Influence of Water Level Rise on the Bank of Reservoir on Slope Stability: A Case Study of Dagangshan Hydropower Project

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This paper considers stability of slope under varying water level for the right bank of reservoir of Dagangshan hydropower project. SEEP/W and SLOPE/W are used for numerical analysis. Morgenstern-Price method is used for stability analysis. Change in Factor of Safety with the rise in water level is obtained. Three cases of water level rise are studied as fast, medium and slow. It is found out that, when water level rises, the water table also rises correspondingly hence changing the properties of the rock mass in slope and its behavior to different situations and stresses. With the change in the water table line, the property like permeability changes, which is a significant property for slope stability and affects directly the strength of rock mass. Also due to change in water table within the slope, the situation of saturated and unsaturated portions in the slope also changes which is a complex phenomenon to deal with. So it has to be considered as an important factor. The changing pattern of the factor of safety with the elevation is similar for the cases of slow and medium but it is different for fast case. There is difference in factor of safety for the same elevation for different cases so the speed of the rise in water level also influences the impact on the stability. The comparison of fast and medium cases show that the difference in factor of safety is low but while comparing the cases- slow and fast the difference is high.