Abstract
In order to study the damage effect of blasting load on the surrounding rock of shallow-buried small spacing twin tunnels, the shallow-buried tunneling section of the south extension project of Shunhe Expressway is taken as the engineering background. Firstly, based on the dynamic damage evolution and Hoffman failure criterion, an anisotropic dynamic damage constitutive model for rock materials is established. Then, by using the secondary development function of the LSDYNA software, the constitutive model is applied to the numerical simulation of the tunnel blasting damage. Finally, based on the acoustic wave measurement theory, the wave velocities in the surrounding rock of the shallow-buried small spacing twin tunnels before and after blasting were measured by using non-metallic ultrasonic detectors, and the damage of the surrounding rock is evaluated from changes in wave velocity. The applicability of the anisotropic dynamic damage constitutive model and the accuracy of the numerical results are verified by comparing the numerical simulation results with the field test results. The numerical simulation results show that the maximum damage radius of single-hole blasting is 0.58 m, and the maximum damage depth is 1.88 m. According to the damage threshold of the rock mass, the horizontal failure range of the rock mass can reach 0.14 m, and the failure depth is 1.70m. According to the field test, the damage degree of the middle intercalated rock is higher than that of the other parts of the surrounding rock in the alternate blasting excavation of the double track tunnel. The damage depth of the surrounding rock caused by blasting excavation is about 0.5 m, which is close to the simulation results, and verifying the accuracy of the anisotropic dynamic damage constitutive model. The research results have a certain guiding role on the blasting excavation and damage control of shallow-buried twin tunnels with small spacing..
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