Analysis On Dynamic Response Of Slab Ballastless Track Subgrade And CFG Pile Net Composite Foundation

The rapid development of China’s high-speed railway constriction calls for the in-depth research of dynamic response,such as strains and stresses of railway subgrade under the load stress of high-speed train,and analysis of dynamic response and load distribution of high-speed railway embankment of soft foundation reinforcement with CFG pile net composite foundation method in railway construction.Using numerical simulation method,The paper analyzes dynamic characteristics of slab ballastless Track Subgrade,and load distribution characteristics of high-speed railway embankment with CFG pile net composite foundation,and discusses influence of geometric and physical mechanical parameters on dynamic characteristics of subgrade,embankment load distribution of CFG pile net composite foundation.Specifics are listed as follows:(1)The train load is simplified as an exciting force functioning as the equivalent axle load.Built on numerical analysis software FLAC3 D,combined with multi-point train loading accomplished by built-in FISH programming language,we simulate the train track structure in mobile loading process,and establish the 3-D dynamic analysis of track subgrade system.The dynamic loading program of computing platform also contributes in calculating the dynamic response of track subgrade structure,gives a detailed analysis of the train subgrade under moving load of each structural layer,and stress response characteristics as well as attenuation features of dynamic response corresponding with subgrade depth,while taking into consideration of different working conditions,such as subgrade stiffness,body stiffness of embankment and the influence pattern of train speed change on subgrade dynamic response.(2)The moving traffic loads are simplified as a plurality of wheel loads.The vibration loads in ground induced by the moving marshalling train were simulated by using multi-support excitation based on time-variation.A theoretical model of track-subgrade system based on slab ballastless track in Sui-Yu Railway Line was presented by employing a 3-dimensional dynamic analysis method,and based on FLAC3 D computing platform,the dynamic response of track subgrade structure is calculated by using the dynamic loading program.The stress path and principal stress axes rotation in the soil elements beneath railway embankment during passages of train loads were studied in detail.(3)Currently,CFG pile net composite foundation method is used in the railway construction in reinforcement of soft foundation,thus raises the possibility of optimum design of high-speed railway considering embankment load distribution angle,load calculation and analysis,stress distribution parameters,embankment height-filling,control results of pile spacing and ratio of embankment height and pile diameter,and the influence of area replacement to pile-soil stress ratio and load sharing the ratio.Besides,the paper analyzes the dynamic response of CFG pile net composite foundation under the influence of vibration load,in particular the dynamic response characteristics of embankment,pile and foundation soil caused by the change of elastic modulus and cushion thickness of subgrade bed,pile and cushion,drawing some meaningful conclusions for engineering design.Above conclusions provides some reference for the further study on dynamic response analysis of the subgrade under moving load and the analysis of the characteristics of the embankment load distribution using CFG pile net composite foundation.