三峡库区具台阶状位移特征的堆积层滑坡变形机理研究

Colluvial landslide?with step-like deformation is one of the main geologic hazards during the operation of the hydropower station in the Three Gorges Reservoir,seriously threatening the lives and property of the people within their sphere of landslide influence and the shipping safety.?The geological environment of the reservoir of old or ancient colluvial landslide in the Three Gorges Reservoir is studied in detail through engineering geology investigation, especially slope structure of the lanslide and geologic structure of the sliding surface. Statistical analysis,mechanics analysis and engineering geology analysis are adopted?to study deformation characteristics of colluvial landslide?with step-like deformation on the basis of dynamic landslide monitoring imformation. The ring shear experiment and scanning electronic microscope experiment are used to study the variation law of shear strength，pore pressure and structure of sliding belt in different shear conditions, in order to explore the decay and growth characteristic of shear strength under the condition of landslide step-like deformation.The Bazimen landslide and Tangjiaocunyihao landslide in the Three Gorges Reservoir are taken as typical examples of colluvial landslide with step-like deformation.The numerical simulation method is adopted to simulate the evolution of landslide step-like deformation and study landslide reactivated conditions of old or ancient colluvial landslide with step-like deformation under the coupled function of water level fluctuation and rainfall througth the detailed analysis of seepage field, stress field and strain field. Spatial diversity of shear strength of the sliding surface is taken into account in the process of 3D numerical simulation.The results of experiment and simulation are used to reveal the deformation mechanism of colluvial landslide with step-like deformation in the Three Gorges Reservoir.

三峡库区具台阶状位移特征的堆积层滑坡是三峡水库运营过程中重要的灾害类型，对库区航运安全及滑坡影响区内的居民生命财产造成了严重威胁。通过典型滑坡工程地质调查，详细研究三峡库区具台阶状位移特征的堆积层古、老滑坡的地质环境特征，特别是滑坡坡体结构和滑面地质结构特征；分析滑坡动态监测信息，综合采用统计分析、力学分析、工程地质学分析等手段系统研究此类滑坡的运动学特征；利用环形剪切实验和扫描电镜实验研究滑带土在不同剪切条件下抗剪强度、孔隙水压力及其微观结构的变化规律，探讨堆积层滑坡台阶状变形条件下抗剪强度的衰减与再次增长规律；以八字门滑坡、塘角村1号滑坡为例，考虑滑面剪切强度大小空间分布的差异性,采用三维数值模拟方法分析滑坡在库水位与降雨耦合作用下渗流场、应力场与应变场的变化规律，研究库区具台阶状位移特征的堆积层古、老滑坡复活条件和变形演化规律，揭示三峡库区具台阶状位移特征的堆积层滑坡变形机理。

对三峡库区具台阶状位移特征的堆积层滑坡进行变形机理研究，具有重要的理论意义和实际价值。选择三峡库区具台阶状位移特征的堆积层滑坡塘角1号滑坡、花园养鸡场滑坡、新滩滑坡、八字门滑坡进行工程地质调查，详细分析具台阶状变形特征的堆积层滑坡地质条件，建立其地质模型。使用探井揭露塘角1号滑坡滑带，观察滑带特征并采取滑带土样品。研究结果表明：三峡库区具台阶状变形特征的堆积层滑坡是在长期的重力作用下，沿着土层与基岩面发生蠕滑变形形成，由于堆积层滑坡体积巨大，很多堆积层滑坡形成了双层滑动面。.对塘角1号滑坡和花园养鸡场滑坡进行了地裂缝和孔隙水压力的监测，并根据滑坡变形的差异性对塘角1号滑坡进行了危险性分区。通过对变形曲线、变形与影响因素、变形的空间差异性分析，研究了三峡库区具台阶状变形特征的堆积层滑坡时空变形演化规律。研究结果表明：堆积层滑坡表现出渐进式破坏，变形速率受降雨和库水位影响大，滑坡在卸荷带或水库变动带处易出现局部滑动。.在塘角1号滑坡滑带土常规试验测定滑带土基本物理参数的基础上，采用环形剪切试验研究滑带土在不同剪切条件下剪切强度的衰减与再次增长。采用扫描电镜、X-射线衍射方法，研究滑带土在不同浸水时间下矿物成分、结构构造的变化规律。研究结果表明：随剪切速率的增加滑带土残余抗剪强度逐渐降低，滑带土在短时间固结后并未出现明显的强度增长，可能与滑带土的粘粒含量低有重要关系。随着土样浸泡时间的增加，样品内溶蚀现象比较明显。.采用Geo-studio、Flac3D等软件对塘角1号滑坡、花园养鸡场滑坡进行了数值模拟，分析了降雨和库水联合作用下滑坡应力场、渗流场和位移场的变化规律。结果表明：库水位升降对堆积层滑坡前缘地下水位的影响很大；在库水位升降与降雨耦合作用下，剪应变增量、位移与塑性破坏区会增加，从而导致堆积层滑坡局部破坏。根据三峡库区堆积层滑坡具台阶状变形的特征，采用基于影响因子分析的灰色GM(1，1)-BP神经网络模型和警戒速度方法对滑坡进行了预测预报。总之，以上成果完善与发展了三峡库区具台阶状变形特征的堆积层滑坡变形机理研究。