Numerical Simulation of Fracture Failure Characteristics of Rock-Mass with Multiple Nonparallel Fractures Under Seepage Stress Coupling

Based on the inclusion theory, the calculation formula of additional water pressure caused by the change of external stress state of fracture water in rock-mass is deduced, and its rationality and correctness are verified by numerical experiments. Then, using the rock fracture process analysis system RFPA2D-flow and considering the influence of additional water pressure, the fracture failure process of rock-mass with multiple (2, 3 and 4 fractures) nonparallel fractures (dip angles are not repeatedly selected from 0°, 30°, 45°, 60° and 90°) under the coupling action of stress and seepage is numerically simulated, and the following conclusions are obtained: (1) for rock-mass with two nonparallel fractures, large deformation and failure occur at the fracture position with an inclination of 0° because the fracture strike is perpendicular to the loading direction; In addition, the rock-mass first breaks at the fracture position with low strength, and gradually develops into overall failure, while the other fracture position is relatively complete. (2) For the rock-mass with 3 and 4 nonparallel fractures, similar to the rock-mass with 2 nonparallel fractures, the fracture failure of the rock-mass mainly occurs at the fracture position with low strength, the difference is that the number of fractures is more, and the rock bridge between fractures is connected, and the failure range is larger. (3) For the strength of fractured rock-mass, the fracture strength of rock-mass with multiple nonparallel fractures decreases gradually with the increase of fracture density.