井巷工程反射波超前探测逆时偏移成像

探讨了井巷隧道工程反射波法超前地质预报成像问题.从一阶速度－应力弹性波方程出发，推导了二维各向同性介质情况下弹性波逆时传播的高阶差分格式，实现了弹性波在数值空间中的逆时延拓.构建反射波法隧道超前探测中的断层、软弱夹层等介质模型，以反射波探测的正演记录作为初始条件，并从程函方程出发，采用逆时差分格式求取介质模型网格空间中各点的直达波旅行时作为弹性波逆时偏移的成像条件，实现多波多分量资料的逆时偏移.偏移结果表明，逆时偏移能够使隧道壁接收到的波场准确归位，提高隧道反射波超前探测的资料处理的精度.

Reverse-time migration for detection ahead of mining tunnel by the reflection wave method in lane engineering

The paper discusses the imaging problem of detection ahead of mining tunnel by the reflection wave method in lane engineering. Based on one-order velocity-stress elastic wave equation, the high-order staggered grid finite difference scheme is established, which can achieve reverse-time propagation of elastic full-waves in 2D isotropic media. After two tunneling representative models with geological hazards in tunnels such as faults, a model of tilted weak interlayer in front of tunnel face is constructed, the synthetic records of detection simulation by reflection wave methods for those models are acquired, which were set as the original condition. Then by upwind finite-difference scheme of eikonal equation along expanding, wave fronts are used to calculate the minimum travel time of each grid point of those models called the excitation-time imaging condition in reverse-time migration. By these techniques, we have implemented the reverse-time migration of multi-wave and obtain multi-component information for those representative models. The results show that the algorithm can image the underground medium ahead of tunnel properly, and improve the precision of data procession.