Stochastic analysis of fault dislocation induced by tunnel excavation considering distribution characteristics of joints in fracture zones

Tunnel excavation often causes the dislocation of adjacent faults, and further induces rockbursts, earthquakes and other disasters. Due to the complex physical and mechanical characteristics of rock mass, the fault exhibits discontinuity, nonlinear and anisotropy and has the random distribution of joints, which makes the mechanism of adjacent fault dislocation induced by tunnel excavation still unclear. A multi-scale model is established based on the continuous-discrete coupling method. The synthetic rock mass model based on the discrete element method is used to simulate the fault damage zone, and the finite difference method is used to describe the macroscopic dynamic characteristics of the upper and lower walls. The influence laws of the random distribution characteristics of joints on the excavation simulation of a near-fault tunnel are explored. The results show that the randomness of joints in the fracture zone has a significant effect on fault dislocation. The fault dislocation increases with the mean dip angle of joints closer to that of fault. In the case of orthogonal tests, the variance of dip angle has small effects on the mean value of final dislocation. The increase of the mean and variance of joint length causes the fault prone to dislocation. The greater the joint density, the more broken the media in the fracture zone, the lower the overall strength and stiffness, and the weaker the resistance to dislocation. Through a comparative analysis, the influence degree of distribution characteristic parameters of joints on the mean value of fault dislocation is: density > mean value of dip angle > mean value of length > standard deviation of length > standard deviation of dip angle. When the significance level is 0.05, the influences of joint density on the momentum of fault dislocation reach a significant level (p < 0.05).