Study on the risk assessment on karst collapse in linear engineering

In recent years, more and more high-level linear engineering such as high-level road and railway as well as oil pipeline passes through karst area. Karst collapse has become one of the major hidden dangers having to be faced in the linear engineering in karst area. At present, linear engineering project will conduct geological hazard zoning in the early phase. However, most of the works are qualitative and no special evaluation on karst collapse. Therefore, considering the influencing factors of karst collapse and different stage of linear engineering, different assessment methods and indicators are proposed from three levels, i.e. point, line and plane, and three examples are given at the same time, which will provide references for future linear projects that crossing the karst area. Plane and line assessment both use the Geographical Information System (GIS) and Analytic Hierarchy Process (A H P). Plane assessment suits for the feasibility stage that geological data are not clear. Assessment areais1 kilometer on both sides of the line and assessment factors are karst developed level, geological structure, landform type, sinkhole, subterranean river, vertical feature, karst spring and pumping wells distribution. Line assessment suits for preliminary design stage that geological data are clearer. Assessment areais15 meters on both sides of the line and assessment factors are bedrock lithology, line karst rate, soil thickness, soil properties, water level and relation between the water level and bedrock surface. And point assessment is suitable for the key sections, using the method of comprehensive analysis on the dynamic conditions of the karst collapse and the collapse resistance property of the earth. Three indexes, critical gradient, critical velocity and critical water level, which reflect the dynamic conditions of the groundwater, are used as the assessment factors.