Calculation of Local Scour Depth Around Bridge Pier in Stratified Riverbed
In this study, based on the analysis of the local scour process of bridge pier in stratified riverbed, the concept of critical breakdown velocity is proposed for each soil layer of stratified riverbed, and its computational formal is presented too. And combining with the theory of armor layer, the calculation method of local scour depth around bridge pier in stratified riverbed is proposed. Two soils with different sediment gradations were used to simulate the multiple-layer soil riverbed, the method proposed in this paper is used to calculate the local scour depth of bridge pier, and compared with Liu Baoshan’s method. The effect of the relative size of topsoil and subsoil on local scour is analyzed qualitatively. If the riverbed is upper-fine and lower-coarse, the influence of topsoil on the lower soil scouring is on the wane with increasing the local scour depth after the topsoil is punctured, until it can be largely ignored. However, the similar phenomenon did not occur under the same flow conditions and topsoil thickness for the stratified riverbed with upper-coarse and lower-fine. It indicates that when the topsoil particle size is larger than that of the subsoil, the effect of topsoil on the erosion of subsoil is much greater than when the topsoil particle size is smaller than that of the subsoil.
Keywords - Stratified Riverbed, Local Scour Depth Around Bridge Pier, Critical Breakdown Velocity, Computation Method.