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Title: Local sediment scour flume tests for Hallandale Beach Boulevard
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Permanent Link: http://ufdc.ufl.edu/UF00089493/00001
 Material Information
Title: Local sediment scour flume tests for Hallandale Beach Boulevard
Physical Description: Book
Creator: Sheppard, D. M.
Publisher: Department of Coastal and Oceanographic Engineering, University of Florida
Publication Date: 1995
 Subjects
Subject: Coastal Engineering
Spatial Coverage: North America -- United States of America -- Florida
 Notes
Funding: This publication is being made available as part of the report series written by the faculty, staff, and students of the Coastal and Oceanographic Program of the Department of Civil and Coastal Engineering.
 Record Information
Bibliographic ID: UF00089493
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
    Cover
        Cover
    Title Page
        Title Page
    Local sediment scour flume tests for Hallandale Beach Boulevard (ICWW) bridge piers, Hallandale (Broward County), Florida
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
    Appendix
        Page 9
Full Text



UFL/COEL-95/023


LOCAL SEDIMENT SCOUR FLUME TESTS FOR HALLANDALE
BEACH BOULEVARD (ICWW) BRIDGE PIERS, HALLANDALE
(BROWARD COUNTY), FLORIDA



FINAL REPORT



By



D. M. Sheppard


September 1995


Submitted to:

Reynolds, Smith and Hills, Inc.
and
Florida Department of Transportation
District 4











FINAL REPORT


LOCAL SEDIMENT SCOUR FLUME TESTS FOR
HALLANDALE BEACH BOULEVARD (ICWW) BRIDGE PIERS,
HALLANDALE (BROWARD COUNTY), FLORIDA




SUBMITTED TO:
REYNOLDS, SMITH AND HILLS, INC.
AND
FLORIDA DEPARTMENT OF TRANSPORTATION
DISTRICT 4




BY:
D.M. SHEPPARD
COASTAL AND OCEANOGRAPHIC ENGINEERING DEPARTMENT
UNIVERSITY OF FLORIDA






WPI No. 4110572
State Project No. 86200-1515
UF Account No. 4910 4511 303 12
UPN No. 95030991


SEPTEMBER 1995







LOCAL SEDIMENT SCOUR FLUME TESTS FOR
HALLANDALE BEACH BOULEVARD (ICWW) BRIDGE PIERS,
HALLANDALE (BROWARD COUNTY), FLORIDA


INTRODUCTION:

The bridge over the Intracoastal Waterway on Hallandale Beach Boulevard in Broward
County, Florida is being replaced. Both existing and replacement bridges are Bascule type
bridges. The east and west bound roadways are separated and, thus, there will be two similar
piers in close proximity to each other on each side of the channel. There is also a small skew and
misalignment to the flow. In order to determine the maximum local pier scour that will occur
during a design storm event, model studies were conducted in the Hydraulics Flume at the
University of Florida. The results of this test are reported here along with recommended design
local pier scour depths for 100 and 500 year storm events.


OBJECTIVES:

The primary objective of this work was to determine the maximum equilibrium local scour
depths (scour depths that will occur at transition from clear water to live bed conditions) that will
occur near the replacement bridge at Hallandale Beach Boulevard over the Intracoastal Waterway
during a 1 in 100 year design storm event.


EXPERIMENTAL PLAN AND PROCEDURES FOR THE TRANSITION TESTS:

The test was conducted in the 100 ft long x 8 ft wide x 2.5 ft deep flume in the Hydraulics
Laboratory in the Civil Engineering Department at the University of Florida. This flume has a 100
hp pump and maximum discharge (with the existing weir) of 38.8 ft3/sec (1100 1/sec).

The piers were analyzed to determine which combination would be most scour suseptable.
It was determined that, in this case, the piers in the greatest water depth would experience the
greatest local scour depth. Thus, the test was performed in a water depth of 5.8 in
(corresponding to a 100 year water depth of 23.2 ft (7.1 m)).

The following tasks were performed:

Task 1.
A. Models of the proposed piers for the replacement bridge were designed and constructed
(see Figures 1 3).
B. The models were placed in the flume, the sediment in the test area compacted and
leveled, and the instrumentation calibrated (see Figures 4 and 5).
C. A 26 hour duration local scour test was conducted with flows near the critical depth
average velocity (U/U, = 0.93). U, was computed using Shield's Parameter.







D. The flume was drained and the post experiment measurements were made.


Task 2.
A. The data was reduced and analyzed and corrections made to the results for:
1) the duration of the test (26 hours) not being sufficient to achieve equilibrium, and
2) the depth average velocity during the test (0.80 ft/sec) being slightly less than unity.

Task 3. The final report was written.


RESULTS:

The environmental parameters for the test are given in Table 1. The median sediment
grain diameter (Dso) used in the test was 0.165 mm and the sediment size standard deviation (a)
was 1.29. Table 2 contains the maximum measured and extrapolated scour depths obtained
during the test. The extrapolated scour depths are computed by making corrections to the
measured values for the test duration not being sufficiently long to reach equilibrium and U/Uc for
the test being less than one. Table 3 gives the recommended design local pier scour depths for the
proposed piers. Table 3 also gives estimates of local pier scour depths for a 500 year storm.

Drawings of the model piers are given in Figures 1-3. Photographs of the model piers
prior to start of the test are shown in Figures 4 and 5. Figures 6 8 are photographs of the local
scour after the 26 hour test. The test was designed to provide a conservative estimate of the
maximum local scour that will occur the design storm event. An outline of some of the steps
taken to insure that the scour depths are conservative are given in the appendix.

Table 1. Environmental Parameters.

Bridge: Hallandale Beach Boulevard Bridge over the Intracoastal Waterway in Hallandale,
Broward County, Florida. Both existing and replacement bridges are Bascule type
bridges. Separate piers for east and west bound lanes with slight skew to the
channel.
General: The piers consist of 16 (4 ft diameter) circular piles as shown in Figures 1 and 3.
The bottom of the waterline pile cap is located 12.2 ft above the unscoured bed for
the pier in the deepest water. The piers for the east and west bound lanes are in
close proximity to each other with a slight skew to the flow (9.4) as shown in
Figures 1 and 2. The purpose of these scale model flume tests is to provide design
local scour depths for these structures. The median sediment diameter, D50, and
standard deviation, c, of the sediment used in the flume tests were 0.165 mm and
1.29 respectively.
Scale: Water Water Depth Average Computed Critical Flow Duration
Depth: Temperature: Velocity (U): Depth Average Skew of Test:
Velocity (Uc): Angle:
1 : 48 5.8" 31.80 C 0.80 ft/sec 0.86 ft/sec 9.4 26 hr














Table 2. Measured and Extrapolated Model Scour Results.


Table 3. Predicted Local Scour Depths For Prototype Structures.


Maximum Scour Depth Measured
at the End of the 26 Hour Test: 3.77 in 9.58 cm
Maximum Equilibrium Scour Depths:
(Corrections made for duration (1.02) and
velocity (1.018)) 4.27 in 10.84 cm


Pier: English Metric
No. 2 Near Station 23 + 80
100 year water depth = 22.1 ft (6.74 m) 17.1 ft 5.21 m
No. 2 Near Station 23 + 80
500 year water depth = 28.1 ft (8.57 m) 20.1 ft 6.13 m
No. 3 Near Station 24 + 14
100 year water depth = 3.4 ft (1.04 m) 7.9 ft 2.41 m
No. 3 Near Station 24 + 14
500 year water depth = 9.4 ft (2.87 m) 16.3 ft 4.97 m








14.56'


3 @ 4.10'

0 0 0 0



0 0 0 0


0 0 0 0




0 0 0 0


*-0.47'
-0.19'




0








0.93'

r-0.19'


L_~- K"tl t


Prototype
100-yeor Surge
Water Level
+6.4'
0,84'


0.19'


Prototype
Sond Bed
Elevotion -
15.7' -7


Sond.
Bed


Flume Bottom


Figure 1. Hallandale Bridge Pier Model.


1.63'


3.06'


13.5'


I,


////////







SKEW ANGLE
9.40140

/-


2.676'


FLOW


Figure 2. Plan View of Hallandale Bridge Piers for East and West Bound Lanes.


Figure 3. Isometric View of Hallandale Bridge Piers.



























Figure 4. View of Model Piers from Upstream Prior to Test.


Figure 5. Close-up View of Model Piers Prior to Test.

































Figure 6. Upstream View of Local Scour after 26 Hour Test.


h S


Figure 7. Close-up View of Local Scour After 26 Hour Test.


-2;. .











--.--:3 .



low-~s


Figure 8. Close-up View of Local Scour After 26 Hour Test.






8


;iq

c







APPENDIX


Steps were taken in this test to produce a conservative value of design, local pier scour
depth. These include the following:

1. The test was conducted near transition from clear water to live bed scour conditions (and
the results extrapolated to transition, U/U, = 1). Flow velocities greater or less than
critical will produce smaller equilibrium scour depths.
2. The sediment grain size distribution used in the test area of the flume is very narrow with a
relatively small standard deviation, a (1.29). Researchers have shown that with all other
conditions being the same, local scour depths increase with increasing uniformity of grain
size.
3. The 26 hour duration of these tests is sufficiently long to minimize errors in extrapolating
the results to equilibrium conditions.
4. Predicted one in one hundred year (storm return interval) water elevation for the site was
used to determine the water depth for this test even though peak velocities occur at water
elevations less than the maximum value. In general, equilibrium scour depths increase
with water depth up to a depth equal a structure diameter to water depth ratio of about
three.
5. The scour producing event is assumed to be of sufficient duration that equilibrium scour
depths are achieved. It is the author's opinion that the duration of most storm events in
Florida is not sufficient to create equilibrium scour depths, even on the leading edge of a
pier structure and certainly not in the interior or near the down stream end.
6. For large, complex, multiple pile structures the variation in the equilibrium scour depth
near the structure can be significant. However, until this phenomena is better understood
and predictable, we recommend that the maximum scour depth be used throughout the
structure. This, along with the above items, results in a conservative estimate of design
local pier scour depth.




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