Study On Slope Stability Of Hydropower Stations Influenced By Fluctuation Of Reservoir Water Level

Most hydropower stations have long service lives.The life cycle of hydropower projectsconsists of four stages,design,construction,operation and retirement.In the four stages,the fluctuation of reservoir water level is considered to be one of the key factors that cause the landslide of reservoir bank slope.The impact of large-sized slides on the reservoir area and downstream is often catastrophic.Studies on the mechanism of slope instability caused by water level fluctuation and Relevant numerical simulation work can provide scientific reference and guidance for landslide control.Therefore,this paper takes the left bank of step one hydro-junction in Jinping as an example,uses the ANSYS software to automatically divide the discrete mesh function,and carries out full-scale three-dimensional numerical modeling of the slope geometrical and geological model.The model is imported into FLAC3 D software,we use FLAC3D's Fish script language to establish the seepage constitutive criterion.In the extreme case such as the rapid fluctuation of reservoir water level,the influence of reservoir water level fluctuation on slope stability is studied from the point of view of effective stress.The safety evaluation mechanism of bank slope is discussed,and the research results can provide theoretical guidance and suggestions for slope drainage and reservoir water regulation.In this paper,the influence of water level fluctuation on bank slope is studied from two aspects:1.the "hysteresis effect" of the change of the groundwater level after the rapid rise and fall of the reservoir water level.Results indicate that,(1)The safety factor of the slope decreases gradually in the process when the reservoir water level ceases to rise and the groundwater level gradually reached the seepage equilibrium state;The safety factor of the slope increases gradually when the reservoir water level stop falling and the groundwater level gradually reached the seepage equilibrium state.(2)Compared with the other two stages,the safety factor of the slope is the lowest when the water level is declining rapidly.When the water level drops to 1640 meters,the safety factor of the slope is less than 1.3.In this case,the slope is easy to be disturbed by other disturbances such as earthquakes.(3)By improving the drainage condition of the slope,we can eliminate the "hysteresis effect" of groundwater level changes;And we can also eliminate its adverse effects on slope stability by regulating the drawdown rate of the reservoir water level.2.the weakening effect of the water on the slope rock mass,include the weakening effect of water on the weak structure of the fault and the weakening effect of the reservoir water fluctuation on the rock mass in the "Water-Level-Fluctuating Zone" of the slope.The results are summarized as follows.(1)The softening of f5 and f8 faults has little effect on the stability of left bank slope of Jinping I Hydropower Station.(2)With the decrease of the softening coefficient of the "Water-Level-Fluctuating Zone",the safety factor of the slope decreases gradually.With the expansion of the "Water-Level-Fluctuating Zone",the safety factor of the slope decreases sharply.(3)By regulating the range of "Water-Level-Fluctuating Zone",we can effectively reduce its adverse effects on slope stability.