Techniques for Progressive Failure Simulation of Hard Brittle Surrounding Rockmass: Taking the URL Test Tunnel as an Example

Abstract

Accurate simulation of the failure process of hard brittle surrounding rockmass is very important for the analysis and control of the structural stability in deep underground engineering. In order to simulate the progressive failure process of the hard brittle surrounding rockmass, a continuous discontinuous deformation analysis method that couples the finite element and discrete element is adopted. Taking the URL test tunnel in Canada as an engineering case, the constitutive model of the contact considering the effects of cohesion weakening and friction strengthening is applied, and the 2D approximation to 3D excavation by applying elastic modulus reduction technology is adopted to simulate the range and depth of crack growth of the surrounding rockmass. Then, the comparison between simulated results and on-site monitoring results is performed, which shows good consistency. At the same time, the key factors in the numerical simulation of progressive failure in hard brittle rockmass are identified, including the number of elements, excavation effects, and constitutive models. The results show that the constitutive model determines the basic form of crack propagation, but in order to accurately simulate the progressive propagation of cracks, the number of elements must be sufficient enough and the effects of 3D excavation must be considered. The analysis accurately simulates the progressive failure characteristics of hard brittle surrounding rockmass under high stress, achieving the purpose of reasonably grasping the degree of damage to the surrounding rockmass, and provides technical reference and support on how to accurately simulate the failure of hard brittle surrounding rockmass using the finite discrete element method.

Progressive Failure of Surrounding Rock in Underground Engineering and Size Effect of Numerical Simulation

“…In the paper about URL test tunnel [19], the key factors of crack propagation simulation using the continuous discontinuous analysis method are discussed, including size efect, constitutive model, and excavation method. Te results show that the constitutive model determines the basic form of crack propagation, but in order to accurately simulate the progressive propagation of cracks, the number of elements must be sufcient enough, and the efects of 3D excavation must be considered.…”

“…Based on the advantages and adaptability of the continuous method and discontinuous method, numerical methods combining continuous and discontinuous medium method (such as FEM/BEM, FEM/DEM, and FDM/DEM) are gradually developed. Among them, the coupling method of the fnite element and discrete element is the most mature, and many achievements have been made [19][20][21][22]. For example, the author uses the CDEM method to simulate the progressive failure of the surrounding rock of Canadian URL test tunnel [19] and Baihetan exploration tunnel [18].…”

“…Among them, the coupling method of the fnite element and discrete element is the most mature, and many achievements have been made [19][20][21][22]. For example, the author uses the CDEM method to simulate the progressive failure of the surrounding rock of Canadian URL test tunnel [19] and Baihetan exploration tunnel [18]. Besides, the coupling of fnite element methods and peridynamics [23][24][25] also developed to solve similar problems.…”