Piers Local Scour Disasters Mechanism And Disaster Risk Assessment Research

Bridge is the main traffic buildings across the rivers, bridge instability collapsedcan cause significant casualties, property losses and undesirable social influence.Local scour bridge pier is cause instability damaged by flood disaster happenedthe main reason, in recent years, many scholars at home and abroad for local scourpiers the broad and deep research and made a detailed study of achievement, butbecause the flow field near the bridge pier is very complex, sediment movementvarious in form, the influence factors of the pier scour are numerous, yet people toflow pattern around bridge pier, the problems such as local scour mechanism is stillvery limited. So the study of local scour mechanism and the pier of local scourdisaster risk assessment has important significance.Taking in the previous research results and research method, based on thecomputational fluid dynamics analysis software FLUENT pier local scour disastersformation mechanism and local scour disaster risk assessment, mainly on thefollowing work and get the corresponding results:1.This paper based on the computational fluid dynamics software FLUENTaround bridge pier to complex flow field simulation calculation, analyzing around thepier flow field andriverbed shear stress distribution.2. On the different flow rate conditions of the flow field simulation, analysis, theriver bed maximum shear stress occurred in the pier shoulder on both sides of about70°at the local scour here, the pier behind the occurrence of flow separation. Withthe flow velocity, river bed shear stress dramatically larger, local scour will becomelarger.3. Analysis to set up the pier local scour, set of four different pier diameter, tocompare the flow field, we can see with the pier diameter increases, variable severelocal scour. The piers of the same size, the most dramatic impact of the rectangularpiers on the water flow around the state formation round end pier scour minimum, setdifferent spacing of the piers simulation calculations on the pier spacing is greater than eight times the pier diameter, local scour is not affected, simulate the flow fieldof the elevated pile foundation, the observed elevated pile foundation is on the middleof the first two rows of pile.4. This paper the establishment of local scour hazard evaluation system andvulnerability assessment index system, the use of the Analytic Hierarchy Process(AHP) to calculate the weight of each index.5. Comprehensive index of local scour hazard evaluation models andvulnerability assessment model, using the model in a hierarchy of risk index andvulnerability index criteria, and based on risk rating and level of vulnerability todetermine the level of risk.