Dynamic Responses Of Soil Slopes Subjected To Seismic Loading

Located in earthquake-prone areas,our country has been focused on seismic resistance of slope.In order to study how different ground motion parameters,geometry and material dynamic parameter impact slope dynamic responses,a QUAKE/W finite element dynamic analysis program was used to establish a homogeneous soil slope model.We selected both cosine waves and natural seismic waves from PEER database.The nonlinear model is used to study the seismic parameters and geometry,and the equivalent linear model is used for the study of the material dynamic parameter.The monitoring points were set in the direction of slope surface,horizontal direction and vertical direction.By analyzing the variation characteristics of PGA,permanent horizontal displacement,shear-strain curve,acceleration response spectrum,displacement time curve and other parameters of the representative region of theearthquake,we explore the dynamic response of soil slope under earthquake action.In the simulation,the ground motion parameters take into account three perspectives of amplitude,spectrum and duration respectively.Geometry is simplified to consider only slope height and slope steepness.The material dynamic parameter is characterized by dynamic shear modulus and damping ratio.The results show that:(1)When vibration intensity of the input dynamic load is small,the shape and spectral value of the acceleration response spectrum of the monitoring points are significantly different and the failure modes is shear fracture in the slope toe before tensile crack on the top.When vibration intensity of the input dynamic load is larger and the predominant frequency of the seismic wave spectrum is similar to the first natural frequency of the slope,the dynamic response values of PGA and horizontal displacement of monitoring points are larger and the failure mode is tensile crack on the top and shear fracture in the toe occur at the same time.Cosine waves tend to regularly increase the displacement time history curve in one single direction.Duration has little effect on the dynamic response of soil slope and it is more meaningful to combined it with the predominant frequency of seismic waves.(2)When slope height increases,the dynamic response of the monitoring point of the PGA amplification coefficient in the horizontal direction,of the change amplitude of the hysteresis curve and of the displacement deformation of the slope shoulder also increases,while the predominant period of acceleration response spectrum is the shortest at the slope shoulder.The larger the steeper slope,the more bellied the hysteresis loop,the more concentrated the stress at the slope toe,and the smaller the shear strength,but has no influence on the predominant frequency of the acceleration response spectrum,only changing the spectral value.(3)When we input the same dynamic load and decrease the damping ratio and/or increase the dynamic shear modulu,PGA response,the maximum horizontal permanent displacement and the maximum shear stress increase.The acceleration response spectra of the monitoring points decreases with the lower damping ratios and increasing dynamic shear moduluses.The prodominant period of response spectrum increases with decreasing damping ratio but decreases with larger dynamic shear moduluses.