Geological evolution analysis and numerical simulation of Qujiawan landslide group in Dongping reservoir

Based on the analyses of regional geological structure and the geological structure of Qujiawan landslide group in Dongping reservoir area, taking stratigraphical occurrence, hydrometeorological factors into account, it was hard to form large-scale rock landslides during the evolution processes. But speculating with the incised direction of the river valley, large-scale collapse of bedrock of the right bank may be induced by 3 times of tectonic movement which forms the three terraces of left bank of Zhongjian River because of intense structural role. According to the characteristics of collapse deposits and the river width, it is possible that large-scale collapse deposits are moved to the left bank of the river, covering upon the terraces, which is supported by photos from field investigation and analysis of mechanical parameters from bedrock. Five important stages during the evolution processes are selected and analyzed combining engineering geology and geological methods, considering that the landslides are on the axial part of Zhongjian River anticline, the characteristics of river valley incising along weak tectonic rock zone in geomorphology and the trail results of the parameters of geotechnical experiment, in order to determine section shape of the slope in each stage and draw geologic profile. Then geomechanical model is established by using FLAC3D; and a dynamic numerical simulation for the 5 important stages is carried out. From the calculation result, the speculation that collapse deposits from the right bank can pack on the left bank has been confirmed. Meanwhile, it is well explained that the deposits on left bank are much thicker than that on right bank; and there is an obvious difference in surface elevation between the two banks.