Study On Seismic Liquefaction Lateral Deformation Of Slow-tilting Site

The investigation of recent earthquake disasters indicates that it is simple to cause severe sand liquefaction when the soil layer contains sand’s geological conditions.The gently sloping site will facilitate sand liquefaction and exacerbate the lateral deformation of soil during liquefaction.Aiming at the dynamic response law of slow-tilting liquefaction sites,the implementation of anti-liquefaction treatment measures within the underground space occupied by the proposed underground structure not only helps to optimize the seismic design of underground engineering,but also provides a reference for the design of treatment improvement plans for liquefaction sites.In this thesis,the law of seismic liquefaction at various inclination angles is studied,the lateral displacement of earthquake liquefaction,and the design of a liquefaction treatment scheme that can improve the liquefaction site under various dip angles.The primary findings and conclusions of the research are as follows:（1）Using FLAC^3D finite difference software,for the gently sloping site,the dynamic time history analysis method is applied,and the influence laws of different dip angles,different seismic wave intensities,and different soil conditions are investigated.The results indicate that the influence of the three factors on the soil layer is primarily concentrated on the ratio of excess pore pressure,vertical displacement,horizontal displacement,and effective stress.The gradual increase in soil dip angle first causes the upward diffusion of the liquefaction zone,which then converges at the base of the slope.In addition,an increase in lateral and vertical displacement will bring the effective stress closer to liquefaction,and a change in dip angle will cause it in the entire site to be unevenly distributed.When PGA=0.3g,sand quickly reaches a state of severe liquefaction.The greater the earthquake intensity and the severity of sand liquefaction,the more severe the excess pore pressure ratio and effective stress,the greater the soil disturbance,and the larger the vertical displacement and horizontal displacement.When the thickness of the overlying soil is a small fraction of the thickness of the liquefied layer,the state with a small initial stress will also result in a high degree of liquefaction,and the vertical deformation and lateral deformation of the soil will increase.The degree of soil liquefaction and deformation will decrease as the proportion of soil thickness increases.（2）In this study,six gently inclined sites with varying dip angles were analysed to determine the appropriate yield acceleration values for different working conditions.The analysis involved utilising the maximum shear modulus,the shear strength change law,and the pore water pressure growth model.A quadratic integral calculation programme was developed calculate the acceleration.The lateral deformation of soil was determined using the rigid-plastic slider method,and the results were compared with those obtained through the dynamic time history analysis method.The empirical observation is that the ultimate displacement yielded by the rigid-plastic sliding block technique across six incline angles is inferior to that produced by the time-history analysis approach.The magnitude of lateral displacement has a significant impact on the accuracy of the rigid-plastic sliding block method’s calculation results.Additionally,variations in soil depth can also result in divergent outcomes.The time-history analysis method yields the most proximate calculation outcomes when the depth of burial is limited and the displacement is minimal.（3）The present study focuses on the optimisation of design schemes for the treatment of liquefied foundation in a site model exhibiting severe liquefaction.Specifically,the drainage method and compaction pile method are optimised and their respective liquefaction treatment effects are compared under varying earthquake intensities.The findings indicate that the implementation of the drainage technique utilising a gravel cushion can significantly mitigate the excess pore pressure ratio and excess pore water pressure between the reinforced region and the adjacent soil.Additionally,the horizontal and vertical displacements are minimised to a limited extent post-treatment,and the efficacy of liquefaction and displacement treatment is enhanced with higher earthquake intensity.On the other hand,the compaction pile reinforcement approach can effectively decrease the excess pore pressure ratio in the reinforced area,with a more pronounced treatment effect observed in the vicinity of the pile body compared to farther distances.The results indicate that the compaction pile treatment yields superior outcomes in terms of vertical and lateral displacement reduction caused by liquefaction,as compared to the drainage scheme treatment.