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.
The analysis and simulation of brittle failure of hard rock tunnels under high stress is essential for understanding and mastering the brittle failure characteristics of rock masses and for analyzing and regulating the stability of surrounding rocks in underground projects. The rupture and deformation of hard brittle basalt in the dam site area is one of the key problems faced by Baihetan Hydropower Station. In the paper, the spalling characteristics of the surrounding rock on the right bank of the exploratory tunnel are summarized. CDEM (continuum-based discrete element method) is used to carry out the numerical simulation and the fracture energy model considering cohesive force weakening and friction angle strengthening is adopted. The indoor test simulations are conducted first to verify the effectiveness of the model. Then the simulation of the right bank exploratory tunnel is conducted to study the brittle failure of the surrounding rock. The results are compared with the field exposure, and the stress and displacement of characteristic points of the surrounding rock are analyzed. The numerical results are in good agreement with the damage situation in the field and reflect the brittle failure characteristics of basalt under high-stress conditions, which helps to reasonably grasp the damage situation of the surrounding rock and take corresponding support measures, and also proves the superiority of CDEM method in solving hard rock fracture, providing a technical reference for similar hard rock brittle failure problems in engineering.
The analysis and simulation of progressive failure of surrounding rock is very important for analyzing the stability of surrounding rock in underground engineering. Size effect is also a key problem worth further study in engineering. Taking the underground powerhouse on the right bank of Baihetan as an example, the acoustic test results are collected and the relaxation and failure characteristics of the surrounding rock are summarized. Then, the numerical simulation of progressive failure of surrounding rock of underground powerhouse is carried out by using the finite discrete element method CDEM (continuum-based discrete element method). The results are compared with the acoustic test results of the surrounding rock relaxation layer, and the stress and displacement of surrounding rock characteristic points are analyzed. At the same time, the size effect of grid and mechanical parameter in the process of numerical simulation are discussed. The calculated fracture depth of surrounding rock is in good agreement with the acoustic test results, which shows the reliability of progressive failure simulation of surrounding rock of the underground powerhouse. When CDEM is used to simulate the excavation of tunnels with different tunnel diameters, the minimum grid size should be about 1% of the tunnel diameter. The mechanical parameters of rock mass have significant size effect, which needs to be analyzed in detail. The research results prove the superiority of the CDEM method in simulating the progressive failure of hard surrounding rock and its unique size effect characteristics, which can provide technical reference for the application of the CDEM method in other similar engineering problems.
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