散粒体边坡的倒塌破坏及其内部变形的物理模拟研究

Flow-like mass movement is the most destructive landslide and causes loss of lives and substantial property damage throughout the world every year. Those slope movements, which have long travel distance, high velocity and large volume of failure mass, are the most difficult to prevent. As such, it is of great significance to understand the kinematics and dynamics of the flow-like mass movement of granular materials. Many researchers have been studying the problem of the granular mass movement, where most of the focus has been on the run-out distance analysis and/or the triggering and motion mechanisms of flows. However, few investigations have been carried out on the kinematics and internal deformation of the granular slopes. Previous studies of the applicant show that the collapse of granular slopes results in different-generation extensional faults in the back of the slope, and contractional structures (overturned folds, sheath folds and thrusts) in the toe of the slope. This project uses results from analogue models to investigate the kinematics and internal deformation structures during the collapse of granular slopes. The models simulate the collapse of granular slopes and focus on the spatial and temporal distribution of their internal structures. This project also studies the effect of the slope height, slope angle, internal friction angle of the granular material, particle size and particle size distribution of the granular material on internal deformation within a granular slope.

散粒体滑坡运动速度较快，产生的位移较大，内部变形极其复杂，是滑坡最为复杂的运动模式，每年给当地环境、人民生命和财产安全造成不可估量的损失，已经成为近年来的研究热点。大多数研究的重点是滑动距离和边坡倒塌破坏诱发机理，然而在滑体的运动学机理及其内部变形方面的研究有待于进一步深入。申请者在前期研究中发现散粒体边坡的倒塌破坏诱发了边坡背部不同期次的伸展断层的形成，以及坡脚部分压缩构造（倒转褶皱，鞘褶皱和逆断层）的产生。本课题拟采用构造地质砂箱模拟试验的方法来深入研究散粒体滑坡滑体的运动学机理和内部变形，揭示散粒体边坡滑体内部不同期次的伸展断层和复杂褶皱变形的时空演变规律，探明散粒体材料颗粒的几何属性及其剪切强度、边坡高度(尺寸效应)、边坡坡角等对散粒体边坡运动与内部变形的影响。本研究课题为治理散粒体滑坡问题提供重要的理论依据，防止或降低滑坡发生时造成的各种损失。

滑塌构造往往是由于古斜坡发生滑塌后形成的，它是自然界中极其重要的一种地质构造。滑塌构造变形中有重要的“指向”意义，可以用于恢复古地理环境（古地形起伏方向），揭示盆地古斜坡方向。近年来对滑塌构造的研究越来越受到重视，然而，大部分有关滑塌构造的模拟研究至今仍然很少，对滑塌构造的产生缺乏一个系统的认识。本项目通过一系列的砂箱模拟实验，针对散粒体滑坡滑体的运动学机理和内部变形过程开展了相关基础研究。滑塌构造在边坡的背部形成一系列的不同期次的正断层；在滑塌体的前端形成了倒转褶皱、逆断层、鞘褶皱等压缩构造；同时，滑塌体内部存在小型断裂和角砾化以及不同滑塌层的混杂现象。滑塌体沿着不同期次的正断层滑塌，先期的滑塌面倾角较陡（60度），滑体体积较大；后期的滑塌面倾角较缓（40度），滑塌体体积较小。砂箱模拟实验不仅对滑塌构造的产生、滑体背部的断裂面，前方的压缩构造区进行了系统地研究，还解释了滑体内部不规则角砾区的发育机理。实验结果与软沉积滑塌构造进行对比研究，很好地解释了滑塌构造背部断裂区与前方压缩构造区的变形机理。通过系统地改变散粒体边坡坡角、边坡高度（尺寸效应）、散粒体材料的内摩擦角、软弱层的存在及其几何属性等参数，研究了这些因素对软沉积物滑塌运动学机理及其内部变形的影响。这些因素不仅影响了滑塌构造正断层与压缩构造的分布规律，同时还影响了不同期次断层的断距及其倾角、滑体的最大滑动距离和休止角等。