Bridge Risk Assessment Under Tailings Dam Failure Hazard With GIS And Massflow Simulation

With the increasing of the coverage range and mileage of the highway in China and the improvement of construction technology,it is important to evaluate the risks in bridge engineering under disastrous conditions.Tailings dam,which are used for storage of metallic and non-metallic tailings,are built by intercepting ditches or enclosures.This is one of the man-made sources for debris flow with gravitational potential energy,and the failure of the tailings dam will have significant damage on the downstream roadways and bridges.It is necessary and important to optimize the design of roadways,bridges and tunnels,and control the risks,which will be beneficial to the practical work.By integrating the geographic information system(GIS),numerical simulation methods,and risk assessment theory,this thesis evaluates the risks of the downstream bridges caused by a tailings dam besides a highway.The summary of the thesis is in the following.(1)With literature review,the current state-of-art for failure of tailings dam,risk evaluation for bridges,and debris flow are presented.Then,the risk evaluation of bridges under disastrous conditions is summarized in the four respects: a)the mechanism and methods for failure of tailing dam;b)the parameters of the dynamics of debris flow and the calculation methods;c)the risk of the bridges caused by the debris flows and the simulation methods;d)the risk evaluation theory and methods for bridge engineering;(2)GIS technology is used for simulating the failure of tailing dam and risk evaluation in bridge engineering.By integrating the functions of spatial data processing and analysis of ArcGIS,and the simulation of the debris flows under complicated terrain conditions of Massflow,the debris flows caused by dam failure of taking reservoirs are simulated numerically.With the results,ANSYS,the software for finite element analysis,is used for simulating the impact of the bridge pier from the debris flow,such that the key parameters,for example the max stress of the bridge piers and the max displacement of the bridge pier top,can be obtained.By multiplying the velocity and the depth of the debris flow for each point,the degree of the risk in the impacting area can be evaluated,which can be used for the selection of roadway line,the arrangement for bridge holes and hips,the selection of the structures,and the design of the protection.The max overturning moment of the pier from the debris is the parameter for evaluating the pier under the worst working condition,which will be used for analyzing the impact from the debris flow and evaluating the risk loss.The risk assessment system for dam failure and risk loss assessment for the bridge structures,are established.With questionnaire method and expert scoring method,the risk of bridges is evaluated.The risk control method of bridge design in the impacting areas of debris flow and the corresponding suggestions are proposed.