Numerical Simulation And Study On Debris Flow Impacting The Bridge Pier In Loess Area

Loess is widely distributed in our country with a total area of 640000km2;It is a special kind of soil deposit,which has low resistance to erosion and gravity erosion properties.The instability phenomenon of ditch bank collapse,landslide and slide collapse provide the main materials for the formation of debris flow in loess Area;The phenomenon of Erosion gully,suffusion and gully slope loess also provide materials for the debris flow.The event of debris flow destroyed the structure of highway and railway is increasing in recent years,especially the bridge;Take it as background,and based on the research methods and conclusions of debris flow both from home and abroad,at the same time,combined with the experience of fluid mechanics,then the composition and main properties of debris flow in loess area are fully understand.For using the results and ANSYS Workbench,set up a total of 15 kinds of working conditions about debris flow impacting bridge piers,with 2-way FSI simulation models to be analysed.With a comprehensive analysis of the simulation results,some conclusions are obtained and as followed:(1)The dangers of paroxysmal debris flow formed by the collapse of the Dammed Lake are pessimistic.Taking the initial height of debris flow is 16 m as a case,pier concrete in the tensile strength and shear strength can not meet the requirements,the stress is fully borne by the corresponding reinforcement.In addition,the concrete in the compression zone is also on the brink of danger.Therefore,in this case,even if the suitable reinforcement beam,there still have the possibility to be destroyed.(2)Compare the simulation and the calculation results of debris flow impact pressure by the formula,which recommended in the code for design of debris flow disaster prevention and control engineering,found that the recommended formula is safety.(3)The impact pressure from large stones mainly affect the bridge pier's safety in three aspects: Breaking strength,stability and Destroy the concrete nearby the collision point.(4)Due to the obstruction by pier,it strengthen the local sapping,and explain the reasons for the formation of the pit nearby impulse faces.(5)The capping beam can greatly increase strength and stability of the piers.(6)Impact angle can affect piers in two aspects: changing impulse face area and affecting the flow field nearby the post column by the front one.(7)As far as possible to design circular cross-section piers,in order to meet the needs of the strength and stability in Debris flow prone area.In addition,some corresponding improvement advices for each problem are put forward in this paper.