Research On Local Scour Around Bridge Piers

Riverbed scouring around structural buildings exists expensively in nature and artificial engineerings like bridge pier, spur dike, leading jetty, submarine pipeline, breakwater and so on. Local scour does harm to the structures and is one of main reasons for the damage of structures in hydraulic engineering and coastal engineering. In recent years, along with the rise and increasing development of constructions in hydraulic engineering, more and more attentions have been paid to the issue of local scour and the stability of structures.Based on the coupled equations used to describe the motion of flow and sediment transport, combing with the research on erosion mechanism of bridge pier, the paper derives and establishes hydrodynamic and sediment transport mathematic model to calculate the hydrodynamics and scour around bridge pier, and the Reynolds equations are closed by the standard 2nd-order k-e turbulent model by bringing in the Bousinessq assumption.In order to study the water-flow retardation of bridge piers and abutments when Nanjing Yangtze bridge on Beijing-Shanghai high speed railway is finished, experiment and numerical simulation have been carried on separately to obtain the changes in hydrodynamic condition and riverbed scouring around piers, furthermore, the backwater and the river regime of this region are discussed. In particular, within the numerical simulation, a 2-D flow and sediment mathematical model in curvilinear collocated grid has been developed and non-equilibrium sediment transport is applied in the model. The discrete scheme partial differential equation is induced by the finite volume method. To improve computing speed and the stability, a mended-SIMPLER has been employed here. This routine considers that the pressure correction equation is only used to correct the velocity, and water level is obtained by solving the water level equation, besides, the ambient grid's influence has been taken into account when correcting the velocity. Using this model makes it possible to simulate the fine flow structure and sediment movement around bridge and the distortion of current structure near bridge can be largely avoided.