Coupled hydro-mechanical analysis for water inrush of fractured rock masses using the discontinuous deformation analysis

Water inrush is one of the most frequent geohazards during tunnel or mining excavation, and the study of the water-resisting stratum is of great significance in mitigating and preventing this disaster. Aiming at the fractured water-resisting rock mass ahead of the tunnel face, the discontinuous deformation analysis (DDA) coupled hydro-mechanical method was adopted to shed light on the failure process of the water-resisting stratum. The coupled method was implemented, including introducing single fracture flow equations, assembling the global conductivity equation, coupling seepage force, and updating the discrete fracture network. Then, after validating the coupled method by comparing the numerical results with theoretical solutions and experimental measurements, a real inrush case of Yonglian tunnel in a water-rich fault fracture zone was simulated to study the influence of the thickness of the water-resisting structure, stratum stress, and seepage force on the evolution characteristic of the geohazard. The simulation results could well depict the failure mechanism of the water-resisting structure, and the obtained results considering the progressive damage were more correspond to practice than those based on continuous assumption, showing the capacity of the coupled method for studying practical engineering geohazards.