堆积层滑坡台阶状变形下滑带土抗剪强度衰减与再生规律研究

Colluvial landslides are common geological hazards in the Three Gorges Reservoir. The deformation process of colluvial landslide is not only affected by the combined effects of the rainfall and water, but also influenced by shear strength of sliding soil. The Bazimen landslide and Tangjiaocunyihao landslide in the Three Gorges Reservoir are taken as typical examples of colluvial landslides. Deformation characteristics of colluvial landslide and structure features of sliding zone are studied through engineering geology investigation and trenching, in order to investigate the relationships between landslide surface deformation and defomation of the sliding zone. Based on the deformation characteristics of colluvial landslides, the ring shear experiment are used to study the rules of strength decay and recovery of sliding soil under landslide deformaion and landslide static by changing the condition of effective normal stresses,shear rate, shear mode and rest period. The results aim to explore the variation law of shear strength of sliding soil under the condition of landslide step-like deformation. The micro-mechanism of shear strength recovery is discussed by the scanning electronic microscope experiment.On the basis of geology model of typical colluvial landslides,the numerical simulation method is adopted to simulate the evolution of landslide step-like deformation process 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 research results are used to develop the strength theory of sliding soil, reveal the deformation process of colluvial landslide and make emergency plan in the Three Gorges Reservoir.

堆积层滑坡是三峡库区常见的地质灾害，其变形演化不仅受降雨、库水位作用引起的孔隙水压力变化影响，而且也与滑带土抗剪强度的变化关系密切。本项目以塘角1号滑坡和八字门滑坡为例，通过滑坡现场调查和槽探工作，研究典型堆积层滑坡变形破坏特征和滑动带发育特征，揭示堆积层滑坡地表变形与滑动带变形的内在关系。根据堆积层滑坡台阶状变形特征，通过环形剪切试验改变有效法向应力、剪切速率、剪切模式、剪切静止时间模拟研究滑坡大变形和静止时滑带土抗剪强度的衰减与再生规律，揭示堆积层滑坡台阶状变形下滑带土抗剪强度的变化规律；并采用扫描电镜技术探讨滑带土强度再生的微观机制。在滑坡地质模型建立的基础上，考虑滑动带强度取值的空间差异性，采用三维数值模拟技术研究堆积层滑坡在降雨、库水位耦合作用下台阶状变形演化规律。研究成果对发展滑带土强度理论、探究堆积层滑坡变形演化规律和制定三峡库区堆积层滑坡防灾减灾预案具有重要的科学意义。

本项目对堆积层滑坡在台阶状变形下滑带土的强度衰减与恢复进行了研究，通过对塘角1号滑坡、八字门滑坡的现场调查和槽探工作，发现典型堆积层滑坡的变形与滑带土强度、外界因素（库水位和降雨）和局部地貌关系密切，变形的差异性受局部地形影响；通过对滑体条块的受力分析，建立滑坡变形与滑带土强度的函数关系；在对两个滑坡滑带土进行常规物理分析的基础上，采用环形剪切试验对粉砂和粉质粘土两种不同类型的滑带土进行不同剪切形式的测试，得出以下结论：1）粉砂类滑带土受前期固结压力的影响较小,且与剪切速率呈现负相关；2）不同类型的滑带土在短时间受加速剪切或减速剪切时，滑带土强度改变的趋势都试图阻碍速度的进一步改变，维持原有的运动状态；3）无论粗粒土还是细粒土，都在短时间的静止后，呈现明显的强度恢复现象，强度恢复率与时间呈现指数关系。基于滑坡现场监测资料，采用三维数值模拟方法揭示了堆积层滑坡渗流场在降雨、库水位升降条件下的变化规律，并对滑坡的应变场进行了模拟研究。现指数关系。基于滑坡现场监测资料，采用三维数值模拟方法揭示了堆积层滑坡渗流场在降雨、库水位升降条件下的变化规律，并对滑坡的应变场进行了模拟研究。