| ABSTRACTMajiaheba isolated rock mass has distinctive geological background and structure of rock mass, whose potential deformation and stability are important to Xiluodu hydroelectric station. On the basis of in-situ investigation, we carefully studied it and draw some conclusions.First of all, Maj iaheba fault was formed which was the result of the NW-SE directional shove press. Under the condition, rock strata began to distort and fold so that the NE directional Naligou anticline, Maanshan-Mimishan syncline and Shibantan anticline were formed. With the NW directional continually acted, Naligou anticline became more and more asymmetric, whose steep dip SE facet's shearing stress much accumulated and formed a group conjugated joint plane. When it continued to accumulate and was equal to or superpass the rock mass's shearing strength, it began to overthrust and shearing destruction so that Majiaheba fault was formed. With the development of progressive deformation, Majiaheba fault continually subducted and sheared and extended from NW to SE direction. When it extended to Shibantan-Majiaheba, it began to strongly obducted and climbed because of Shibantan anticline's resistance, and its easy movement developed to leading edge's compressed overthrust imbricated fault zone. As a result, it formed a thrust-nappe tectonics, whose root zone sheared and obducted, whose middle zone subducted and dilated, whose front zone strongly obducted.Second, by analyzing Jinshajiang wadi's rock mass stress field development and the development of finite element numerical modeling in the future, it shows us the following signals.With the increase of wadi's down-cutting depth, the range of displacement of stress extended and wadi's accumulation of stress's strength increased. Wadi's rock mass stress filed's development was divided into two stages: the first stage was the wadi down-cutting the 440m altitude, that is, the fault lied. During the stage the range of being affected was the upper rock mass. With the wadi down-cutting, rock mass's displacement of stress became wide and the whole wadi rock mass lied in the stage of load off and stress relaxation regulation. The second stage was the wadi down-cutting from 440m to 360m altitude which is today's bottom. During the stage rock mass's rate of the displacement of stress became slower. The whole wadi rock mass lied in slow regulation stage except that the wadi's rock mass stress accumulation quickly increased. By analyzing the result of two hundred years rheological finite element numerical modeling, bank slope rock mass stress gradient increased, especially, the rock mass of high-slope above the highway, fault zone and wadi in the left bank and so on. With the time passing away, the principal stress and shear stress's values and directions are no longer apparent variation. They show that rock mass stress-deformation lie in a slow regulation stage in the future.Third ,the results of linear elastic and rheological finite element numerical modeling showthat Majiaheba isolated rock mass抯 displacement of stress is mainly controlled by the geological conformation. The maximum principal stress and maximum shear stress trajectory both divert near the fault and among the rock mass which is surrounded by the fault and form some range of displacement of stress; there is a high stress zone at the bottom of the fault. On the contrary, there is a lower one in the fault zone. the principal stress and shear stress抯 values are negative in the place where the F1, F2 fault and F3 fault抯 conjunction and F3 fault抯 leading edge near the ground, which show that the special places lie in tensile stress and slow relaxation condition.Fourth, under all the condition, as a whole, Majiaheba isolated rock mass has high margin of safety and lies in a stable condition. Under the aggregate preparation ground condition, the high margin of safety not decrease but increase because it distributes resisting force more than the sliding force. Under the dangerous condition(stora...
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