Pier and Contraction Scour in Cohesive Soils (2004) / Chapter Skim
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Pages 76-84
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From page 76... ...
The value of Vc can be obtained from the EFA tests for cohesive soils or from the equations presented in HEC-18 for cohesionless soils. The water depth for the pier scour calculations is the water depth in the contracted section after the contraction scour has occurred.
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From page 77... ...
Step II -- contraction scour calculation and distribution. Soil: Critical shear stress and erosion function.
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From page 78... ...
Plan view of complex pier scour and contraction scour.
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From page 79... ...
, the maximum scour depth due to contraction scour and pier scour is calculated from Equation 9.10. With these two quantities defining the tangent to the origin and the asymptotic value of the scour depth versus time curve, a hyperbola is defined to describe the entire curve: where Z(t)
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From page 80... ...
The scour depth due to Floods 1 and 2 in the hydrograph will be handled by following the procedure of Figure 9.5d. At this point the situation is reduced to a single Flood 2 that lasts te.
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From page 81... ...
The channel and bridge geometry are used for contraction scour evaluation, including the determination of the contraction ratio. The pier's size, shape, spacing, and angle of attack are used for pier scour calculations.
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From page 82... ...
0 0 .5 1 1 .5 2 2 .5 3 1 9 6 0 1 9 6 3 1 9 6 6 1 9 6 8 1 9 7 1 1 9 7 4 1 9 7 7 1 9 8 0 1 9 8 3 1 9 8 5 1 9 8 8 1 9 9 1 1 9 9 4 1 9 9 7 Y e a r V el oc ity (m /se c) Bridge Geometric Factors Channel Geometric Factors Bridge contraction ratio Channel contraction ratio Bridge opening Bridge contraction length Channel contraction length Type, shape Attack angle Channel water depth Size, length, width (diameter)
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From page 83... ...
83 Figure 9.9. Flow chart of the SRICOS-EFA Program.
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From page 84... ...
The output file includes the following columns: time, flow velocity, water depth, shear stress, maximum scour depth (pier, contraction, or total) , and instantaneous scour depth (pier, contraction, or total)
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