Formation Mechanism Study And Stability Evaluation Of The Complex Geology In New Main Site Of Fengjie County

Choicing new site for Fengjie county since 1984. Caotang area had been selected and planned in 1991, which is located at 5 km downstream of the Fengjie old city. Considering of Geological complexity and big risk, changing the site for the first time to Baotaping area which is located at east of the old city. Later, because of Baotaping slope is"falling nappe", changing the site for the second time to Sanma Mountain area in 1996, which is 13 km eight built-up areas and formed"a center, eight fundamental points"new city overall pattern. Currently, the main city building has been completed, which is located in a huge complex geology. At present, there are still considerable disagreement in the complex geology's formation mechanism and spatial strcture characteristic. As a result, site stability and catastrophe risk has plagued the city construction, economic development and livelihood security, which has become involved in national economic development and people's lives and safety of the urgent need to solve major environmental science issues in this region.Present paper has taken the new site main city of Fengjie County complex geology as study object and has expounded the complex geology's strcture character- ristic, boundary control conditions and the origin mechanism, which is based on collecting and collating analyzed area geological data, earlier period investigation material, predecessor research results.And through participates in the supplement investigation drilling and the geological survey work. On the basis of a reasonable geological- mechanical model, using two-dimensional finite element numerical simulation method, the first of the major conditions of the reservoir water level during the water saturation line for the rock mechanics numerical simulation. And then further use of two- dimensional finite element analysis and limit equilibrium calculation, the main city of sophisticated geological storage in the Three Gorges reservoir area and under the influence of human activities stress - strain characteristics of the whole, local stability. Papers main achievements are as follows:(1) Nearby the new site of Fengjie city, the regional geology structure's formation and development are controlled by nearly north and south profiling stress field. The three-dimensional crustal stress condition had transformed from"latent walk by the initial period slide"into"latent counter break"during the main structure formative year. Does not exist crustal stress environment to form tensional fault structure.(2) The main city's complex geology a large old landslide - Sanmashan landslide, its genetic mechanism is "the lower part of the shear creep - the upper part of rip - Central cut "type landslide which was controlled by the lower low-angle soft rock of Sanmashan Mountain. Landslide Sunjiagou bounded to the east, the west side of the front of the Po Yang Ping ditch as the boundary, in the back of the package groove to the deaf community, after the north edge of the steep hill is bounded by Sanmashan Mountain, south of the Yangtze. Resurrection of the body produces accumulation of the local secondary sliding front, the formation of the Laofangzi landslide, Zhiwuyouchang landslide and Houzishi landslide and so on- three small slump body.(3) Sanmashan landslide's seepage numerical simulations show that the natural condition with little change in rainfall seepage field conditions, rain has little effect on the seepage field. Reservoir water levels of the Sanmashan landslide's seepage and stability have a greater impact.(4) Sanmashan landslide's stress and strain concentration zone are mainly distributed in the main slip zone, the secondary slip zone and banks nearby, the edge of the local landslide occurred weak tensile stress state, the deformation of the secondary landslide is bigger than the main landslide. Secondary landslide's stress and strain increases with the increase in reservoir water level, water level had no effect on the corresponding field should be variable slightly decreasing trend. Decline relative to the reservoir water level, water level rise on the slope stability is particularly bad.(5) According to the calculation of limit equilibrium analysis, Sanmashan landslide in the Three Gorges reservoir water level changes in the overall process is stable. Front of local deformation of rock in the reservoir water storage and long-term effect of heavy rainfall, there is the possibility of damage occurring.