| The Three Gorges Reservoir area is a landslide prone area, after the impoundment of the reservoir, the reservoir hydrological and geological conditions occur great change, Some old landslides have occurred deformation under the condition of 0.6m/d reduction velocity, with a descending speed increased to 1.2m/d may cause more landslides deformation, thus threatening people's lives and property safety and Yangtze River shipping safety.Hujiatuo landslide located in Hongyan village 4 group, Tiger Town Fengdu county Chongqing city, in the left bank of the Yangtze River. It is 437 km from the Three Gorges Dam. Landslide area of 9.98×104 m2, volume of 230 ×104 m3. Before the reservoir storage, local deformation occurs under the influence of rainstorm, formation two deformation zone. After reservoir water storage, affected by reservoir water, the deformation of the strong deformation zone is increased, in the case of increasing the speed of falling, there is likely to be unstable. Once the instability, will have a back type damage, deterioration stability of the weak deformation, increasing its deformation, and even caused the whole landslide revival, threaten the area of Yu Feng road and along the road on both sides of 23 residents. Thus, selection of HuJiaTuo landslide as the research object, to study the mechanism and stability of the resurrection.Based on the collection of relevant geological data and survey data of the study area. Also carried out a field survey of landslide. The characteristics of the revival and deformation of the landslide at the present stage are analyzed comprehensively. The formation mechanism of the old landslide is analyzed. Based on the combination of geological analysis and numerical calculation, the revival mechanism of the landslide in the rain and reservoir water was studied. Finally, qualitative and quantitative methods are used to evaluate the global and local stability of the landslide. Specific research results are as follows:(1) According to field research, combined with survey data. The formation mechanism of landslide is analyzed.The old landslide occurred in the strata of sandstone and mudstone in the Jurassic Shaxi. The model of landslide deformation is bedding creep, along the soft mudstone layer. The old landslide deformation and failure mode is "creep crack". Landslide accumulation body is mainly composed of crushed stone soil.(2) According to the present situation of landslide deformation, the characteristics of the revival of the landslide are studied. After the occurrence of the landslide, landslide accumulation revival in 1982 under the impact of heavy rain. Landslide deformation has obvious zoning characteristics, according to the degree of landslide deformation, the landslide is divided into strong deformation area and weak deformation area. After the water storage of the Three Gorges Dam, the deformation of the strong deformation zone is further intensified under the action of heavy rainfall and reservoir water.(3) FLAC3 D finite difference method is used to simulate and analyze the variation characteristics of stress field and displacement field of landslide under the combined action of natural, rainstorm, rainstorm and reservoir water. The calculation results show that in the case of heavy rain, the landslide deformation intensifies, and has the characteristics of zoning. The simulation results are consistent with the characteristic of the landslide revival zoning. Under the combination of rainfall and rainstorm, the landslide deformation increases, and the deformation zone is developed to the rear part of the landslide. The simulation results are in agreement with the deformation characteristics of the landslide under the present condition of the landslide.(4) Two dimensional seepage field calculation model of landslide is established, based on the principle of unsaturated soil seepage. The characteristics of landslide infiltration line and pore water pressure change at different time of landslide under the action of rainfall and reservoir water. The seepage calculation results are introduced into the stability of the landslide. The stability of the landslide is calculated by Morgenstern-Price method, and the calculation results are analyzed. Under the condition of the current situation: Under the condition of reservoir water 0.6m/d drop velocity superposition rainfall. the stability coefficient of the landslide strong deformation zone is 1.020, the stability coefficient of the weak deformation zone is 1.035, the overall stability coefficient of the landslide is 1.074. Under the condition of the current situation, landslide stability coefficient decreases gradually from the front to the back, the landslide deformation performance for the backward failure. Under the condition of increasing the descending velocity: Under the condition of reservoir water 1.2.m/d drop velocity superposition rainfall. the stability coefficient of the strong deformation zone of the landslide is 1.006, the stability coefficient of the weak deformation zone is 1.021, and the overall stability coefficient of the landslide is 1.069. The stability of the strong deformation zone is further reduced in the case of increasing the velocity of the falling velocity.(5) The random time-varying reliability model of landslide is established, and the failure probability of the whole landslide and the local landslide at different conditions are analyzed by the Monte-Carlo simulation method. The calculation results and the limit equilibrium method are corresponding. The stability of the strong deformation zone is the worst, and the probability of failure is maximum... |
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