Study on Mechanism of Water and Mud Inrush in Deep-Buried Large-Section Tunnel Crossing Water-Rich Fault Fracture Zone

To study the disaster mechanism and process of water and mud inrush in deep-buried large-section tunnel crossing the water-rich fault fracture zone, based on the project of Dechang tunnel crossing the D2K504 + 245-D2K504 + 360 fault fracture zone, similar model test and numerical simulation were adopted. The parameters of water inflow, seepage pressure evolution, surrounding rock deformation and plastic zone distribution were obtained. The results showed that the water and mud inrush is caused by the joint action of ground stress and seepage water pressure when a deep-buried large-section tunnel passes through the water-rich fault fracture zone, and it has mutability and repetition. Tunnel arch and arch bottom are the weak parts of failure, and the shear instability is easy to occur at the palm surface. In addition, through the simulation study of the advance curtain grouting reinforcement measures, it is considered that the grouting length of 30 m, the radial grouting range of 6 m and the increasing strength of surrounding rock of 40% are the appropriate parameters for the prevention and treatment of Dechang tunnel through the Gaojiawan fault fracture zone. The rationality of the parameters is verified by engineering practice, which provides a basis for the treatment of water and mud inrush.