Influences of fault slip induced by dynamic loading on the mechanical responses of tunnels

Abstract

Understanding the mechanical responses of tunnels to fault slip induced by dynamic disturbances is crucial for assessing structural safety and stability. Previously, scholars have focused mainly on the shear properties of rough interfaces, neglecting the influence of stress concentration caused by fault slips on underground engineering projects. Therefore, in this work, laboratory experiments and numerical simulations are conducted to investigate the evolution of stress, displacement, strain energy density (SED), and strain energy release rate (SERR) in the surrounding rock. The results indicate that the stress state in the rock surrounding the fault is complex, and that the failure range of samples with faults is more extensive than that of the samples without faults. The stress concentration at the tunnel crown far exceeds that at other locations under dynamic loading. At an impact load of 52.1 MPa, the peak SED and SERR at the tunnel crown are 1.516 MJ·m⁻³ and 6197.82 MJ·m⁻³·s⁻¹ respectively, these values are 20.76 and 43.84 times greater than those at the floor, respectively. The fault slipping results in significantly higher stress and strain energy levels on the left side of the tunnel (near the fault) than on the right side, leading to a significant increase in the severity of tunnel damage with increasing impact load. Finally, the mechanical responses of the tunnels under the coupled effect of impact loads and fault roughness are investigated. The SERR increases with increasing impact load and fault roughness, and the degree of damage to a tunnel is positively correlated is positively correlated with the SERR. As the joint roughness coefficient (JRC) of the faults increases from 0 (smooth state) to 12.26, the maximum stress σ_max at the crown increases from 120.78 MPa to 241.27 MPa at an impact load of 52.1 MPa. Moreover, the SERR at the crown peaks at 5997.54 MJ·m⁻³·s⁻¹ when JRC = 12.26. As the JRC increases to 17.98, the most severe damage zone moves from the crown to the left side of the floor.