Influnence Of Rise And Fall Of Donghe River Water Table On Stability Of Guangmang Landslide

After the impoundment of the Three Gorges Reservoir area, a tributary of Donghe river affected by high water table in reservoir lead to produce new geological disasters of reservoir bank, and it affected the residents’ lives and property safety. Guangmang landslide locates on the right bank of Donghe river, Therefore, the study of the changes of the stability of guangmang landslide affected by river water table rise and fall has a great significance.This paper investigated the engineering geology and hydrogeology conditions of guangmang landslide area, analyzed the formation process and mechanism of the landslide,by the qualitative analysis and quantitative calculation methods, achieved the groundwater distribution characteristics of landslide area in the different time and different working conditions, used the landslide stability calculation method to calculate the stability of the landslide when the river water table rises and falls in different time and different working conditions, and summarized and analyzed the change rules of stability of the landslide. The main research results are as follows:1. The landslide is a small soil traction landslide, the landslide is steep, landslide material are silty clay and the stone of fragments in Quaternary, it is slightly loose-dense, poor stability and below of it is the mudstone of Jurassic Shaximiao. Landslide groundwater recharges from rainfall and Donghe river, in the Three Gorges Reservoir operations, the change of the Donghe river water table has a greate impact on the stability of the landslide. The analysis of the engineering geological conditions of the landslide area shows that the landslide area unfavorable topography and geotechnical characteristics of the formation are internal factors, and the changes in elevating the hydrogeological conditions of the landslide area by the Donghe river water table is the predisposing factors landslide slip deformation.2. Donghe river water table rise and fall have a greater impact on the groundwater flow field of guangmang landslide. When the Donghe water table rises, changes of the guangmang landslide seepage are as follows: landslide body water table rises with the river water table rise; affected by the nature of landslide itself, the single saturation line was a certain slope of the curve, and close to the airport surface the slope is greater, with the rise of water table, the change of slope of saturation line at different times is small, the difference of the water table between the slope and the river is small. When the Donghe river water table falls, changes of the guangmang landslide seepage are as follows: landslide body water table drops with the river water table fall; affected by the nature of landslide itself, the single saturation line was a certain slope of the curve, and close to the airport surface the slope is greater, with the fall of water table, the change of slope of saturation line at different times is small, the difference of the water table between the slope and the river is small.3. The impacts on the landslide stability affected by the rise of Donghe river water table are as follows:when the Donghe river table rises, the rise of the water table of guangmang landslide lags behind the rise of the river water table, the stability of the landslide falls, and then rises, and the changes of the stability is small. When the water table drops to 169 m, the stability coefficient reaches a minimum, the landslide stability is the worst.The river table rise overall has little effect on the stability of the landslide, the faster the water table rise, the landslide stability slightly reduced.4. The impacts on the landslide stability affected by the fall of Donghe river water table are as follows:When Donghe river water table falled, the fall of water table of the guangmang landslide laged behind the fall of river water table, the stability of the landslide gradually decreased, and the changes of the stability is large. Before river table decline at 171 m, landslide stability decreased rapidly, after that the rate of decline of landslide stability is relatively moderate, the rise of river table has a great effect on the stability of the landslide.