Research On Revival Mechanism And Stability Of Lijiawan Landslide In The Three Gorges Reservoir

The Lijiawan landslide is located in Taohua stream along the right bank Slope on three hole village FengCheng town Chongqing Changshou district, where therainfallis plentiful and large, the influence of water level fluctuation and rainfall, the deformation in the study area has the tendency of further development, considering distribution of a large number of houses in the research zone, residents and enterprise employees 368 people, and water supply pipelines through here,which has the daily water consumption task for the residents of the Changshou area more than fifty thousand households. if the landslide instability will threaten the life property safety of the residents and enterprise employees, so the resurrection mechanismof the old landslide and to evaluate its stability has important practical significance.This article through to geological structure, hydrogeological characteristics of landslides, development characteristics of strong to weak deformation area is analyzed, revealing the resurrection mechanismof the old landslide and influencing factors; Using Geo-studio software to simulateits stabilityin main deformation zone of landslideunder different working conditions, through analysis of the change of the saturation line, the difference of pore water pressure isoline map, evaluate its effect on the stability of the landslide.On this basis, researching different shear strength index, and the size of the rainfall and water level elevation by using grey correlation theory is sensitive to the stability of the landslide intensity. Finally, the FLAC3 D numerical simulation of the stress and strain field and plastic zone on the main deformation areaare studied, the following main achievements.(1)The Lijiawan landslide is the result of joint action of internal cause and external cause, the internal factor are the landform, geological structure, and the structural characteristics, the external cause are mainly the rainfall and river incised. Due to the sandstone and mudstone structural characteristics of hard and soft, the slope is easy to induced the pressing crack to the precipitous direction along the gentle layer. Under the condition of the heavy rain, the Slope push in the combined effect of the hydrostatic pressure and the pore water pressure.(2)The resurrection of the Lijiawan landslide is divided into three strong deformation zone, one weak deformation zone.The resurrection of the Lijiawan landslide caused by the change of water level and rainfall, rainfall is the main inducing factors, mainly displays in: the influence of rain infiltration reduce the shear strength of soil, increase the weight of Slope, thus increasing the Slope sliding force. From the unsaturated soil mechanics principle, rainwater infiltration can make the matrix suction of landslide body decrease, the effective stress reduce, at the same time, soften the sliding-zone soil, led to the decrease of the cohesive force in the clay minerals hydration, and transform the physical propertiesp of the Slope.(3)Using the Seep module of Geo-studio software to simulate the Seep age field in the front of landslide on the water level drop, the water level drops after a period of time, the soil infiltration line obviously lag behind the falling rate of water level, the Seepage line above the water. However, the upper Slope and landslide away from the water level, basically is not affected by the influence of reservoir water level, the faster the decline rate, the higher the SEEPage line, the greater the head difference, the greater the resulting Slope to the penetration, the greater the threat to the stability of the landslide.(4)Reservoir level decline rate of 0.6 m/d, 1.2 m/d in the process of declining, the Lijiawan landslide is in a state of stability to basic stability; and when decline rate of 0.6 m/d, 1.2 m/d, 3 d rainstorm(85mm/d), the Lijiawan landslide in the stable to unstable state.(5)Through numerical simulation analysis of the FLAC3 D software on the stress, strain and shear plastic zone the landslide stability of the four conditions was found that under the condition one, in the process of water decline, the front of the landslide partly occur the tensile stress concentration belt, landslide displacement changes only occur near the leading edge, the shear strain increment is concentrated in the geotechnical boundary surface, the deformation and failure of the landslide mainly along the main sliding surfaces; Under the condition three and four, the front tension stress distribution range is increased, the back of the landslide locally have the tensile stress distribution, plastic zone in the surface shear extension, and to the deep development.(6)By analyzing the effec of the three periods of the control project, according to the relevant provisions of “the technical requirements of three periods of geological disaster prevention engineering in the Three Gorges Reservoir region”, the suggestions about reinforcing measures of treatment engineering are put forward, in the preceding elevation one hundred and seventy-seven meters setting a row of twenty-six root of anti-slide pile engineering, on the left side elevation two hundred meters setting a row of seventeen root of anti-slide pile engineering, the back elevation two hundred and fifty-seven meters setting drainage engineering.