| The Three Gorges Reservoir areas have complex natural and geological conditions with frequent occurrence of flood and rainstorm, so since ancient times the geological hazard of landslide develops in these areas. In 2003,as the reservoir began to store water,hydrodynamic environment of landslide in reservoir area was changed,inducing the whole or part deformation in some landslides. The bojishi landslide lies in the left bank of the Yangtze River of xuetang town,renyi village, Fuling district,Chongqing city, which away from the Three Gorges dam about 455.7km.The landslide develops in the bedding slope of sand-mudstone interbed, and the volume of the landslide is 1760000m3. Local deformation of the landslide was found several times in the flood season s ince 1950. A certain degree of deformation appeared in the middle-front part of the No.?landslide after the impoundment of the Three Gorges reservoir.With the level of daily decline increasing from 0.6m/d to 1.2m/d in the reservoir water,the physical and mechanical properties of rock-soils and the seepage field can be changed,which in turn affects the stability of the landslide. The deformation of the bojishi landslide endangers the safety of the residents' life and property on the slope. At the same time, once the whole or part of the landslide falls into the river, which will cause a certain threat to the roadway and the passing ships. Therefore, research on the bojishi landslide deformation mechanism and stability, with great practical significance, and it also has certain reference value for the study on the stability of the same type of landslide in reservoir.In this paper, the basic geological conditions and the structure characteristics of the slope are identified,and the deformation and failure features of the landslide are investigated and analyzed in detail.O n this basis,the recent deformation mechanism and the influencing factors of deformation of the landslide were analyzed. FLAC3 D numerical simulation software was used to simulate the deformation and failure characteristics of the No.?and No.?, and the simulation results with the actual survey results were compared. Finally, through the analysis of the deformation influence factors and deformation characteristics of landslide,qualitative judgment on the stability of No.?and No.?landslide was made.Limit equilibrium method was used to calculate the stability of No. ? landslide in natural and heavy rain conditions;the Seep/W module of GeoStudio software was used to simulate the seepage field of the No. ? landslide under the coupling action of water and rainfall,and then to analyze the stability and the development trends of the landslide under the action of reservoir water, rainstorm,and the increase in daily decline of reservoir water. Mainly obtains the following understanding and the achievement:(1)The bojishi landslide develops in the bedding slope of sand- mudstone interbed,and the formation mechanism is sliding- fracturing.It is divided into two zones.No.?slope formed earlier than No.?, a relatively small scale but larger later reformation.The formation time of No. ? landslide was relatively late, and the integrity of the landslide is relatively good.(2)No.?landslide existing deformation mainly found from the leading edge to 192 m. cracking in houses, settlement and cracking in garden,are mainly saw in 192 m,The width of deformation crack is mostly between 0.1~0.5cm;the length is generally 15~20m.the sign of deformation seldom found.a number of bank collapse develops along the 175 m,varied in form,the height of which generally is 1-1.5m.No. ?landslide deformation mainly found from 194 m to 206 m. cracking in houses, settlement and cracking in yuanba,are mainly saw in this zoom,The width of deformation crack is generally between 0.1~0.5cm,and the widest of them is about 3.0cm;the length is generally 5-10 m.The No.?landslide deformation is mainly affected by rainfall and reservoir water. the No.?landslide slip surface lies in above 175,so its deformation has nothing to do with the reservoir water, mainly due to heavy rains.(3)Soil structure of bojishi landslide is loose,under the condition of heavy rain, after rain water permeates into the bottom of the debris slope, due to the base cover interface distribution layer thickness is small but high purity of clay layer, which is relatively impermeable,so rain water only gathers and migrates a long the base cover, softening the rock and soil on the contact surface, reducing the shear strength, which is not conducive to the stability of landslide. The fluctuation of reservoir water level affects the No?. Bojishi landslide mainly in the following three points:(1)Because of the change of the water level in the front of the slope, the leading edge of the sliding can occur obviously hydrodynamic pressures, which is not conducive to the stability of the leading edge.(2) Reservoir bank reconstruction leads to the development of the leading edge collapse,part of the front edge of landslide disintegrating,which reduce the support of leading edge.(3)In the long term, the leading edge of the slop is soaked in the wa ter for a long time, which reduces the mechanical properties of the leading edge.(4)Flac3D finite difference method was used to simulate and analyse the deformation mechanism of landslide under the condition of rainwater?natural state and reservoir water. Through the analysis of numerical simulation results,we can infer that:(1)In the natural state, there is no obvious deformation in the other parts except for the small deformation in the No?landslide.(2)Under heavy rain, the landslide deformation is more co ncentrated;the maximum deformation is 30 mm, which is close to the deformation characteristics and deformation degree in reality.(3)Under the action of reservoir water, the maximum deformation is 34 mm in the middle of No?landslide, which is basically consiste nt with the actual deformation and failure characteristics.(5)The Seep/W module is used to simulate the seepage field under the action of reservoir water and rainfall. The results show that along with the change of reservoir water level, the infiltration line of landslide front is obviously lagging behind. In the simulation of rainfall,on the first day, most of the rainfall along the surface runoff and discharge, and only a small part of the infiltration of rain water on the surface of the slope formed a short saturated zone. In second days and third days, with the continuous infiltration of rain water, wetting front continues to push down in the slope, and the upper saturated area is enlarged.(6)Through qualitative analysis and quantitative calculation of stability,it is considered that: No. ? landslide is currently in an overall stable state, the front deformation zone is in a basically stable state.Under the fluctuation of reservoir water, the whole is in a basically stable state, and the deformation zone is in a unstable state. Under the natural condition, No.?landslide in an overall stable state;but in the rainstorm condition, the whole is in a basically stable state, and the local is in a unstable state. |
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