Pier and Contraction Scour in Cohesive Soils (2004) / Chapter Skim
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THE PROBLEM ADDRESSED This project deals with pier scour and contraction scour in cohesive soils. A previous project performed by the same team of researchers began in 1990 and was sponsored by SUMMARY PIER AND CONTRACTION SCOUR IN COHESIVE SOILS
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APPROACH SELECTED TO SOLVE THE PROBLEM The approach selected to solve the problem of predicting the scour depth versus time for complex piers in a contracted channel and for a given velocity hydrograph was based on a combination of a review of existing knowledge, flume tests, numerical simulations, fundamental principles in method development, and verification of the method against available data. The review of existing knowledge avoided duplication of effort and helped to establish a solid foundation.
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The method is based on the calculation of two basic parameters: the maximum depth of pier scour and the initial rate of scour. The maximum depth of scour is based on an equation obtained from flume tests and the initial rate is based on an equation giving the initial shear stress obtained from numerical simulations.
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SRICOS-EFA METHOD FOR INITIAL SCOUR RATE AT COMPLEX PIERS A set of numerical simulations was performed to study the maximum shear stress around a pier, including the effects of shallow water depth, rectangular shapes, angle of attack on rectangular shapes, and spacing between piers positioned in a row perpendicular to the flow. The proposed equation for the maximum shear stress is in the form of the equation for the cylindrical pier in deep water with correction factors based on the results of the numerical simulations.
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Equations are also proposed for the uniform contraction scour depth as well as the location of the scour depths. SRICOS-EFA METHOD FOR INITIAL CONTRACTION SCOUR RATE A set of numerical simulations were performed to study the maximum shear stress around the contraction of a channel, including the effects of the ratio of the contracted channel width over the approach channel width, transition angle, water depth, and contracted channel length.
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The equivalent time is the time required for the ith velocity on the hydrograph to scour the soil to a depth equal to the depth scoured by all of the velocities occurring prior to the ith velocity; 9. Read the additional scour generated by the ith velocity starting at the equivalent time and ending at the equivalent time plus the time increment; and 10.
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From page 7... ...
The SRICOS-EFA Method program be transferred to a Windows™ environment; 3. The project be continued to solve abutment scour, the last major unsolved scour problem in cohesive soils; and 4.
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