Dynamic Response Analysis And Dynamic Centrifugal Model Test Of Loess

The seismic subsidence characteristics and dynamic vulnerability of natural loess and the large-scale overlap of the loess area with high-intensity areas have caused severe loess seismic subsidence,earthquake landslides and earthquake liquefaction disasters.Because Lanzhou loess has relatively large pores and strong seismic subsidence,this paper takes the loess as the research object,uses FLAC3D to numerically simulate the loess foundation and loess slope,and conducts the dynamic centrifugal model test of the undisturbed loess to study the single The dynamic response law and deformation and failure development law of typical loess foundation and loess slope under horizontal random seismic waves.The acceleration response spectrum,acceleration amplification factor,seismic subsidence and deformation characteristics under different working conditions are analyzed,and the numerical simulation and dynamics are carried out.The centrifugal test was compared to verify the reliability of the research results.The main achievements of this paper include the followings:(1)Acceleration response spectrum of loess site under earthquake action.The response spectrum first increases and then decreases with the increase of the period.The predominant period is between 0.2s and 0.8s.The peak of the response spectrum increases with the increase in elevation.The maximum response spectrum peak of the foundation appears on the surface,and the maximum peak of the slope Appears on the shoulder.(2)Both the loess foundation and the slope have obvious dynamic amplification effect.The acceleration magnification factor of loess foundation gradually increases with the increase of height,and the magnification factor of the ground surface is the largest;the acceleration magnification factor of loess slope gradually increases from bottom to top along the slope surface,and from bottom to top along the slope shoulder plumb line Large,the maximum magnification factor is located at the slope shoulder.(3)The damage pattern of loess site under earthquake action is analyzed.The loess foundation produces obvious seismic subsidence and deformation,and the surface tension cracks develop significantly and penetrate into the foundation,and the middle and lower parts are mainly compressed deformation.The top of the loess slope and the upper middle and upper part of the slope are deformed by earthquakes,while the middle and lower part and the bottom of the slope are deformed by uplift.Tensile cracks on the top of the slope and horizontal dislocation cracks on the slope surface are significantly developed.The slope has only a landslide trend,but no landslide damage occurs.A potential sliding surface is formed inside the slope under the action of strong earthquakes.(4)Water content and seismic load are two major factors that affect the dynamic response of loess sites.With the increase of water content,the shear resistance of the soil decreases,the foundation and slope are seriously damaged under the action of the earthquake,the amount of earthquake subsidence increases,the soil softens,and the dynamic amplification effect decreases;with the increase of the input seismic acceleration peak,The deformation of the soil is larger under the action of larger dynamic shear,the stiffness of the soil is attenuated rapidly,and the dynamic amplification effect is smaller.(5)The acceleration response spectrum,acceleration amplification effect and seismic subsidence deformation development law obtained from numerical simulation and model test are consistent,but there are differences.The numerical simulation is a continuous homogeneous medium,and the acceleration amplification coefficient obtained has good regularity,but it is difficult to reflect the deformation and failure form of the earthquake;the model test uses the undisturbed loess to make the model,its natural cracks are developed,and its structural performance can better transmit the seismic wave energy.The acceleration amplification factor is greater than the numerical result,and the seismic subsidence is smaller than the numerical result.