3D Numerical Simulation on the Failure Mechanism of Tunnel Working Face by Particle Flow Code

Collapse of tunnel working face often occurred in tunnels constructed in cracked rock. The collapse has two forms, the one is arched collapse which has stable slumping arch before the tunnel working face, the other is caving collapse which the pit occurs in the ground surface before the tunnel working face. The effects of buried depth and surrounding rock strength on the failure mechanism of tunnel working face were studied through series numerical simulations by using PFC3D. The input parameters of PFC3D such as particle size, friction coefficient, bonded strength and so on were calibrated by numerical triaxial test. The calculating results indicate that the collapse of tunnel working face initiates from its upper part and progressively develop upward. And in the case of shallow buried, if the surrounding rock has high strength, the tunnel working face can keep self-stabilization, while the surrounding rock strength is low, collapse of tunnel working face occurs easily and it is likely to spread to the ground surface. Meanwhile, the smaller the buried depth is, the more easily the caving collapse of tunnel working face occurs.