基于黏弹性介质的隧道地震二维正演模拟

针对隧道中各种不良地质体的超前预报问题,以黏弹性介质为基础,在空气隧道周围添加一定厚度的开挖损伤带,建立符合实际情况的观测系统,通过交错网格有限差分正演,模拟地震波在断层、软弱夹层、溶洞等地质灾害体模型中的传播,根据不同时刻的波场快照来研究相应地质模型地震记录的响应特征。通过对隧道地震二维波场模拟结果进行分析,研究结果表明:对一阶速度-应力黏弹性波动方程,采用交错网格有限差分,并且对隧道添加约束条件,可以快速、有效地实现隧道地震的二维正演模拟,并且波场快照能够清楚地反映地震波在不同地质模型中的传播特征以及波的转换特征,地震记录能够反映不同地质模型的地震响应特征,可以为实际隧道超前预报提供理论依据。

Two-dimensional Forward Seismic Modeling for Tunnel Based on Viscoelastic Medium

In view of the problems in advanced detection of defective geological structures in tunnel,a geological tunnel model was established based on viscoelastic medium to simulate the seismic wave propagation in fault,weak interlayer,karst cave and other geological hazard body.The tunnel is surrounded by the excavation damaged zone. A practical observation system and the staggered grid finite-difference method were employed for the simulation. According to the wave field snapshots at different instants,the response of seismic record acquired from the corre-sponding forward modelling was researched.Result shows that the two-dimensional forward simulation based on vis-coelastic medium can be achieved by using a staggered grid finite-difference algorithm and adding tunnel con-straints.The wave field snapshots could clearly reflect the seismic wave propagation and transformation in different geological models.The seismic record reflects the seismic response characteristics of different models,and offers a theoretical basis for the seismic prediction of actual tunnels.