基于地球物理方法的红土型滑坡地质结构特征及变形演化机制研究

The hydrogeological structural of landslide, the geometry and depth of the slip surface, the deformation evolution characteristics are very important basis of landslide mechanism, stability analysis, protection and governance.Yunnan laterite-type landslide is a special kind of clay landslide，geophysical parameters carry landslide geomechanical behavior information during the preparation development of the landslide,but lack of quantitative interpretation methods and techniques.This research intends to probe 3D geological structure using multiple geophysical techniques, further develop positioning method of sliding surface or zone based on fuzzy sets theory with the technical existing resolution. Meanwhile, We design consolidated oedometer bender elements test system to build the relationship between shear wave velocity, electrical resistivity and physical and mechanical property of slip zone laterite. From the microscopic point of view, deformation evolution characteristic, Shear behavior and influence factors of slip zone laterite will be discussed by aid of scanning electron microscope. Combined with landslide deformation monitoring data, integrate multi-stage surface wave, time-lapse electrical resistivity tomography and numerical simulation to replay landslide deformation evolution process under rainfall condition,illustrate the deformation development features and rainfall infiltration, migration rule in the landslide body, reveal the deformation evolution model and mechanism of laterite-type landslide. The study was expected to provide a new idea for the formation mechanism further study and the theoretical basis for the landslide disaster prevention and governance work of laterite-type landslide.

滑坡水文地质结构特征和滑动面的几何形态、埋深及滑坡变形演化特性是滑坡形成机理研究、稳定性分析和预警防治的重要依据。云南红土型滑坡是一种特殊的粘性土滑坡，在滑坡孕育、发展过程中，地球物理参数携带滑坡地质力学行为信息，但缺乏定量化的解译方法和手段。本项目拟通过多种地球物理技术探测红土型滑坡三维地质结构，在技术现有分辨率基础上，发展基于模糊子集理论的滑动面（带）定位方法；同时设计固结试验弯曲元测试系统，建立滑带红土剪切波速、电阻率与其物理力学性质的关系，借助电子扫描电镜从微观角度研究滑带红土的变形演化特征、剪切行为及影响因素；并结合滑坡变形监测资料，采用多期面波、电阻率时移监测和数值模拟手段，重构降雨作用下滑体的变形演化过程，综合阐明滑坡变形发育特征和坡体内降雨入渗、运移规律，揭示红土型滑坡变形演化模式和机制。该研究将为深化红土型滑坡形成机理认识提供新思路，并为红土型滑坡防治工作提供理论依据。

云南地区地质构造复杂，红土层广泛分布，伴随山区水电、交通等基础设施建设，产生大量的红土型边坡，地震、降雨和工程活动常导致红土型滑坡的孕育和发生。以云南省寻甸县甸头村滑坡为例，综合地球物理探测技术（瞬态面波法、高密度电法和地质雷达法）获取滑坡地质结构特征，结合现场工程地质勘察、监测资料及室内土力学试验和数值模拟手段，揭示红土型滑坡的地质结构特征及其变形演化模式与机制。研究结果如下：（1）地球物理层析成像技术能便捷获取滑坡体的地质结构特征，采用模糊子集理论融合方法显著提高地球物理反演结果的解译精度，实现红土型滑坡滑动面（带）的定位分析；（2）提出基于临界位移等值线的多阶边坡多级滑动面搜索方法、基于改进生物地理学算法的均质土坡滑动面搜索方法和考虑含水率变化影响的红黏土边坡双强度折减法，地球物理技术与数值搜索方法融合运用为滑坡工程勘察设计提供新手段；（3）通过室内三轴弯曲元测试系统、改进的压缩固结电阻率测试仪，模拟滑带红黏土变形中剪切波速、电阻率的变化规律，建立红黏土剪切波速的剪切强度评价模型、固结压缩电阻率模型；提出考虑红黏土颗粒形状及矿物成分影响的红黏土有效介电常数理论模型；（4）红黏土固结压缩过程中地球物理参数（剪切波速、电阻率）随物理力学指标（含水率、剪切强度）呈现出规律性变化，可用于间接评价坡体变形演化滑带红黏土的压缩、剪切特性，为红土型滑坡地球物理监测预警深入研究提供新思路；（5）结合监测资料、渗流-应力耦合条件下坡体变形演化模拟可知，红土型滑坡入渗集中于浅层，深部滑移取决于地形地貌及下覆地层岩性，红土层起到了入渗“阻隔”作用，饱和度、孔隙水压力增大导致红黏土层土体强度降低，表现为“浅层入渗饱和、局部崩塌—后缘拉裂、前缘蠕动—潜在多级滑动带形成—滑动面贯穿滑移”变形演化模式。该研究为地球物理技术应用于红土型滑坡的稳定性评价分析、监测预警和防治工作提供理论依据和技术支撑。