Revised Clear-Water and Live-Bed Contraction Scour Analysis (2021) / Chapter Skim
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From page 71... ...
5-1 Live-Bed Laboratory Testing Results By definition, live-bed conditions require that sediment is supplied to the contracted section from the upstream approach reach. In the CSU flume, live-bed conditions in the 8-ft-wide approach reach were achieved by setting the pump flow at discharges high enough to mobilize the 0.26-mm sand.
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From page 72... ...
5-2 Revised Clear-Water and Live-Bed Contraction Scour Analysis Figure 5-1. Sediment rating curves for the CSU 8-ft flume.
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From page 73... ...
Live-Bed Laboratory Testing Results 5-3 Prior to each live-bed test, the bed was smoothed perfectly flat at a reference elevation of 0.00 ft. At the beginning of each test, water was gradually introduced into the flume.
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5-4 Revised Clear-Water and Live-Bed Contraction Scour Analysis LB_0.50-2.0 Water Surface Evolution-Centerline 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0 10 20 30 40 50 60 70 80 90 El ev ati on (ft ) Station (ft)
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Live-Bed Laboratory Testing Results 5-5 -1.50 -1.25 -1.00 -0.75 -0.50 -0.25 0.00 0.25 0 10 20 30 40 50 60 70 80 El ev ati on , ft Station, ft LB_0.50-2.0 Lidar Bed Profiles Initial bed: Centerline Initial bed: Wall Final bed at 7 hours: Centerline Final bed at 7 hours: Wall Figure 5-4. Initial and final bed profiles from LiDAR scans, Test LB_0.50-2.0.
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From page 76... ...
5-6 Revised Clear-Water and Live-Bed Contraction Scour Analysis Test LB_0.50-2.0 Centerline -1.0 -0.5 0.0 0.5 1.0 0 10 20 30 40 50 60 70 80 90 100 El ev ati on ( ft ) Station (ft)
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From page 77... ...
Live-Bed Laboratory Testing Results 5-7 Shear-stress profiles were developed from the calibrated HEC-RAS model for each of the four live-bed tests at the completion of each 7-hour run. The results are shown in Figure 5-8 for the centerline measurements.
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From page 78... ...
5-8 Revised Clear-Water and Live-Bed Contraction Scour Analysis 5.3 Mild Contraction Ratio Five live-bed contraction scour tests were conducted in the 8-ft-wide indoor flume at CSU with a contracted section 6 ft wide by 85 ft long, giving a contraction ratio B2/B1 = 6/8 = 0.75. Wing walls at 45° transition the flow from the 8-ft-wide approach section into the contracted reach, the same entrance angle used for all clear-water tests.
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From page 79... ...
Live-Bed Laboratory Testing Results 5-9 5.3.1 Bed and Water Surface Profiles Measurement of water surface and bed elevations at the same predetermined flume stations as were used for the clear-water tests (see Table 4-2) were taken periodically during the 7-hour duration of each live-bed test.
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5-10 Revised Clear-Water and Live-Bed Contraction Scour Analysis Figure 5-10. Water surface and bed evolution, Test LB_0.75-2.5.
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Live-Bed Laboratory Testing Results 5-11 Figure 5-11. Initial and final bed profiles from LiDAR scan, Test LB_0.75-2.5.
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5-12 Revised Clear-Water and Live-Bed Contraction Scour Analysis Figure 5-13 (a)
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Live-Bed Laboratory Testing Results 5-13 Figure 5-13 (d)
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From page 84... ...
5-14 Revised Clear-Water and Live-Bed Contraction Scour Analysis Figure 5-15. Initial and final shear-stress profiles for five live-bed tests at the Mild contraction ratio B2 /B1 = 0.75.
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