Dynamic Response Characteristics Of CFG Pile Composite Foundation Under High-speed Train Load

CFG pile composite foundation is a new type of foundation reinforcement technology developed in my country after the 1980 s,which has high economy and adaptability and has been widely used in the foundation of construction projects.And in recent years,this new foundation reinforcement technology has emerged in the railway.There are big differences between CFG pile composite foundations in construction engineering and railway: Firstly,the former is a typical rigid foundation and the latter is generally regarded as a flexible load;secondly,the difference between static load and dynamic load;finally,the control criteria for the settlement of the high-speed railway ballastless track after construction: the settlement requirement is stipulated not to exceed 15 mm,and its normative standard is higher than that of construction foundation.According to the existing literature,the research on composite foundations under rigid foundations has been relatively complete,but the research on the characteristics of composite foundations under flexible foundations has not been fully grasped,both in terms of theory and methodological research.In this paper,the method of numerical analysis is used to analyze the dynamic response of the CFG pile composite foundation under the cyclic load of the high-speed rail,and the different measured data are compared and analyzed,and the law and characteristics of CFG pile composite foundation embankment body,subgrade surface layer,subgrade bottom layer and soft soil layer under high-speed railway load are studied.In this paper,and the model establishment and numerical analysis of the characteristics of CFG pile composite foundation are carried out.The validity and rationality of the numerical simulation are verified by comparing the data obtained by the model with the measured data;through the three-dimensional dynamic analysis of the dynamic response process of the CFG pile composite foundation under the action of the train load,the time-history curves of dynamic stress,dynamic displacement and dynamic acceleration of the model are obtained,and their variation laws with depth are analyzed;The influences of the elastic modulus of CFG pile,the elastic modulus of the filling layer,the action time of the dynamic load,the speed of the train and the weight of the train axle on the dynamic characteristics of the system are studied by using the established composite foundation.It is found that the elastic modulus of the pile body has a significant effect on controlling the dynamic displacement;the dynamic response of the model system increases to a certain extent with the increase of the train speed,but the increment is only 1%;the increase of the train axle load has a significant impact on the dynamic response of the model system,and the two are linear.