Study On Dynamic Response Of Slopes Under Coupling Of Earthquake And Groundwater

Groundwater resources in China are rich.A large number of rainfall and widely distributed rivers and lakes have changed the hydrodynamic environment of slopes.At the same time,earthquakes occur frequently in China.The dynamic response of slopes under coupling of earthquake and groundwater has become a key problem in slope design.Based on the finite difference software Flac3 D,the dynamic response laws and deformation damage mechanism of slope under coupling of earthquake and groundwater was researched,and the effect of topography and seismic source on the dynamic response characteristics of waterbearing slopes was also analyzed.Moreover,a study was carried out on a water-bearing slope in Zheduotang area.The main work and results of this paper are as follows.(1)The numerical models of slopes with different groundwater levels are established,and the response characteristics of acceleration,velocity,frequency spectrum and the variation of excess pore water pressure under different seismic actions are studied.In the case of no water,the acceleration amplification coefficient(?)and velocity amplification coefficient(?)of slope have the effects of elevation amplification and the amplification effect of free surface.The spatial distribution of ? is rhythmic.When the slope contains groundwater,the dynamic response is more severe than that of the slope without water.With the increase of groundwater level,the area of ? response weakening in the lower part of slope increases,and the rhythm is stronger,and the spatial distribution of ? is basically unchanged.The natural frequency of slope decreases,and when it's close to the main frequency of ground motions,the amplification effect of Fourier spectrum is significant.At the foot of the slope,the excess pore water pressure is the smallest,but the excess pore water pressure ratio is the largest,which makes slopes easy liquefy.(2)The numerical model of slope under the same water level is established.The effects of slope height,slope angle,amplitude,frequency and impulse on dynamic response of slope are studied.The results show that,with the increase of slope height,PGA and PGV first increase and then decrease,and the ratio of excess pore water pressure gradually decreases.The change of slope angle has a certain influence on the distribution of PGA.With the increase of seismic amplitude,PGA,PGV and excess pore water pressure all gradually increase.With the increase of frequency,PGA increases first and then decreases.The PGA and PGV of the slope under the action of pulse records are equal to original records which are larger than the residual records.However,the excess pore water pressure and excess pore pressure ratio under the action of residual records are equal to the original records which are larger than pulse records.(3)By inputting typical ground motions,the deformation and failure mechanism and stability of the slope under the coupling of earthquake and groundwater are analyzed.The results show that the groundwater has a significant effect on the deformation and failure of slopes.In the case of water,the plastic yield area of the slope is larger,the potential shear slip surface of the slope is deeper.It is concluded that the fundamental cause of slope instability under the coupling of earthquake and groundwater is the result of the combined action of seismic inertia force and excess pore water pressure.Based on the quasi-static method,the critical water level under different slope heights is calculated,and the critical water level prediction model is proposed.(4)Taking a practical engineering slope in the area of Zheduotang as an example,the dynamic response characteristics and deformation failure mechanism of the actual water level and water free working condition of the slope under earthquake are analyzed.The results show that the amplification of PGA and PGV is related to the formation lithology.Compared with the inside of the slope,liquefaction is more likely to occur at the foot of the slope,and the influence of the self-weight stress of the overburden should be paid more attention.In the case of groundwater,the plastic yield area is connected,the horizontal relative displacement is not convergent,the stability number is less than one,and the slope is damaged.