库岸含砾滑带土的变形、强度特征与砾-土相互作用机制研究

The research object of this project is gravel-bearing slip soil which has certain representativeness on Three Gorges Reservoir Area. By analyzing the effect of periodic changes of the reservoir water level on the engineering geological environment of the sliding zone, the characteristics and its evolution law of effective stress field, moisture field and temperature field can be obtained. With CT scan and digital image processing technologies, characteristics of gravel fabric in the slip soil is described. By using large scale triaxial test, creep test and numerical simulation methods, we can get the deformation, the strength characteristics and creep properties of gravel-bearing slip soil. The experiments and simulation will be performed with the consideration of the fluctuation of reservoir water level, that is to say the moisture content, confining pressure and temperature will be changed individually and couplingly. The creep model of gravel-bearing slip soil can be established according to the experimental results. Combined with numerical simulation methods, gravel - soil deformation mechanism and movement law of gravel will be explored, and gravel - soil interaction processes and mechanisms during the slip zone deformation process can be revealed also. The experimental results can provide a good understanding of landslide mechanisms under the conditions of reservoir operation.

本项目以三峡库区分布具有一定代表性的含砾滑带土为研究对象，通过分析库水位周期变动对滑带工程地质环境的影响，得到滑带有效应力场、水份场和温度场的分布特征和变化规律；通过CT扫描和数字图像处理技术，描述含砾滑带土的砾石组构特征，模拟库水位周期变动条件，采用大三轴试验、蠕变试验以及数值模拟方法研究含水率、围压、温度单一因素和多因素耦合作用下不同砾石组构特征含砾滑带土的变形、强度特征和蠕变特性，建立含砾滑带土的蠕变模型；结合数值模拟方法，探索含砾滑带土砾-土变形机理及砾石的空间运动规律，揭示滑带变形过程中砾-土相互作用过程及机制，为正确认识水库运行条件下滑坡活动机理提供依据。

在自然界中，广泛分布着一类粗、细颗粒混杂，具有一定含石量、极端不均匀的松散地质体，导致了其物理力学性质非常复杂。该地质体以砾石（块石）为骨料，其含量、粒度、空间分布等组构特征对这类地质体的性质影响非常显著。三峡库区马家沟滑坡滑坡体主要由坡积形成的粉质粘土夹碎块石构成，砾石或者碎石的含量约为20%~30%，直径约为2~100mm，因其滑带发育在基岩界面和松散层内，故含砾。本项目以马家沟含砾滑带土为研究对象，通过建立分布式光纤监测系统，对库水位周期变动条件下滑带工程地质环境的变化进行监测，得到了滑坡体的变形、应力、水份和温度等多场多参量的分布特征和演化规律，建立了滑坡数值计算模型，为含砾滑带土室内试验和数值模拟试验提供依据。根据滑带的物质组成和砾石的组构特征，制作了三轴剪切试样，通过试验得到了不同含石量土体的变形、强度特征。通过三轴蠕变试验和三轴应力松弛试验研究了含砾滑带土的流变特征，建立含砾滑带土的流变模型。提出了砾石组构的三维数字化重建方法，利用CT扫描和数字图像处理技术，得到了含砾滑带土试样内部砾石的粒度组成、形态、轮廓和空间分布等组构特征。基于几何不变性，实现了对不同状态下砾石的识别，提出采用迭代最近点算法，对砾石进行空间配准，得到了三轴剪切过程中砾石的空间运动和姿态的变化。同时，根据CT影像建立了FLAC3D和PFC3D数值计算模型，对砾石的运动和砾-土的相互作用进行了模拟，分析了砾石组构特征对剪切带发育的影响，揭示了滑带变形过程中砾-土相互作用过程及机制，为正确认识水库运行条件下滑坡活动机理提供了依据。