Seismic Response And Reinforcement Method Of Pile Foundation In The Liquefaction Lateral Spread Ground Under Mainshock-aftershock

The results of previous earthquake damage investigation demonstrate that liquefaction lateral spread of soil will cause the damage of pile foundation.Scholars at home and abroad have carried out a lot of research work on the seismic response of bridge piles under the action of the single ground motion,while there are few researches on the seismic response of the piles under the action of Mainshock-Aftershock.Considering that some of the structural damage may occur in the Aftershock,this thesis focuses on the seismic response of the pile foundation under the action of Mainshock-Aftershock.At the same time,because there are a large amount of output and use continuously in our country each year,a mass of slag by conducting dynamic triaxial test,the author aims to investigate the waste slag of liquefiable sandy soil reinforcement effect.Combined with numerical simulation method,slag strengthening methods is discussed under the action of the main sequence of liquefied side effect of flow field seismic response of the pile foundation.The main contents,methods and main findings of this paper are as follows:(1)In this study,a numerical analysis model was established for the pile foundation in the liquefaction side spread flow site under Mainshock-Aftershock.By inputting several groups of Mainshock-Aftershock ground motion combinations at the bottom of the model,it can be concluded that after Mainshock,Aftershock can enhance the displacement of the pile foundation in the liquefaction side spread flow site;Aftershock can increase the pore pressure of soil which has been partially reduced.The time interval between the main aftershock will affect the dissipation of pore pressure,and it has little influence on the displacement and bending moment of pile after Aftershock;(2)Through consolidation undrained cyclic triaxial test,to work out the slag content,cyclic stress ratio and relative density,the initial effective confining pressure effect on the properties of saturated sand liquefaction resistance,according to the test can be obtained: the higher the slag content is,the greater sand liquefaction vibration dynamic load of the cycle time required.The inhibition effect of pore water pressure is rising faster.When the slag content is constant,the larger the cyclic stress ratio is,and the faster the failure rate and pore pressure rise.The greater the relative density of sand is,the higher the initial effective confining pressure is,and the stronger the resistance of sand to liquefaction;(3)By establishing numerical model of triaxial test,completing the sample main physical parameters of calibration,the calibration physical parameters is established based on slag strengthening methods of liquefaction side flow field numerical analysis model of the pile foundation.The study discussed the impact on seismic response of the pile foundation reinforcement depth as well as area,and found that when a certain model of reinforcement area,the greater reinforcement depth is,the better reinforcement effect is;When the reinforcement depth is fixed and the reinforcement area reaches a certain range,the reinforcement effect gradually decreases.This study further deepens the understanding of seismic response law of the pile foundation under the action of Mainshock-Aftershock,and puts forward a reinforcement method based on waste slag.The theoretical and practical significance for objectively understanding the seismic response law of the pile foundation include scientifically improving the seismic design code of the pile foundation in liquefied site to improve the utilization rate of the slag by-product,and reducing the damage effect of the sand liquefaction on the pile foundation.