Risk assessment of water and mud inrush in a tunnel in Chongqing based on analytic hierarchy process

Water and mud inrush is one of the typical geological hazards during tunnel construction in karst area. In weight of water or mud inrush risks of karst tunnels are studied and the index system for water and mud inrush risk evaluation is established based on analytic hierarchy process. The analysis shows that geological structure, formation lithology and groundwater level are the main control ingredients of water or mud inrush risk；geographic and geomorphic conditions, attitude of rock formation are the minor significant factors；surrounding rock mass classification , rainfall are the least important elements. Aiming at a tunnel in Chongqing, combining with the actual geological situation of the tunnel site, the evaluation model is used to evaluate the risk of water and mud inrush in each section, which provides a certain theoretical basis for the prevention and control of water and mud inrush disaster during the tunnel construction.