Spalling Failure Mechanism of Surrounding Rock in Deep Hard-Rock Tunnels

Under high ground stress and excavation disturbance, brittle spalling failure is a common and serious problem in deep underground engineering. Rock mass failure is often accompanied by compressive shear failure and localized tensile failure, and the heterogeneity of rock mass will affect its failure mode. Therefore, in this paper, Python programming is used to conduct secondary development of the Property module in the Abaqus platform, and the elastic modulus of granite is treated by the Weibull function to achieve fine modeling of rock mass heterogeneity. At the same time, to simulate the influence of homogeneous and heterogeneous rock mass on the failure mode of tunnel surrounding rock, the double shear unified yield strength criterion, maximum tensile stress criterion, and spalling failure strength criterion are introduced. The results show that: (1) the model can effectively simulate the variations of failure range and failure mode of tunnel surrounding rock under uniform and non-uniform distribution; (2) the failure areas of both the heterogeneous and the homogeneous models are concentrated at the arch top and bottom, and the yield stress and shear stress increase with the increase of heterogeneity; (3) the failure form of the top of the tunnel surrounding rock gradually transitions from tensile shear mixed failure to shear failure, accompanied by spalling failure. With the increase of heterogeneity, the failure range of the surrounding rock expands, and the possibility of spalling failure at the top of the surrounding rock increases. In short, the rock mass heterogeneity will lead to uneven distribution of stress inside the rock mass, affect the failure form of the surrounding rock, and increase the risk of the surrounding rock spalling. Therefore, this study can provide a reference for the excavation of heterogeneous surrounding rock in deep tunnels.