基于射线理论的垂直P波入射过程滑坡滑带应力放大特征及成因分析  

Stress amplification of the landslide slip zone during vertical P-wave incidence based on ray theory

作　　者：雷津 崔圣华 裴向军[1] 杨海龙 朱凌[1] 杨晴雯[1] Lei Jin;Cui Shenghua;Pei Xiangjun;Yang Hailong;Zhu Ling;Yang Qingwen(State Key Laboratory of Geohazard Prevention and Geoenvironment Protection,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]成都理工大学地质灾害防治与地质环境保护国家重点实验室,成都610059

出　　处：《地质科技通报》2022年第6期149-161,共13页Bulletin of Geological Science and Technology

基　　金：国家自然科学基金项目(41931296,41907254);国家重点研发计划项目(2017YFC1501002)。

摘　　要：汶川地震触发的最大滑坡——大光包滑坡是受控于斜坡先期层间构造错动带(软弱层)的大型地震滑坡,该软弱层不但遭受了强烈的历史构造碎裂,还在地震中产生了大面积新生震裂,其成因及对大光包滑坡启动的贡献一直是国内外研究焦点。以大光包滑坡为地质原型,将层间构造错动带概化为含软弱层单元地质体模型,基于地震波射线理论,建立了垂直P波入射过程考虑软弱层顶底界面波场转换和时间延迟的动力响应理论模型,开展了垂直振动作用下含软弱层单元地质体振动台模型试验,获得了软弱层应力放大特征及受地震强度和频率的影响规律,揭示振动波在软弱层顶底界面的波场转换和能量分配产生了振幅衰减,以及因软弱层与上下硬层介质属性差异造成的时间延迟,共同导致应力分异和叠加,促使软弱层应力放大;从而认为,强震过程中大光包滑坡先期层间构造错动带应力放大导致了带内岩体碎裂,降低了滑带岩体抗剪强度,从而促使强震过程中滑坡快速启动。The largest landslide triggered by the Wenchuan earthquake was the Daguangbao landslide,which formed in the preinterlayer structural dislocation zone(weak layer)in the slope.The weak layer suffered strong historical structural fragmentation and produced a large area of new fractures during the earthquake.The causes of weak layer fragmentation and its control effect on the initiation of the Daguangbao landslide have always been the research focus.In this paper,by taking the Daguangbao landslide as the geological prototype,the interlayer dislocation zone was generalized into a geological body model with a weak layer unit.Based on seismic wave ray theory,a dynamic response theoretical model of the vertical P-wave incidence process considering the wave field conversion and time delay at the top and bottom interface of the weak layer was established,and the dynamic stress amplification characteristics of the weak layer are found theoretically.Furthermore,through a shaking table physical model test,the influence law of seismic intensity and frequency on the stress amplification of the weak layer were revealed.Based on the theory and experimental structure,it was proposed that the amplitude attenuation was caused by the wave field conversion and energy distribution of the vibration wave at the top and bottom interface of the weak layer,and the time delay was caused by the difference in the medium properties between the weak layer and the upper and lower hard layers.Both of them lead to stress differentiation and superposition,which was the internal mechanism of stress amplification in the weak layer.Therefore,it was considered that the stress amplification of the preinterlayer structural dislocation zone of the Daguangbao landslide in the process of a strong earthquake led to the fragmentation of the rock mass in the zone,reduced the shear strength of the rock mass in the slip zone,and promoted the rapid start-up of the landslide in the process of a strong earthquake.

关 键 词：软弱层 射线理论 P波 延迟时间 应力集中 振动台试验 

分 类 号：P642.22[天文地球—工程地质学]