Abstract

Based on the characteristics of local piers scouring after built the sediment control dam in the downstream of the bridge, by the monomer model experiment of flume sixty groups of local piers scouring have been carried on, the principle and the influence factors of the local piers scouring have been analyzed. The results of series model experiment show that, with the sediment control dams, the local scouring of the piers, on one hand, is influenced by the approach velocity, down-shearing vortex, dimension of the piers, diameter and graded of the bed sand; on the other hand, it is affected by the elevation of the dam and distance between the pier and the dam. Therefore, the concept of “control slope” is introduced in order to reflect the impacts of the sediment control dam to the piers. Based on the theoretical deduction and dimension analysis, the equation, which is used to calculate the local scouring with no-uniform bed sand, is acquired by multivariate regression analysis, has been testified by the flume experiment and has got a good result. The optimum value of control slope and the equation of local piers scouring with that dam provide valuable references for the shallow foundation bridge design.

Keywords: bridge with shallow foundation, local scouring, U-shaped vortex, sediment control dam, control slope