Two-dimensional numerical simulation of tunnel-based seismic full-wave fields

The two-dimensional (2D) numerical simulation of seismic wave fields based on tunnels is a basis for the analysis of propagation laws of seismic waves in the tunnel prediction. All of the current researches, which are designed with observation systems on the sidewalls of tunnels and assume tunnels as homogeneous media with the same elastic parameters of surrounding media, are not in conformity with the actual situations because they cannot involve surface waves. A geological tunnel-based model is established, which is more suitable for the practical tunnels to achieve the 2D numerical simulation of seismic full-wave fields. The results show: (1) using a staggered grid finite-difference (FD) algorithm with a second-order accuracy in time and a fourth-order accuracy in space, we can achieve the 2D numerical simulation of seismic full-wave fields without ignoring the air medium in tunnels; (2) when considering a vertical geological interface, common-source system with shots near the tunnel face is better for obtaining reflection waves than the one with shots on the side walls; (3) with the decrease of the dips of geological interfaces, the energy of reflection waves increases when shots and receivers are on the same side; (4) for the local geological features and interfaces, shear wave shot on the tunnel face, which acquires more energy than pressure wave shot, can help in shear wave imaging.