Dynamic Stability Analysis Of Landslide Combined Effects Of Heavy Rain And Water Level

The water level of impounded dam has been changing between175m-145m afterthe completion of the Three Gorges reservoir and the average annual rainfall here isabove1000mm.However, the environmental factors such as changes in water level andheavy rains may easily lead to geological disasters including landslides. Reservoirlandslides have been regarded as the focus of the study by experts and scholars athome and abroad. After the study of a large number of domestic and foreign literatures,the author made the simulation and analysis about the garden chicken factorycombined with the geological conditions of the study area, the water level of the ThreeGorges reservoir scheduling situation and local rainfall data.This dissertation describes the recent research results of scholars about stabilityanalysis of reservoir landslides and saturated-unsaturated seepage of slopes. Bydeformation data for analysis of typical landslide in Three Gorges Reservoir, it isconcluded that the changes in water level and rainfall are the main factors affecting thestability of the landslides. Seepage analysis is the basis of stability analysis. Accordingto the Three Gorges reservoir scheduling situation and local rainfall data, the author setup six kinds of simulated conditions including drawdown rate of three differentconditions, two different water level rise rate conditions and a decline water levelcondition with rainfall to simulate as simulative working conditions. At the meanwhile,the actual working conditions have been made in full accordance with the actualchanges of water level and rainfall in study area. The saturated-unsaturated seepagesimulations were executed about landslides in the study area using GEOSTUDIOsoftware SEEP/W module. Then the simulation results were made use of leading intothe stability analysis by SLOPE/W module. The following conclusions were made:1.The decline in water level is the main factor leading to drop of the stability oflandslides, and the safety factor of landslides may first decrease then increase with thedecline in water level. The reason is that when the water level began to fall the porewater pressure is difficult to disappear immediately and the penetration is much greater than the buoyancy, resulting in the decrease of safety factor. After a period ofdecline in water level due to better penetration slope, slope inside the hydraulicgradient is relatively smaller leading to the decrease of penetration and dominance ofbuoyancy, the safety factor of landslide will gradually increase.2. After researchingthe simulation results in three different simulative working conditions of distinctdrawdown rates, it is concluded that the faster the water level drops, the lower theminimum safety factor of landslide is.3. Persistent heavy rain will greatly reduce thesafety factor of the landslides, and heavy rain is the significant negative effect oflandslide stability negative. The safety factor of landslide in rainfall conditions hasreduced by up to1.56%under otherwise identical conditions.4. The rise of water levelmay enhance the stability of landslides. According to the simulation results in twodifferent rising rates of water level, the safety factor of landslides may ascend fasterwhile the water level is rising faster.5. The simulation results in actual workingconditions are similar with that in simulative working conditions. In addition, thepersistent decline of water level has a greater impact on the stability of landslides thanthe short-term large fluctuations in water level. The rain factor is more important inactual conditions, and the most dangerous situation often occurs during the rainyseason.