Influence of Fault Geometric and Mechanical Parameters on Surrounding Rock Behavior in a Deep Fault-Crossing Roadway

Although fault-controlled instability of underground excavation has been widely studied, systematic analyses of how key fault geometric and mechanical parameters affect surrounding-rock behavior in deep hard-rock mine roadways remain limited. This study takes a deep roadway as the engineering background and uses numerical simulation to investigate the effects of fault thickness, fault dip angle, fault mechanical properties, and contact parameters on the initial deformation state, post-excavation deformation, and plastic-zone evolution of surrounding rock. The results indicate that the surrounding rock is already in a non-uniform initial state controlled by fault disturbance prior to excavation. Increasing fault thickness expands the initial high-deformation zone; fault dip angle mainly changes the spatial distribution pattern of the initial deformation field; and increasing either the fault mechanical parameters or the contact parameters reduces deformation concentration in the vicinity of the fault. After roadway excavation, deformation is mainly concentrated in the fault–roadway intersection zone, and roof deformation along the roadway axis shows distinct local peaks and an asymmetric distribution. The maximum roof deformation continues to increase with the increase of fault thickness (the deformation increases by 218% from 1 m to 5 m), and smaller fault dip angle conditions are prone to local large deformation. In contrast, higher fault mechanical parameters and contact parameters can both effectively suppress roof deformation, with the contact parameters exerting more significant control (as the contact parameter increased from C1 to C5, the maximum roof deformation decreased by approximately 75%). The plastic zone mainly develops at the fault–roadway intersection and is dominated by shear plasticity, accompanied by tensile plasticity. Increasing fault thickness significantly enlarges the plastic-zone volume and strengthens the shear-dominated failure characteristic; fault dip angle mainly controls the propagation direction and morphology of the plastic zone; and increasing the fault mechanical parameters and contact parameters both help reduce the extent of the plastic zone. These findings can provide a theoretical basis for zoned support design and differentiated stability control of roadways crossing faults in deep metal mines.