中文摘要：

古水水电站争岗大型滑坡堆积体方量高达4．75×10^7m^3，地质勘测揭示该滑体主要由基岩、滑带土和松散堆积物组成，且滑带土层为贯通的底滑面；首先对堆积体历史演化过程和滑坡体形成机制进行详细分析，对现状及未来失稳模式进行定性判别，认为滑体处于沿贯通底滑面蠕滑变形状态；对滑带土基本特性分析的基础上，开展不同条件下室内大型直剪试验，研究天然状态下变形和强度的关系、抗剪性能参数取值；探讨含石量、含水量对抗翦强度的影响；从而寻找出合理的计算参数，开展稳定性评价。研究结果显示：天然状态下，滑带土黏聚力为30．31～43．94kPa，内摩擦角为25．82°～30．49°；且含石量和含水量对抗剪强度影响显著，含石量75％为阈值，低于此值，抗剪强度随含石量的增加而增大，超过此值，随含石量的增加而减小；含水量的增加导致强度降低，黏聚力、内摩擦角降低基本呈指数关系。稳定性评价成果与定性分析相吻合，滑体各种工况下均存在滑塌的可能性，开展治理措施研究显得至关重要。

英文摘要：

The volume of Zhenggang large landslide accumulation body in Gushui hydropower station is up to 4.75× 10^7 m^3. Geological investigation shows that the landslide is mainly composed of bedrock, slip zone soil and unconsolidated accumulation, and that the slip zone soil layer is the transfixion slipping surface. Firstly, the history evolution process of the accumulation body and the formation mechanism of the landslide were analyzed in detail. Qualitative discrimination was made on the current situation and the future instability mode. The landslide is in the state of creep deformation along the transfixion slipping surface. Based on the analysis of basic characteristics of slip zone soil, the large-scale direct shear tests on slip zone soils in laboratory were carried out under different conditions. Not only the relations of deformation and strength and the values of shear parameters in natural state were studied respectively, but also the effects of stone and water content on shear strength were analyzed. The reasonable calculation parameters were found, and the stability analysis was conducted. The analysis results show that the values of cohesion and internal friction angle range from 30.31 to 43.94 kPa and 25.82° to 30.49° , respectively. The contents of stone and water have significant influences on shear strength. The threshold value for stone content is 75%, increasing the stone content which is less than 75% causes the increase of shear s~ength; However, the shear strength decreases when stone content is higher than 75%. The shear strength and values of parameters decrease with the increasing water content, with which the relations are approximate to exponential function. The stability results are consistent with the qualitative analysis, and the landslide is possibly slumped under any condition. Therefore, it is very important to choose the best economic and reasonable treatment and evaluation.