Discrete Analysis of Local Scour Morphology of Bridge Piers Affected by Sediment Storage Dam

Abstract

In order to solve the prediction and protection problems of local pier scour with a downstream sediment storage dam on non-uniform sand riverbeds in mountainous areas, the Xi’an Chanhe Bridge in China was taken as the research object. Through comprehensive physical model experiments, the influence of sediment storage dam layout on the surrounding water flow and local scour morphology around bridge piers was studied. The relationship between boundary conditions and local scour pit morphology was studied using a discrete analysis model. The research results showed that the inflow rate Q was the most significant factor affecting local scour, and local scour generally developed rapidly within 0.5–1.0 h and then gradually reached a dynamic equilibrium. The maximum depth was located within 0.25B in front of the pier relative to the pier width B, and the impact range of local scour behind the pier was [5B,10B]. The recommended layout of a sediment storage dam has a distance between pier and dam L of [8B,11B] and a dam crest elevation Z higher than that of the original riverbed elevation at the bridge pier, which is [0.4B,0.5B]. An improved calculation formula for the local scour depth of bridge piers hs is proposed and verified through experimental measurements to provide a reference for the design and protection of bridge piers with a downstream sediment storage dam.

Keywords

• local scour
• sediment storage dam
• physical model
• discrete analysis
• scour formula