depth range (m): From 0.443 To 0.461
Water temperature
Average water temperature (degrees C): 13.3
Temperature range (degrees C): From 13.1 To 13.5
Local Equilibrium Scour Depth, dse: Maximum depth from acoustic pingers (m): 0.248
Maximum depth from video (m): NA
Maximum depth from point gauge (m): 0.366
Maximum scour depth (m): 0.366
Dimensionless parameters: D* = 0.49 m Shape Coefficient: K2 = 1.11

ds/D* I yo/D* U/Uc D5o/D*
0.747 0.922 0.84 0.0016




Computer Data Files
Acoustic Raw Data Folder"M4 Pinger Data"
Acoustic Processed Data M4 filtered Pinger data.xls
Point Gage Data
Data file M4 Grid Data Metric 11-15-99.dat Grid file M4 Grid Data Metric 11-15-99.grd
Contour file M4 contour Plot modified 11-15 Metric.srf
Video Processed Data NA
Velocity and Water Depth Data M4 Velocity and Water Surface Elevation.xls
Other
Discussion:
Was run with the use of the pingers, but was not able to use the cameras because the traversing mechanism was in the way. A value of 5 was used for the relative roughness in the Ucrit calculation. The depth reading was not correct. Therefore a new calibration was used after the experiment was performed. The new calibration is in the run folder.
Pier #4 Summary Data
0.4 0.5
IN& _0.48

- 0.25
S0.2
8D

- -
0.46 0.44
0.42 E
0.4
0.38

* West Vel
m East Vel Water Level

t 0.36

0.05

I I i i 11!1 1 I

0 20 40 60 80
Time (hrs)

100 120 140 160

0.3




M4 Pier Scour Test

0.5 1 1.5 2 2.5 3 3.5 4 4.5

Maximum Scour Depth = 0.366 meters




M4 Filtered Pinger Data for 10-8 to 10-14
-- Ping 1 4 Pingw 2
O Pin 3
A Ping 4
-i
0
I I I
0 40 80 120 160
Time her's ) The Pinger data was taken directly off of the center of the structure. The pinger was set off of the front of the structure by about 4 inches.




Sediment Scour Experiment Summary For Pier No. 5
Experiment: Pier No. 5 Laboratory: USGS-BRD Lab Date: 11/7/99 Person completing form: Tom Glasser
Persons performing experiment: Tom Glasser John Noreika Mufeed Odeh
Date(s) and times of Experiment: From 12:54 PM on 10/21/99 to 9:00 AM on 10/25/99 Duration of test (hours): 95.3 Structure: Royal Park Pier #5 model




Sketch of structure: All dimensions are in Meters.

3D View

Water Surface

Section View

SBattered Plan View t1 .724

,03,38 .038TP.
U ] E H1 0 11
HUE] D H U] EDUCE, T h.
-O EDED

HE
HE
* H
H
HE

OHOMOR OMOHOW OU EDEO
OMOHOM OHOWOM DEDEDE ]

.05B 4. 124R




Sediment:
Type: Quartz sand
D50 (mm): 0.8
a : 1.25
Ps (Kg/m3): 2650
Flow:
Velocity, U:
Velocity meters Left side facing upstream West
Average velocity (m/s):Meter was not working
Velocity range (m/s): From NA to NA
Velocity meters Right side facing upstream East
Average velocity (m/s): 0.352
Velocity range (m/s): From 0.454 to 0.300
Channel average velocity from weir (m/s): 0.328
Critical (sediment) velocity, Uc (m/s):0.396
Water depth, yo :
Average water depth (m): 0.668
Depth range (m): From 0.660 To 0.675
Water temperature
Average water temperature (degrees C): 10.85
Temperature range (degrees C): From 10.4 To 11.3
Local Equilibrium Scour Depth, dse: Maximum depth from acoustic pingers (m): NA
Maximum depth from video (m): 0.430
Maximum depth from point gauge (m): 0.432
Maximum scour depth (m): 0.432
Dimensionless parameters: D* = 0.70 Shape Coefficient K2 = 1.06

I d/D I yoD* U/UC D50/D*
0.617 0.954 0.83 0.0011




Computer Data Files
Acoustic Raw Data NA
Acoustic Processed Data NA
Point Gage Data
Data file M5 Grid Data Metric 11-15-99.dat Grid file M5 Grid Data Metric 1 1-15-99.grd
Contour file M5 Contour Plot metric 11-15-99.srf
Video Processed Data M5 Time rate of scour.xls
Velocity and Water Depth Data M5 Summary of Velocities.xls
Other
Discussion:
This test was run in ideal weather and the water was very clear. There was still black stuff on the sand, but not as much as usual. A value of 5 was used as a roughness factor when calculating the Ucrit. The West velocity meter was not functioning.
Pier #5 Summary Data
0.4 0.59
0.35 0.58
--0.57
o,0.25 M-7
0 56
.2 *East Vel
0.55
Water Level
0.2
0.54
~0.53
0.1
-0.52
0.05 0.51
0 -0.5
0 10 20 30 40 50 60 70 80 90 100
Time (hr$)

B-10




0.5 1 1.5 2 2.5 3 3.5 4.5

Maximum Scour Depth =0.432 meters

B-11

Pier #5 Contour Plot




Pier #5 Time Rate

Pier #1 Pier #2 Pier #3

0 10 20 30 40 50 60
Time (hrs)
Water Surface

Bed Pier #3

70 80 90 100
Pier #1

Pier #2

B-12

SH




APPENDIX C
COMPUTATION OF LOCAL SCOUR DEPTH FOR A CIRCULAR PILE




Computation of Local Scour at a Single Circular Pile D. Max Sheppard
December 1999
The equilibrium local scour depth at a single circular pile can be computed as follows. Refer to the definition sketch in Figure 1. For design purposes the scour depth is computed by one of three straight-line equations depending on the value of
-U- If the velocity where the scour depth is desired is in the clearwater scour Uc
range (i.e. 0.4 < U < 1.0) the scour is computed using the equation for the line
Uc
between points 1 and 2 in the sketch. For velocities in the live bed scour range
1.0 < U< UIP, (where Ulp is the velocity at the live bed peak scour depth) the
Uc UPth
equation for the line between points 2 and 3 is used. For J-c > UlP the Ud U
dimensionless scour depth is constant at the value at point 3.

d se/b

00.4 1.0

Ud/Uc U ip/U C

U/UC
Figure 1. Definition sketch. Nondimensional equilibrium, local scour depth versus
nondimensional depth averaged velocity.




Figure 2. Definition sketch of circular pile showing flow, sediment and structure parameters. The critical depth averaged velocity, Uc, must be obtained first. Tables C3-C6 have Uc as a function of median sediment size, D50, water depth, Yo, and relative roughness of the bed, RR for quartz sand. Knowing the design and critical velocities the scour regime can be determined (i.e. is the design velocity in the clearwater scour or the live bed scour regime). Clearwater Scour (0.4 U < 1.0):
-Uc
dse( ) ----------------------------------------------1
To simplify the algebra define
k =-tanh -0.31+0.051exp bglo 75 + .
bD5O50
The coefficients co and c1 can then be computed as follows:
co = 2k --------------------------------------------------------------------------------(3)




5
c1 = ---.--...........................................................................((4
Note: It is recommended that if b > 104, that 50 be set equal tol0 in the above equations.
D50 '
If the design velocity is in the live bed regime then the velocity where the maximum scour depth in the live bed range occurs (Ulp) must be determined. For quartz sand this value can be obtained from Table C7. This requires knowledge of the median sediment size and the water depth. The equilibrium (live bed) local scour depth can then be computed using the following equations.
Live Bed Scour 1.0 < U -Uc
de -= c2 UIUj+c3 ----------------------------------(5)
where
k-2.4tanh a(
c2 = ,IPand-------------------------------------------- (6)
(Uc
C3= 2.4 tanhYO---------------------------------------- (7)
U UIp
if >U--,then
fC UC
dSe 2.4 tanh(YO ------------------------------------ (8)
The scour depth for a noncircular single pile can be estimated by multiplying Equations 1 and 5 by a shape coefficient, K1, that corresponds to the particular cross-sectional shape of the pile. Values for K are reproduced in Table C2 from HEC-18.




Definition of symbols

dse equilibrium local scour depth, b circular pile diameter, D50 median diameter of sediment, yo water depth upstream of the pile, U depth averaged velocity upstream of the pile, Ue = critical depth averaged velocity upstream of the pile
= velocity of impending motion of the sediment,
Ulp velocity at the maximum (or peak) scour depth in the live bed scour range




Table ClI. Bed relative roughness, RR, guide.

Bed Condition RR
Laboratory flume, smooth bed- ripple forming sand (D50 < 0.6 mm) 5.0
Laboratory flume, smooth bed non-ripple forming sand (D50 > 0.6 mm) 2.5
Laboratory flume, smooth bed live bed test with dunes 10
Field smooth bed 10
Field moderate bed roughness 15
Field rough bed 20
Table C2. Single pile shape coefficients (information from HEC-18).
Shape
Pile Shape Factor
____ ___ ___ ____ ___ ___ ____ ___ ___K,
Circular 1.0
Square
Flow normal to side I 1.1
Flow normal to edge 0.9




Table C3. Critical velocity Uc, (mis) as a function of median grain diameter D50 (mm), and water
depth yo (in) ) based on quartz sand, fully developed flow and Shield's parameter. Bed
relative roughness, RR = 2.5.
D50
(MM)
____ 0.1 0.2 0.3 0.4 0.5 10.75 1 2 4 6 10
0.5 0.30 0.32 0.33 0.34 0.36 0.41 0.46 0.65 0.94 1.11 1.33
1 0.33 0.34 0.36 0.37 0.39 0.45 0.50 0.72 1.04 1.24 1.50
1.5 0.34 0.36 0.37 0.39 0.41 0.47 0.53 0.76 1.10 1.32 1.60
2 0.351 0.37 0.38 0.40 0.42 0.48 0.541 0.78 1.14 1.371 1.67
yO (in) 2.5 0.35 0.37 0.39 0.40 0.43 0.50 0.56 0.81 1.18 1.41 1.73
3 0.36 0.38 0.40 0.41 0.441 0.51 0.57 0.82 1.20 1.45 1.77
3.5 0.36 0.38 0.40 0.42 0.44 0.51 0.58 0.84 1.23 1.48 1.81
4 0.37 0.39 0.41 0.42 0.45 0.52 0.59 0.85 1.25 1.50 1.84
4.5 0.371 0.39 0.41 0.43 0.45 0.531 0.59 0.86 1.26 1.52 1.87
1___ 5 10.371 0.40 0.41 0.43 0.46 0.531 0.601 0.87 1.281 1.541 1.901
Table C4. Critical velocity Uc (m/s) as a function of median grain diameter D50 (mm), and water
depth yo (in) ) based on quartz sand, fully developed flow and Shield's parameter. Bed
relative roughness, RR = 5.0.
RR=5 D50
(MM)
0.1 0.2 0.3 0.4 0.5 10.75 1 2 4 6 10
0.5 0.30 0.30 0.30 0.31 0.32 0.37 0.42 0.59 0.83 0.98 1.16
1 0.32 0.32 0.33 0.34 0.35 0.41 0.46 0.65 0.94 1.11 1.33
1.5 0.33 0.34 0.34 0.35 0.37 0.43 0.48 0.69 1.00 1.191 1.43
2 0.34 0.35 0.351 0.36 0.38 0.44 0.50 0.72 1.04 1.24 1.50
yO (in) 2.5 0.35 0.35 0.36 0.37 0.391 0.45 0.51 0.74 1.07 1.28 1.56
3 0.35 0.36 0.37 0.38 0.40 0.46 0.52 0.76 1.10 1.32 1.60
3.5 0.36 0.36 0.37 0.38 0.41 0.47 0.53 0.77 1.12 1.35 1.641
4 0.361 0.37 0.38 0.39 0.41 0.48 0.54 0.78 1.14 1.37 16 4.5 0.361 0.37 0.38 0.39 0.42 0.48 0.55 0.80 1.16 1.39 17
5 0.37T 0.38, 0.381 0.401 0.421 0.49 0.55 0.81 1.18 1.41 17

C-6




Table C5. Critical velocity U, (mis) as a function of median grain diameter D50 (mm), and water
depth yo (in) based on quartz sand, fully developed flow and Shield's parameter. Bed
relative roughness, RR = 10.0.
D50
(nu)
S 0.1 0.2 0.3 0.4 0.5 0.75 1 2 4 6 10
1 0.30 0.29 0.29 0.30 0.32 0.37 0.42 0.59 0.83 0.98 1.16
2 0.32 0.32 0.32 0.33 0.35 0.41 0.46 0.65 0.94 1.11 1.33
3 0.33 0.33 0.33 0.34 0.36 0.43 0.48 0.69 1.00 1.19 1.43
4 0.34 0.34 0.341 0.35 0.38 0.44 0.501 0.72 1.04 1.241 1.50
yO (in) 5 0.35 0.35 0.35 0.36 0.39 0.45 0.51 0.74 1.07 1.28 1.56
6 10.36 0.35 0.36 0.37 0.39 0.46 0.52 0.76 1.10 1.32 1.60
8 0.36 0.36 0.37 0.38 0.41 0.48 0.54 0.78 1.14 1.37 1.67
10 0.37 0.37 0.38 0.39 0.41 0.49 0.55 0.81 1.18 1.41 1.73
15 0.381 0.381 0.391 0.40 0.431 0.51 0.581 0.84 1.241 1.491 1.83
____20 0.391 0.391 0.401 0.42 0.441 0.521 0.591 0.871 1.281 1.541 1.90

Table C6. Critical velocity Uc, (mis) as a function of median grain diameter D50 (mm), and water
depth yo (in) based on quartz sand, fully developed flow and Shield's parameter. Bed
relative roughness, RR = 20.
D50
(mm)_S 0.1 0.2 0.3 0.4 0.5 10.75 1 2 4 6 10
1 0.27 0.26 0.27 0.27 0.29 0.34 0.38 0.53 0.73 0.85 0.99
2 0.30 0.29 0.29 0.30 0.32 0.37 0.42 0.59 0.83 0.98 1.16
3 0.31 0.30 0.30 0.32 0.34 0.39 0.44 0.63 0.89 1.06 1.26
4 0.32 0.31 0.311 0.33 0.35 0.41 0.461 0.65 0.94 1.11 1.33
yO (in) 5 0.32 0.32 0.32 0.33 0.361 0.42 0.47 0.68 0.97 1.15 1.39
6 0.33 0.32 0.33 0.34 0.36 0.43 0.48 0.69 1.00 1.19 1.43
8 0.34 0.33 0.34 0.35 0.38 0.44 0.50 0.72 1.04 1.24 1.50
10 0.34 0.34 0.35 0.36 0.39 0.45 0.51 0.74 1.07 1.28 1.56
15 0.,36 0.351 0.36 0.38 0.40 0.47 0.'541 0.'78 1.13 1.36 1.66
____20 0.37 0.361 0.371 0.39.1 0 .40 9' 0S 0.1 1.18 1.41 1.73




Table C7. Velocity at live bed peak, U1 p (in mis), as a function of median grain diameter
D50 (mm), and water depth yo (in) for quartz sand. Taken from Snamenskaya
(1969)
D50
(nu)
0.1 0.2 0.3 0.4 0.5 10.75 1 2 4 6 10
0.5 1.65 1.80 1.92 2.03 2.10 2.32 2.45 2.70 2.90 3.04 3.24
1 2.30 2.44 2.59 2.89 2.82 3.04 3.19 3.47 3.81 3.99 4.18
1.5 2.80 2.95 3.07 3.22 3.33 3.59 3.73 4.03 4.32 4.67 4.93
2 13.221 3.38 3.48 3.64 3.76 4.05 4.18 4.52 4.91 5.201 5.53
2.5 3.58 3.75 3.85 4.00 4.151 4.45 4.611 4.93 5.30 5.64 6.03
3 3.91 4.09 4.19 4.31 4.49 4.80 4.98 5.28 5.70 6.01 6.46
3.5 4.21 4.39 4.51 4.62 4.79 5.10 5.31 5.59 6.06 6.34 6.83
yO (in) 4 4.48 4.67 4.81 4.91 5.07 5.39 5.61 5.91 6.39 6.65 7.17
4.51 4.74 4.93 5.08 5.17 5.32 5.67 5.89 6.22 6.691 6.98 7.48
5 4.99 5.18 5.34 5.43 5.56 5.941 6.15 6.51 6.97 7.28 7.76
6 5.45 5.66 5.82 5.92 6.04 6.43 6.62 7.04 7.47 7.83 8.26
8 6.25 6.51 6.65 6.78 6.87 7.28 7.50 7.94 8.36 8.75 9.24
10 6.95 7.26 7.37 7.54 7.64 7.99 8.26 8.70 9.211 9.51 10.10
151 8.41 8.82 8.951 9.11 9.251 9.54 9.821 10.31 10.93 11.281 11.81
____ 0 9.63 10.13 10.291 10.401 10.591 10.851 11.091 11.69 12.30 12.741 13.221

C-8




APPENDIX D
DETERMINATION OF EFFECTIVE DIAMETER
OF A
COMPLEX STRUCTURE




Determination of Effective Diameter
of a Complex Structure
Introduction:
The majority of local scour data reported in the literature is for single circular piles. The circular pile is also the most common structure for analytic and computational investigations of local sediment scour. Most empirical scour prediction equations are for circular piles with correction coefficients for other shapes. Researchers are also using circular pile equations to estimate local scour depths at complex piers that include pile groups, pile caps and super structure [see e.g. Sheppard and Jones (1998)]. When physical model, local scour tests are performed most of the parameters can be scaled with the exception of the sediment. Only in the case of very large sediment diameters in the prototype can the sediment in the model be scaled properly. In order to account for the improper sediment scaling the relationship between local scour depth and the sediment properties must be known. Sheppard and others have found that the data correlates well
with the dimensionless parameter --(or its reciprocal), where b is the diameter of the pile and D50 is the median diameter of the sediment. In seeking a length scale by which to normalize the sediment size it must be a length that is associated with the local scour (i.e. the sediment size is small or large as compared to what length). The equilibrium scour depth is known to be highly dependent on both the pile diameter and the water depth, at least for a range of these variables (both diameter and water depth have been used to normnalize the scour depth in scour prediction equations). Sheppard's equation has now been validated for a wide range of parameters in the clearwater scour range of velocities. Tests planned for the spring and summer of 2000 will provide additional data for testing this equation in the live bed scour range. In the meantime there is live bed data from Ettema (1980) and Chiew (1984) that support the validity of this equation.
Many local scour model tests are performed at velocities just below transition to live bed conditions. Sheppard's clearvater scour equation can be used to compute the "Effective Diameter", D*, of the structure once the equilibrium scour depth is known.
Sheppard's Local Equilibrium Clearwater Scour Equation for a Circular Pile:
Clearwater Scour (0.4 <1.0):
Uc
dse = (u'\l 1()
b~=c [ C I .01. ---------------------------------- (1)-




To simplify the algebra define

k tanh( -0.31+.051exp( log10lO b + 0 (2)
50

The coefficients co and c1 can then be written as follows:
co anand

C 1 = .------------------------------------------------------------------------------ I4
2
where
dse equilibrium local scour depth, b circular pile diameter, D50 = median diameter of sediment, Yo = water depth upstream of the pile, U = depth averaged velocity upstream of the pile, Uc -critical depth averaged velocity upstream of the pile
= velocity of impending motion of the sediment
Effective Diameter of Complex Pier:
If the equilibrium scour depth for a given set of sediment and flow conditions is known then the effective diameter, D*, can be computed using the above equations. The measured scour depth must first be adjusted for test duration (if scour depth has not reached equilibrium) and velocity (if test was performed below transition velocity).
The problem becomes one of solving a transcendental equation for D* (which can be easily done using an electronic spreadsheet or many hand calculators). Obtain the value of Dm that satisfies the following equation:

UC=1)= c0[c1 1.0] dsUtc Dm -

D-2




where

co 2 k --- - - - - - - - - - - - - - - - - - --(6 )
k =-tanh YO -[0.31+o.051 exp loglo j 0.75 ...... (7)
DM D50 1lo0 m
_D50
1 2' -------------------------------------------------------------- (8)
and yo and D50, are the values from the model test. For some complex piers a real root to this equation does not exist. This simply means that there is no circular pile that will produce the scour depth as that measured for the complex pier (for the given flow and sediment conditions). When this happens a pier with a different shape (one that creates a greater scour depth) must be used as a reference. Using the nomenclature in HEC- 18 for the pier shape factor, K1, Equation 5 becomes
dse (at C= 1) =K, Dm co [c, 1.0].--------------------------------(9)
The problem is then to determine the minimum value of K, that will produce a real root to Equation 9. This can be accomplished by increasing Dm from 0 and determining the maximum value of the right side of Equation 5, then divide the measured scour depth by this maximum value. For example, if the maximum value of is 0.453 m and the measured scour depth for the model pier is 0.5 m the minimum value of the shape factor,
0.500
K1, is 043= 1. 1. In this case the reference pile is one that has a shape factor of 1. 1, which is that of a square pile.
The effective diameter of the prototype pier is obtained by multiplying the model effective diameter by the geometric scale of the model.
D *=Dm*Sg-------------------------------------------------------- (9)
where
D Effective diameter of prototype pile (i.e. diameter of pile with a shape factor, K1,
that will experience the same local scour depth as the prototype pier and,
Sg Geometric Scale of the Model.

D-3




The scour depth of the prototype pier is thus:
dse = K1 Dp co [cl -1.0], -------------------------------------------------------------(10)
where
2 (1
c 2 ---------------------------------------------------------------------------------(11)
co = -k
--1
__Dpl-t 0.75 ad(2
k -tanh -pz -0.31+0.051exp loglo D5oP l 0.75 and ------------(12)
D *D50 D
loglo
5
= ----------- -------------------------------------------------------------------------(13)
Cl D-4-2
D-4