强震诱发拉裂-滑移型滑坡的瞬态超低摩擦启动机理

The initiation of a landslide induced by massive earthquake is a complex and severe shatter-failure process, which significantly influences the landslide mode and even its kinematic process. Many special dynamic failure phenomena triggered by Wenchuan earthquake have shown that the rip-slide landslide initiation induced by massive earthquake appears the transient ultra-low friction effect. In view of a lack of deeply understanding the mechanism of this effect now, taking Wenchuan earthquake as research background, by means of experiment and theory research methods and numerical simulations, the applicant and his groups intend to study the initiation mechanism of transient ultra-low friction for rip-side landslide induced by massive earthquake. Firstly, the dynamic response of massive earthquake-caused shatter-damage of the sliding surface will be studied, which aim to reveal the micro-meso-macro multi-scale shatter-damage evolution of the sliding surface under the action of P seismic wave and time difference coupling effect of P and S seismic waves respectively. Under the coupling influence of shatter-damage and normal stress fluctuations at the sliding surface, the dynamic attenuation models of sliding resistance and friction are established. Then, for stratified rock slope and three typical rip-slide landslides induced by Wenchuan earthquake (the Donghekou landslide in Qingchuan, Tangjiashan landslide in Beichuan and Daguangbao landslide in Anxian county )，the landslide initiation mechanism triggered by time difference coupling influence of P and S seismic waves will be studied. The dynamic response of stress, deformation, acceleration and acoustic emission near the sliding surface and crown tensile surface can be revealed. Finally, based on the understanding of the kinetics mechanism of landslide initiation of transient ultra-low friction, the kinetic theoretical model of landslide initiation will be established. The future research results will enrich innovatively the basic theory of earthquake-caused landslide mechanism.

强震诱发滑坡启动是一个非常复杂且剧烈的震裂破坏过程，其对滑坡模式甚至运动过程等均有重要影响。汶川地震较多特殊动力破坏现象表明强震诱发拉裂-滑移型滑坡启动具有瞬态超低摩擦效应。鉴于当前缺乏对这一效应机理的深入认识，以汶川地震为背景，采用试验、理论研究及数值模拟等方法，开展强震诱发拉裂-滑移型滑坡瞬态超低摩擦启动机理研究。首先研究强震致使滑动面震裂损伤的动力响应，揭示纵波、纵-横波时差耦合作用下滑动面的微-细-宏观多尺度震裂损伤演化，建立滑动面震裂损伤-法向应力波动耦合效应下抗滑阻力及摩擦力动态衰减模型。继而研究纵-横波时差耦合作用下顺层斜坡和典型滑坡（青川东河口、北川唐家山及安县大光包）拉裂-滑移启动过程机制，揭示滑动面及后缘拉裂面附近应力、变形、加速度及声发射等动力响应特征。最终在揭示滑坡启动瞬态超低摩擦动力学机理的基础上，建立其动力学理论模型。研究成果将创新性丰富地震滑坡机理的基础理论。

汶川地震等强震触发的滑坡成因机制十分复杂，具有与通常重力环境下斜坡失稳机制迥异的特征。其中，最为显著的特征是许多大型滑坡滑动面首先被震裂（张性破裂为主），然后高速滑动甚至抛射。针对强震所触发的滑坡张性破裂及低摩擦启动这一动力学机制，采用工程地质分析、室内岩石力学试验、高速旋剪试验和振动台试验等手段，结合地震动力学、岩石力学、摩擦力学和运动学等理论，对强震触发滑坡基本特征及破坏机制、岩层面等结构面动态拉伸和拉剪力学特性及强度准则、节理面及滑动面动态摩擦特性及滑动摩擦准则、滑坡震裂-启动动力学模型、孔隙水压力的形成机制及数学模型、抛射体飞行时空气动力学效应和撞击解体机制等从理论到实例应用进行了较为系统的研究，主要研究内容和成果如下：.①对岩体结构面开展了三种动态直接拉伸试验，揭示了加载速率及循环荷载频率对结构面强度的影响。.②发明了一种可在压剪试验机上使用的岩石拉剪装置，基于动态的直接剪切试验结果，建立了岩体结构面拉伸-拉剪-压剪统一强度准则。.③基于振动台滑块试验结果，建立了随滑动速率增加摩擦系数初期增大-随后弱化的速率依赖性滑动摩擦准则。.④提出了考虑震裂阶段和启动滑移阶段全过程的地震滑坡动力学分析概念。通过对剩余推力法进行改进并编制了计算程序对算例进行了纵横地震波时差和相位差耦合动力分析。.⑤基于节理动态循环剪切试验、高速旋剪试验和环剪试验的结果，得到了节理和滑动面动态摩擦衰减的模型及孔隙水压力模型，并将其嵌入到DDA代码。模拟结果表明，节理和滑动面摩擦系数的衰减及孔隙水压力的升高，都促使滑坡速度和运动距离的增大。.⑥分析空气动力效应对滑坡抛射体飞行过程的影响表明，作用于抛射体上的水平向推动力及竖直向的擎托力，共同导致了抛射体更长的飞行时间和更大的运动距离。.研究成果在地震滑坡机理、灾害预测及风险控制方面具有较好的理论价值及应用前景，并推动了岩体动力学的发展。