【摘要】 本文基于二维有限元数值方法,模拟了复杂条件下隧道内的地震全波波场,分析了隧道地震超前预报中的反射记录中的多方向和多波反射波特征,证实了分离前方有效反射波和其它方向的干扰反射波,以及有效反射波的P波、S波分离在预报准确性中的重要性.基于多个数值模型,研究了τ-p变换进行波场分离的有效性和影响因素.研究结果表明:在隧道前方反射层倾向与隧道轴线交角变化较大范围内(90°～45°),τ-p变换都可以有效的分离多方向和多波反射事件,提取主要来自掌子面前方的有效反射波剖面.来自隧道顶、底的缓倾界面的具有双曲时距曲线特征的干扰波和S波的高视速度会对P波的波场分离产生较大干扰;而由于S波的低速和强能量特征,其波场分离受具有双曲时距曲线特征的干扰波的视速度影响较小,且不受P波的影响.更多还原

【Abstract】 This article presents the simulation of tunnel seismic wave field under complex conditions by using the finite element method.The importance of the separation of interested reflected seismic wave ahead of tunnel face from other directions and that of interested P-wave and S-wave are showed based on the characteristic analysis of the multi-directions and multi-components of the reflection records.in tunnel seismic records,Based on several numerical models,the flexibility of the τ-p transformation for the wave field separation are studied and the results show that τ-p transformation is effective in the separation of the multi-directions and multi-components of the reflection records from the wave ahead of tunnel face,even if the dips of reflector ahead of tunnel are varying widely(90°~45°).Because of the high apparent velocity effects due to the interference waves with hyperbola time-distance relationship and S-wave,the separation of interested S-wave is usually clearly,whereas that of P-wave has more interference waves.Therefore,in the subsequent processing,it should be separated as the main basis for S-wave profile.For the angle of reflection layer <45°,due to its time-distance relationship is not linear relationship,the difference between the designed filter of apparent velocity which based on the linear relationship of the direct wave and actual relationship is too large for pressure or shear waves,therefore errors of separation are large,so adopted migration processing before the τ-p transformation for the flat dipping fault.更多还原