Study on the characteristics of sliding zone soil and occurrence mechanism of Qiaojia Lanniqing landslide in Zhaotong
Sliding zone soil is the product of the landslide development process and provides a good record of the gestation-evolution of landslides.Taking Lanniqing landslide in Xiaohe Town,Qiaojia County,Zhaotong City as an example,by using the methods of field geological survey and tests,the physical and mechanical characteristics of Lanniqing landslide sliding zone was elaborated.At the same time,using XRD diffraction analysis to analyze the mineral composition of soil and SEM to observe the microstructure of soils,the characteristics of Lanniqing landslide sliding zone soil were described from different perspectives.On this basis,the formation,evolution process and driving mechanism of Lanniqing landslide were revealed.The results show that:Lanniqing landslide sliding zone soil is characterized by abundant clay minerals,high clay content and fine texture.It has distinct clay characteristics.In addition,it contains significantly more fine particles than the sliding bed soil,indicating that there were many shear dislocations in the sliding zone during the landslide preparation process.Fast shear tests on sliding zone soils at different moisture contents show that sliding zone soils have significant strain hardening properties.The shear strength gradually decreases as the moisture content increases.In particular,the sliding zone soil lose much of their strength at a moisture content of 40%and become very soft.The cohesion and angle of internal friction are high at low water contents and decrease with increasing water content.The test results show that under rainfall conditions the soils exhibit distinct soft clay characteristics as the water content increases.The widening of the Lanniqing Village road in the middle of the slope,the Y093 road at its rear edge,and the long-term effects of traffic loads all contributed to the gradual internal deformation of slope,which in turn produced the development of a potential sliding surface and multi-period creep deformation on this sliding surface.The soil in the slip zone becomes more textured and has a higher clay content as a result of repeated shear sliding.Furthermore,the low permeability sliding zone is more likely to create a water barrier during rainfall because of the characteristics of clayey soil materials.In addition,the strength of the soil is gradually decreasing and the soil is rapidly softening under the condition of rainfall.The hydrostatic pressure generated in the shear zone and the excess pore water pressure caused by the local water barrier of the sliding zone directly lead to the occurrence of the Lanniqing landslide.Therefore,the process of incubation and excitation of Lanniqing landslide can be divided into three stages based on its occurrence mechanism:the preliminary formation stage of the slip zone area,the slip zone development stage,and the formation stage of the stagnant water layer in the slip zone and the landslide.The research results can provide references for the systematic study of rainfall-type landslides in mountainous areas.
Lanniqing landslidesliding zone soilphysical mechanical propertyformation mechanismlandslide evolution process
NETL
NSTL
万方数据
维普
