Assume that we are going to construct 5 mx 5 m mine access tunnels at the depth of 1000 m, and we need to analyze stress and deformation for tunnel design. The rock density is 2700 kg/m! The vertical in situ stress is induced by gravity and the horizontal stress is 1.4 times higher than the vertical stress. The average uniaxial compressive strength of the rock is 220 MPa, and the average crack initiation stress determined from lab test is 85 MPa. The Young's modulus and Poisson's ratio of the intact rock are 50 GPa and 0.2, respectively. The mine access tunnels will pass through rock mass zones with peak GSI values of 80 and 70. Very careful drill-and-blasting will be conducted to minimize excavation-induced damage to the rock mass. (a) Use RS2 to analyze the excavation behaviors (eg, depth of failure, wall deformation) of the tunnel based on the rock mass mechanical properties determined from the GSI system. Compare the results of the perfectly plastic model with that of the plastic model considering residual strength The residual strength can be estimated from the GSI system. (b) Compare the results of sudden excavation with that of gradual excavation (c) Compare the results of flat roof with that of arched-roof. Assume that we are going to construct 5 mx 5 m mine access tunnels at the depth of 1000 m, and we need to analyze stress and deformation for tunnel design. The rock density is 2700 kg/m! The vertical in situ stress is induced by gravity and the horizontal stress is 1.4 times higher than the vertical stress. The average uniaxial compressive strength of the rock is 220 MPa, and the average crack initiation stress determined from lab test is 85 MPa. The Young's modulus and Poisson's ratio of the intact rock are 50 GPa and 0.2, respectively. The mine access tunnels will pass through rock mass zones with peak GSI values of 80 and 70. Very careful drill-and-blasting will be conducted to minimize excavation-induced damage to the rock mass. (a) Use RS2 to analyze the excavation behaviors (eg, depth of failure, wall deformation) of the tunnel based on the rock mass mechanical properties determined from the GSI system. Compare the results of the perfectly plastic model with that of the plastic model considering residual strength The residual strength can be estimated from the GSI system. (b) Compare the results of sudden excavation with that of gradual excavation (c) Compare the results of flat roof with that of arched-roof
