Fully-coupled Analysis Of The Influences Of Earthquake Intensity And Hydraulic Fill Density On The Seismic Performance Of The Lower San Fernando Dam

Earthquakes are the cause of liquefaction caused by buildings such as foundations and earth-rock dams.As a result,large deformations and damage will occur.in these buildings In the earthquake of San Fernando,California,in 1971,the Lower San Fernando Earth Dam was severely damaged and liquefied.Its structure was completely destroyed.Quantitative research on the dam has practical reference significance for the study of liquefaction of sand mechanism and prevention and remedy of similar engineering problems in the future.According to different situations,this paper carries out numerical simulation of earth dam based on a complete coupling program.The goal is to obtain the difference of the three indicators of displacement,liquefaction and local soil response under different conditions.In this paper,three kinds of seismic intensity are set for the dam,which are respectively the initial strength of the benchmark,0.6 times the benchmark case strength and 0.3 times the benchmark case strength.By calculation,we can get the influence of three different earthquake intensities on the dam result.Because the dam has been completely destroyed,a backpressure platform was added upstream and an initial seismic intensity was entered into the calculation to see if the remedy could withstand the earthquake.Based on the fact that the flow deformation mainly occurs in the hydraulic impounding area upstream of the dam,the effect of different filling densities on the seismic performance of the dam is obtained by changing the density of the upstream hydraulic impoundment.For different input seismic accelerations,the main difference lies in that the dynamic difference in the strongest stage of the earthquake is larger,and when the strongest stage passes,there is almost no difference in deformation.When the seismic intensity reaches liquefaction that causes the soil to liquefy,the main cause of the deformation becomes the magnitude of the driving shear stress that exceeds the residual strength rather than the magnitude of the earthquake.At different fill densities,ie with different residual strengths,the deformations that continue to occur after the earthquake are also different.The initial void ratio of the filling area is different,and the corresponding residual strength is different,then the driving shear force that causes deformation beyond the respective shear strength will also be different.This will make the three examples in the strong earthquake phase will show different trends.The increased downstream backpressure platform in the upstream part of the dam can significantly limit the flow liquefaction deformation in the upstream of the dam,which in turn can significantly reduce the displacement of the dam in the direction of the reservoir.