Investigation of the failure characteristics of fissure tunnels under dynamic and static combinations

Abstract

Considering the expansion of mining operations into increasingly deeper areas, it is imperative to assess the influence of dynamic disturbance loads on the security of deep tunnels. Here, via AUTODYN finite difference software, a numerical analysis of the fracture characteristics of a fractured tunnel was employed under the coupled action of in-situ stress and dynamic disturbance loads. The experimental setup comprised a tunnel model with “I-shaped” cracks, and a drop impact device (DID) was employed to generate dynamic wave loads. A crack fracture test (CFT) was utilized to gather information on the fracture process, including initiation time and average propagation rate. A series of combined scenarios were subsequently simulated to replicate various in situ stress levels (ranging from 0.5 to 2.5 MPa) and dynamic loads. The results indicate that with increasing in situ stress, the crack propagation rate, crack propagation length, and crack break time (CBT) decrease; moreover, the circumferential tensile stress concentration factor in the tunnel also decreases, enhancing tunnel stability. Finally, changes in ground stress influence the propagation path of cracks.