Study on the damage mechanism of water and mud inrush in a tunnel with water-rich fault zones based on experiment and numerical modeling

Abstract

Tunnel construction has become increasingly challenging in water-rich fault fracture zones, and failure evolution of tunnel traversing is essential for understanding the deformation characteristics. In this study, the dynamic evolution of water and mud inrush in tunnels crossing water-rich fault zones was investigated by the experimental test and numerical simulation based on Discrete Element Method (DEM) and Finite Difference Method (FDM). According to the experimental results, two abrupt points in water inflow can be observed in model tests, with inflow volumes of 0.102 m³/h and 0.318 m³/h. The water pressure variation at the tunnel haunch is 2.87 % and 20.15 %, and the tunnel crown is 5.85 % and 17.50 %, respectively. The safety thickness of the burst-prevention layer is about 5 cm in the experiment. The water inrush and water pressure are compared for both the experiment and numerical simulation and a good agreement has been obtained. The numerical results show that the fault near the tunnel face has an explosive potential, while areas farther away experience delays in destruction. The time required to form a new settlement trough within the fault progressively increases, and the curvature of the fault slip surface grows over time. The fault area is influenced in three directions, with the vertical direction being the most affected, measuring 1.2 to 1.5 times the horizontal direction. Damage in the horizontal direction significantly diminishes when the affected area extends to 2.36 times the tunnel diameter. The findings could provide valuable guidance for preventing water and mud inrush risks during tunnel construction.