Hydromechanical Coupled Analysis of Water Inrush in a Karst Cave-Fracture Rock System: A Case Study

Abstract

The water diversion tunnel of the Suki-Kinari hydropower station in Pakistan passes through deep valleys with karst caves. Water and mud inrush disasters occurred during tunnel construction because of the adequate water supply from valleys and numerous flow channels. In this work, we develop a karst cave-discrete fracture network model using the C++ code and conduct numerical simulations by ABAQUS version 2018 on a water inrush disaster. Then, considering different strengths and permeability in the reinforced area, we discuss the reinforcement of the fractured rock mass in order to prevent water inrush. Numerical results show that the combination of an increase in strength and one order of magnitude reduction in permeability of fractures is an effective measurement for preventing water inrush. For the specific geological conditions of the A6a diversion tunnel, numerical results indicate that the largest deformation of tunnel offsets toward the orientation of the karst cave. The influence of the relative position of the karst cave varies with cave water pressure, indicating it is essential to consider the relative position of the karst cave and cave water pressure simultaneously for water inrush assessment. In addition, the extent of symmetric deformation is also affected by the relative position between the karst cave and the tunnel.