强震诱发岩质滑坡滑动面破裂贯通机制研究

Fracture propagation and coalescence of slip surface is considered as the intrinsic mechanism of the progressive deformation and failure of slopes. Based on the field investigation on Wenchuan Earthquake induced landslide, large-scale slope slides occurred mainly in rock slopes, with special slip surfaces and complex dynamic fracturing processes, and no systematic research on its physical mechanism has been carried out. A comprehensive study will be conducted in this project with theoretical analysis, physical model tests, numerical calculations and combined tension and shear test. A mathematical dynamic model of slope affected by seismic waves will be proposed. The shaking table tests on physical models will also be carried out and the fracturing process of the slip surfaces will be recorded by high speed camera. Thereafter the numerical model will be built with PFC (Particle Flow Code) to analyze the dynamic process of crack initiation stress, position, propagation patterns, as well as failure types with the seismic wave propagation, and the spatial-temporal evolution from micro crack initiation, propagation to formation of macro slip surfaces will be obtained. Based on the analysis of the mechanism and the dominated factors related to the process of micro crack propagation and formation of macro slip surface in the slopes with different configurations, geological structure, seismic load, etc., physical mechanism of earthquake-induced landslide will be studied.

滑动面的发展贯通过程是边坡变形破坏发展过程内在机制的体现，是从本质上认识边坡变形破坏的基础。汶川震后调查发现，大型滑坡多为岩质滑坡，滑动面形态独特，其破裂贯通的动力学过程极其复杂，对其物理机制尚未有系统的研究。本项目拟采用理论分析、物理模拟、数值模拟和拉剪试验相结合的方法，通过理论分析建立地震波波动作用下的边坡动力学模型，开展振动台物理模型试验利用高速摄像技术等多种手段记录滑动面破裂贯通过程，在此基础上采用数值分析和拉剪试验相结合，获取并验证地震滑坡孕育过程中边坡内部破裂的应力状态、起裂位置、破裂类型、扩展形态和贯通模式随地震波传播的动态变化，进而得到准确的边坡内部新旧裂纹扩展贯通形成宏观滑动面的时空发展贯通过程。通过改变边坡坡形和地震荷载输入，分析在地震波波动作用下边坡内细微裂纹扩展贯通形成宏观滑动面的物理机制和控制因素，揭示强震诱发新生岩质滑坡的物理机制。

项目在理论分析的基础上，选择汶川地震区典型地震斜坡变形体，开展了物理模拟试验和数值模拟试验。根据试验得到的规律性认识，对规则边坡的变形特征与输入地震波之间的关系进行了深入研究，通过研究发现：1）斜坡已有结构面对滑动面的破裂贯通有控制作用，地震滑坡的滑动面多沿已有层面扩展贯通形成，无明显结构面的斜坡仅发生浅层破坏；2）地震波频谱特征对斜坡变形破坏范围和破坏形式具有决定性作用，地震波频率越低，斜坡的变形破坏范围越大，但变形破坏所要求的峰值加速度也越大，地震波频率越高，斜坡变形破坏范围越小，但更容易造成浅表层破坏；3）坡度30°-50°的斜坡较容易发生滑动破坏，且坡度较小时坡表顺层滑动现象明显，坡度较大时坡体内部损伤较大，坡顶更容易发生拉裂缝和永久损伤；4）斜坡变形破坏过程中坡顶为拉裂破坏、坡脚处于剪切破坏，坡体内已有结构面多为剪切破坏，只在陡倾结构面内发生拉剪破坏；5）斜坡坡脚处岩体结构及强度对斜坡变形破坏范围具有重大影响，斜坡坡脚不存在软弱岩体或结构面时，坡顶拉裂缝难以发展贯通形成滑动面。