Stability Analysis Of Rock Slope Based On Saturated And Unsaturated Seepage Theories

The seepage of the groundwater in the slope is closely related to the reservoir water level and rainfall.When the hydropower project is completed,slope stability of the reservoir will be affected by the fluctuation of the reservoir water level and rainfall infiltration.If it is not handled properly,these factors may lead to the occurrence of landslides and thus affect the operation of the hydropower station.At present,the study of the influence of the saturated and unsaturated theories on the soil slope stability is relatively mature compared with the rock slope.The first level hydropower station in Jinping is the highest arch dam in the word.The geological condition of the slope is complex.Rainfall in this area is frequent.The influence of reservoir water level and rainfall on the stability of the slope is remarkable.Taking the left-bank slope of Jinping hydropower station as an example,based on the saturated and-unsaturated seepage theories,the seepage is calculated under the changes of water level and rainfall.In addition,the factor of safety of the slope is worked out with the Voctor-Sum FoS Method during the seepage.New findings are as follows:(1)Combining vector and slope stability analysis method with finite element method,based on the real stress state of the slope,the safety factor and potential gliding direction of different water level and rainfall condition can be obtained easily during the numerical simulation.(2)Using saturated seepage theory to analyze the seepage of groundwater in the slope during the first reservoir impoundment,the change of the stability of the sliding failure mode of the left bank dam is analyzed during the storage process.The results of the study show that the safety factor increases with the rise of water level,and the safety factor is higher with the groundwater into account than that without considering the underground water.(3)the saturated seepage theory is used to study the stability evolution of the slope during the process of reducing the water level of the reservoir at different speeds.The results show that when the reservoir water level has a rate of 1m/d from the elevation1880 m to 800 m,the safety factor of dam on the left bank of the head slip failure mode is reduced from 1.214 to 1.147,and the safety factor approached a determined value as the water level tended to be stable.When the drawdown speed reached 2m/d,the safety factor decreased more quickly.(4)Based on the theory of unsaturated seepage,the seepage of groundwater in the slope under rainfall is analyzed,and the influence of different rainfall conditions on the slope stability is studied.Results shows that,due to the weak unloading zone below the bedrock with good integrity and low permeability,so the rain infiltration in the weak unloading zone firstly formed the transient saturated zone.With the expansion of transient saturated zone,its influence on the stability of the slope safety factor is more obvious with the increase of rainfall time.