Research purposes:Because that most of the advanced geological prediction of tunnel seismic reflection method is based on 2D prediction and the accuracy is not high, an effective observation method of advanced geological prediction of three-dimensional seismic reflection is proposed. On this basis, a complete set of technology research on data processing and imaging is carried out, and its feasibility and reliability are verified through numerical simulation and physical experiments, which is effectively applied to the production of advanced geological prediction of railway tunnel.
Research conclusions:(1) Based on the basic theory of elastic wave, a three-dimensional seismic wave advance geological prediction observation system based on shear wave is proposed. Compared with the traditional P-wave prediction method, it has higher resolution and is more sensitive to water body. (2) The migration imaging method based on Kirchhoff integral is realized, which uses the energy superposition criterion for three-dimensional velocity scanning, and uses the fast marching method for travel time calculation, which is not limited by the observation system, has high calculation efficiency, and do not need a very accurate velocity model. (3) The finite difference numerical simulation of three-dimensional seismic wave field of tunnel is realized, and the typical adverse geological models such as lithologic interface with different dip angles, faults with different thickness and karst caves with different diameters are established, and their three-dimensional imaging characteristics are analyzed and summarized. (4) Through the physical model and application experiment, the method presented in this paper is feasible and reliable, and can be popularized and applied in tunnel advanced geological prediction.