Unascertained Measure Model of Water and Mud Inrush Risk Evaluation in Karst Tunnels and Its Engineering Application

Water and mud inrush is one of the typical geological disasters during tunnel construction in karst areas. In order to effectively control the water and mud inrush risk and guarantee the safety of tunnel construction, an unascertained measure model of water and mud inrush risk evaluation is established based on unascertained measure theory. First, according to geological factors and engineering factors in tunnel zone, unfavorable geology, formation lithology, ground water level, topography and geomorphology, attitude of rocks, contact zones between soluble rock and non-soluble rock, crack in rock stratum, surrounding rock grade, construction technology level, and management level are selected as risk evaluation indexes of water and mud inrush, which constitutes the index system of water and mud inrush risk evaluation. Through collecting and collating information of typical water and mud inrush examples of karst tunnels, the uncertainty measure function of each evaluation index is obtained based on the measured data. Meanwhile, the index weight of each factor is ascertained by entropy-information theory, and the risk grade of water and mud inrush is judged by credible degree recognition criteria. In engineering application, the water and mud inrush risk of Qiyueshan tunnel is evaluated based on the established unascertained measure model. The results show that: (1) The evaluation results agree well with practical construction situation. (2) The unascertained measure model is scientific and reasonable, which can achieve the risk level evaluation of water and mud inrush systematically. (3) The unascertained measure model provides an effective method for water and mud inrush risk evaluation of karst tunnels, which can be applied to practical engineering.