Preliminary study on risk assessment of water and mud inrush in karst tunnel

Through analysis of more than 20 karst tunnels a risk classification system for water and mud inrush is put forth by means of qualitative and quantitative analysis on the condition that fully considering the operability and applicability of the methods used in the analysis. The 1st order evaluation index involves the material components of the soluble rocks and geotectonic conditions as well as field effect conditions; the 2nd order evaluation index involves 13 influencing factors such as the width of the faults and pressure of the confined water and the landform as well as the buried depth of the tunnel. In addition, the weights are determined with ATP and the degree of membership by means of qualitative and quantitative method, and the corresponding protect measures is drafted in light of the risk of water or mud inrush in the tunnel. The results show that the very risky part of water or mud inrush in Maoba syncline is 992 m long that accounting for 54.7% of the total tunnel.