Stability Implications of Non-Persistent Joints in Large-Section Tunnel Sourrounding Rock

Abstract

In the construction of large-span tunnels, the degree of joint development within the surrounding rock demonstrates heightened sensitivity and exerts a critical influence on the stability of the rock mass. To gain deeper insight into the influence of non-persistent joints on the stability of surrounding rock in large-span tunnels, a reliable discrete element numerical model was established based on the referenced tunnel project. By adopting the area of shear slip zones as a stability criterion, the safety factor of the surrounding rock was evaluated, and the effects of joint trace length, rock bridge ratio, and relative rock bridge dip angle on surrounding rock stability were further analysed. The results indicate that the safety factor first increases and then decreases with increasing joint trace length. Variations in the rock bridge ratio lead to changes in crack propagation modes: when the rock bridge length is smaller than the joint spacing, the stability of the surrounding rock is only slightly affected. The influence of the relative rock bridge dip angle on tunnel stability is comparatively minor. These findings may provide valuable reference for the design and construction of large-span tunnels.