Research Of Karst Tunnel Water Bursting Hazard Risk Assessment System In The Southwest Mountainous Area

Taken urgent need of water bursting disaster controlling and safety inconstruction of karst tunnels into consideration, large quantity of engineering practiceand theoretical research has been carried out in the disaster forecast and early-warningmechanism domain during the course of karst tunnel construction. With caseinvestigation of water bursting disaster happened in the karst tunnels in the Southwestof China, basic geological factors and conditions affecting and acting on karst waterhazard formation course are analyzed, and risk assessment system is studied andestablished under the condition of special geological environment and complicatedkarst water hydrogeology. The research findings have made some progresses in thetheory and methods of karst water bursting disaster early-warning and forecast, whichare described as follows:（1）For the purpose of finding out the karst development law, groundwaterdistribution and migration characteristics, the modes of karst water migration andreservoir structure are analyzed and summarized under the control of geologicalstructure conditions, and refined geological model of groundwater distribution andmigration is built up.（2）Based on systematic（but not complete） geological data acquisition of145karst water bursting disasters from tunnels built in the study area, styles, probability,water inflow and feature of diachronic distribution of the disaster are discussed, andwith the disaster forming conditions analysis, the controlling and affecting factors arepointed out, and the interaction between the tunnel engineering and karst waterenvironment is researched.（3）Drawing the theory and method of geological hazard risk assessment intostudy, the basic theories of water bursting disaster modeling method and acceptablelevel of risk are deeply studied, and multi-factor comprehensive evaluation method isused to establish the karst water bursting disaster risk assessment system, and grading evaluation criteria is proposed.（4）In view of relationship between the upper-under ground hydrodynamicdevelopment and the tunnel,5evaluating indicator are provide to establish the riskassessment index system, which are solubility of lime rock, geological structureconditions, the water catchment capability of ground surface, karst water circulationrate under the ground, and depth of tunnel relative to the water level. The paper has anin-depth exploration in the methods of index taking-value based on combinationbetween qualitative analysis and quantitative evaluation.（5）Using statistical and geological analysis method, the correlativity ofassessment index and probability and hazard rating of water bursting disaster arequantitatively analyzed, and the weight of all index is determined by way of experts’experience, analytic hierarchy process（AHP）and multivariate linear regression.（6）On the basis of analysis and research above, water bursting disaster riskassessment system in the karst tunnel is established, and the reliability of it is testifiedat the same time, which guarantee reliability and applicability to the systemutilization.（7）Combined with overall process disaster control management which is origincontrol, process control and terminal control, and taking the safety of construction,optimization of support design and environmental protection as premises, the waterbursting disaster countermeasures are put forward corresponding with the riskassessment grade.（8）With the help of assessment system, risk of water bursting disaster in theWumengshan rail tunnel is evaluated, and the evaluation can provide the tunnelconstruction and disaster prevention and control with significant evidence.