关键词: 隧道超前探测, 地震波场模拟, 数值计算, PML吸收边界

Abstract: The purposeof seismic numerical forward modeling is to provide good simulation data for tunnel advanced detection and evaluate the accuracy and stability of inversion. However, the direct use of numerical simulation methods used in surface exploration will lead to a series of problems, such as slow calculation speed, poor boundary absorption effect and serious dispersion. In this paper, a forward simulation method for tunnel advanced detection is proposed, which includes solving the first-order velocity stress elastic wave equation with high-order staggered grid finite-difference method to obtain wave field information at any time, selecting suitable mesh accuracy and difference order satisfying stability conditions, using PML (Perfectly matched layer) absorbing boundary of new attenuation function to deal with reflection problem caused by artificial boundary, and using staggered grid and FCT(Flux Corrected Transport) method to suppress dispersion. Finally, this paper establishes the inclined layered tunnel model and the cavity tunnel model in heterogeneous media, simulates the above methods, and obtains clear wave field and gather data, which proves the feasibility of the forward modeling method in this paper.

Key words: Tunnel advance detection, Seismicwave field simulation, numerical calculation, PML absorption boundary