Seismic Dynamic Response Analysis Of Slope With Liquefiable Layer In Loess Area

The earthquake survey shows that the disaster case in which the earthquake induced the landslide of the liquefied soil slope,causing huge economic losses and casualties,in recent years,seismic landslides have attracted extensive attention.The instability mechanism of such landslides has always been the difficulties and hotspots of the geophysical earthquake.The reproduction of the earthquake dynamic response is an important part of the landslide instability mechanism.Therefore,in order to further clarify the seismic dynamic response law and failure mode of the liquefied layer slope,this paper uses the shake table test model and the numerical simulation,and studies the dynamic response law of acceleration,pore pressure,and failure mode.The main research work and the specific results are as follows:(1)Based on the geological characteristics of the terrace,combined with the geological drilling data,and according to the stratum distribution characteristics and ways of the slope with liquefiable layer in the loess area,the geological model of the slope with liquefiable layer in the loess area is summarized and generalized,which is from bottom to top as sandstone layer,liquefiable sand layer and yellow soil layer.(2)According to the geological model of slope with liquefied soil layer,according to Buckingham?theorem and dimensional analysis method,the 1:10 shaking table test slope model was designed,and the shaking table test of seismic dynamic response of slope with liquefied soil layer was carried out.(3)According to the measured acceleration time history data of the shaking table,the dynamic acceleration amplification effect of the slope with liquefied soil layer is studied.The results show that the liquefiable soil layer has obvious energy dissipation effect,that is,the amplification coefficient increases nonlinearly in the middle and lower parts of the slope,and the acceleration amplification coefficient decreases in the middle and upper parts of the slope,and the surface effect is obvious from the inside to the outside of the slope.With the increase of the peak acceleration,the soil enters the plastic deformation stage,the transmission capacity of seismic waves decreases,and the acceleration amplification coefficient also decreases to a certain extent.(4)For the filtering effect of slope soil acceleration,the Fourier response spectrum and Hilbret-Huang transform analysis results based on acceleration time history show that the amplification effect of acceleration along elevation is related to the filtering of high-frequency components of seismic waves by slope soil.That is to say,with the increase of the peak acceleration,the dominant frequency in the overlying loess first increases and then decreases,and the dominant frequency in the liquefiable sand layer gradually develops to low frequency.In the sandstone in the middle and lower part of the slope,the high frequency components increase,which proves that after liquefaction,the filtering effect of sand is obvious.(5)With the increase of peak acceleration,pore pressure increases.There is a good correspondence between the rapid rise of pore pressure and the peak acceleration of seismic wave in time,but the dissipation process is slightly lagging behind the peak acceleration time.The change trend of the maximum pore pressure ratio is from the lower surface of the liquefaction layer to the upper surface of the liquefaction layer and then to the rear edge of the liquefaction layer.It shows a development model from the surface layer to the deep layer.The greater the burial depth,the greater the pore pressure,and the smaller the pore pressure ratio.(6)The physical and mechanical parameters of soil related to seismic liquefaction are introduced to establish the numerical calculation model of seismic dynamic response of slope with liquefiable layer in loess area.Based on the analysis of displacement and failure mode of FLAC^3D and PFC^2D,it is proved that the greater the peak acceleration is,the more obvious the displacement dynamic response and failure mode.The failure mode of slope with liquefiable layer in loess area is mainly plastic extrusion of liquefiable sand layer and tensile failure of overlying loess.The shear outlet is located at the interface between sandstone and liquefiable sand,and the seismic subsidence of overlying loess is less than that of liquefiable sand.