| Since the completion of the Three Gorges Dam, the stability of the slope in the reservoir area, especially the old landslide, has become worse, which brings a serious threat to the residents and buildings in the landslide area. This is because of the seepage and stress field of the slope are changed by the water storage Bazibian landslide is located in ShuangLong village ten groups,Fulin district of Chongqing city, which is the upper reaches of the Three Gorges Reservoir area, from the Three Gorges Dam 472.5km, volume of about 150×104m3.The landslide is more developed in this region.Landslide accumulation body is easy to rise under the influence of internal and external factors.The houses on the back of the landslide have cracks under the influence of the early rainfall and the river.In recent years, after the large-scale artificial loading in the landslide area, the deformation of the accumulation body is obvious, and the stability of the landslide will be decreased with the increase of the rate of reservoir water descent. The revival of the old landslide will endanger the life and property safety of the people on the slope, and will break the traffic path and threaten the Yangtze River channel. So it is of great practical significance to study the mechanism and stability of the landslide,at the same time, the research on the reactivation and stability analysis of the old landslide in the Three Gorges Reservoir area under the comprehensive action of reservoir water, rainfall and large-scale pile load has certain theoretical reference value.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 FLAC3 D numerical simulation software to simulate the landslide under the factors such as rainfall, reservoir water, pile load and other factors, analysis of the old landslide revival mechanism.Sensitivity analysis of various factors affecting landslide stability by orthogonal test method.Using Geo-studio software to simulate the seepage field in the main deformation zone of the landslide, and the change of the seepage field under different conditions is obtained, and the stability evaluation and prediction are made. By means of the above methods, the main results are as follows(1)Bazibian landslide is formed by the accumulation of the gentle dip bedding slope of sand and mudstone after its failure,and deformation and failure model is "sliding and fracturing",the accumulation body of the landslide is in the middle thick and thin distribution on both sides.Thickness is generally about 14-20 m, the thickness of up to 22-23 m. The sliding loess bed is stratum of Shaximiao Formation(J2s), is a concave arc on the whole, the overall slope is generally about 10 degrees, the middle of a slightly flat about 5 degrees.(2)The earliest records of old landslide deformation periods of heavy rainfall in 1981,the main deformation is the wall cracks in the rear of the building.At the time of the first water storage of the reservoir in 2003,Local bank collapse deformation occurred in the front of the accumulation body.Nowadays, the deformation of slope is mainly occurred in the construction of artificial pile.Continuous development of shear cracks along the posterior boundary of the accumulation body, and the crack development characteristics of envelope like sutures.The deformation in the middle is mainly the wide cracks on the platform and the development of the fracture zone, subsidence zone on the right side retaining wall.In particular,the settlement of the retaining wall and the fracture zone with the platform ground fissures in the left side and the accumulation body settlement belt in the right side has the continuity characteristic.According to the characteristics of slope structure and deformation and fracture, the middle part of landslide is divided into strong deformation zone.Further analysis shows that the accumulation of body deformation mode for the reactivation of booster and landfill, rainfall, reservoir water is the main factor resulting in the accumulation of deformation.(3)Using the finite difference method of Flac3 D software to simulation analysis,the landslide has good stability under natural condition, the displacement and the principal stress is small, and the stress concentration is not found.With the gradual increase of rainfall, reservoir water, pile load and other factors,the increase of displacement is increasing and the principal stress value is increased,landslide, especially in the central accumulation body,appear strong stress concentration,the profile image shows the development of strain concentration zone along the top of the bedrock,the presence of shear slip along this surface may occur in the accumulation body(4)Using Seep module of Geo-studio software to simulate the seepage field,with the reservoir water level decreased, the landslide infiltration line continued to decrease,but in the process of reducing the lag effect, the existence of water head difference forms the dynamic water pressure, which is not conducive to the stability of the slope.Further research shows that the faster the reservoir water level is, the more serious the lag of the infiltration line is, the more obvious the head difference is,the greater the downward seepage force is, the greater the impact on the stability of the landslide.(5)Use of Morgenstern- Price limit equilibrium method to analyze the local and global stability of the deposit.After pile construction,landslide as a whole and strong deformation zone in respectively in the basically stable and unstable state;Increase the daily decline to 1.2m/d after the coupling calculation with the rainfall conditions,landslide as a whole and strong deformation zone in respectively in the basically stable and unstable state,The overall stability of the calculation results is greater than, but close to 1.05,the stability of the landslide reaches the critical value. |
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