Simulation of cracking near a large underground cavern in a discontinuous rock mass using the expanded distinct element method

The rock masses in a construction site of underground cavern are generally not continuous, due to the presence of discontinuities, such as bedding, joints, faults and fractures. The performance of an underground cavern is principally ruled by the mechanical behaviors of the discontinuities in the vicinity of the cavern. A number of experimental and numerical investigations have demonstrated the significant influences of discontinuities on the mechanical, thermal and hydraulic behaviors of discontinuous rock masses, indicating that the deformation mechanism and stability of rock structures in the discontinuous rock masses depend not only on the existing discontinuities but also on the new cracks generated and thereafter keep propagating due mainly to the stress redistribution induced by excavation.In this study, an expanded distinct element method (EDEM) was developed for simulating the crack generation and propagation due to the shear and tension failures in the matrix rock blocks. Using this method, excavation simulations of deep underground caverns have been carried out on the models with differing depths of cavern and differing geometrical distributions of the existing discontinuities. Model experiments by using the base friction test apparatus were conducted to verify the proposed numerical approach. Furthermore, the support effects of rock bolts on controlling the deformations of the rock mass surrounding a cavern and movements of key blocks were evaluated by means of the EDEM approach.