The Numerical Study On Earthquake Response Of Liquefiable Soil-pile-structure With Contact Surface

Investigations of earthquake damage show that soil liquefaction is one of the most crucial reason that causes earthquake damage.Although pile foundation could resist the settlement caused by liquefaction,some piles were still reported damaged in strong earthquake because of being subjected by the horizontal load.In today's increasingly intensive structures in coastal city,it is imperative to give a method to analyze and to evaluate the seismic response of structures building on the liquefiable ground.In this study,fully coupled dynamic FE time history method was used for analyzing the liquefiable ground,pile foundation and superstructure.At the first part,a series of numerical simulation for the prototype of the centrifuge shaking table test are conducted to study the seismic response of liquefiable soil and pile foundation.The research in this part not only verified the validity of the fully coupled dynamic FE time history method but also carried out a series of parameter analyses of the key factors such as the parameters of soil-pile contact elements.At the second part,the earthquake response of four typical engineering cases building on liquefiable ground are analyzed by the fully coupled dynamic FE time history method which had been verified in the first part.The research contents of the four typical engineering cases including:(1)The analysis of seismic response of saturated liquefiable natural ground and the proper width-depth ratio of the ground that using equal displacement boundary in FE model,(2)The analysis of seismic response and the effect of post-earthquake on saturated liquefiable soil and superstructure using shallow foundations,(3)The analysis of seismic response and the effect of post-earthquake on soil-pile-superstructure in saturated liquefiable ground,(4)The analysis of seismic response and the effect of post-earthquake on soil-pile-superstructure that close to a shield tunnel in saturated liquefiable ground.Due to the initial effective stress of soil plays a critical role in judging the liquefaction,several methods were proposed to consider the initial effective stress of soil for different typical engineering cases which including the effect of excavation by shield in Case 4.Through the two main parts of the numerical study mentioned above,this study not only discovered the regular pattern of liquefied ground(such as acceleration response,effect pore water pressure response and settlement of it)and seismic response of pile foundation with soil-pile contact element,but also found that volume effect of the pile shaft and soil-pile contact element are the key factors in simulating the soil-pile interaction precisely.In the meantime,the study has formed a fully coupled dynamic FE time history method which had been used to analyze the seismic response of soil-pile-superstructure in liquefiable ground successfully,which including the effect of post-consolidation of liquefied soil on pile foundation,superstructure and tunnel.