Study On Stability Of Railway CFG Pile Composite Foundation

High speed trains require high smoothness and stability for subgrade under rails.As a foundation of track structure,roadbed design parameters must be kept within the standard range of basic requirements during operation.This puts forward high requirements for the settlement of high-speed railway subgrade.To achieve this requirement,we must strictly control the post construction settlement of roadbed,especially in soft soil foundation,and how to deal with post construction settlement,so as to minimize the post construction settlement,which is a difficult problem to deal with.A large number of engineering facts also indicate that CFG pile composite foundation is applied to soft foundation reinforcement in high-speed railway engineering for soft soil foundation treatment.This is not only because the CFG pile has lots of advantages,such as high strength,short construction time and high efficiency,but also the main material of the pile is industrial waste,which saves resources to a large extent.Existing research shows that elastic deformation,plastic deformation and compaction settlement of roadbed fill during train running are all limited and controllable as long as they satisfy the filling material and compaction standard of roadbed and basic body.Therefore,how to control the settlement and deformation of the subgrade is the key to control the settlement of the foundation.Taking the section DK37+039.54-DK56+530 of Zhang Hu railway passenger dedicated line as the engineering background,this paper analyzes and studies the CFG pile reinforcement mechanism from the aspects of theoretical research,test and numerical simulation,and studies the settlement of CFG pile composite foundation for passenger dedicated line.The research is mainly from the following aspects:(1)The four aspects of the application of CFG pile composite foundation at home and abroad in soft soil foundation,calculation and research of settlement deformation,numerical simulation and experimental research are reviewed.To analyze the CFG pile stress mechanism and the reasonable thickness of cushion are analyzed.And the calculation method of the bearing capacity in the code and the composite modulus method of composite foundation settlement are briefly summarized.(2)Combined with the engineering geological survey of the typical section of the DK37+039.54-DK56+530 section of the passenger dedicated line of the Zhang Hu railway,the finite element software ANSYS is used to establish the three-dimensional model of the pilegroup.The factors that affect the settlement of CFG pile composite foundation under the static load of subgrade,such as pile length,pile diameter,pile spacing and cushion thickness,are studied and analyzed,and some influence rules are concluded.(3)Taking the CFG pile composite foundation of the DK37+039.54-DK56+530section of the Zhang Hu railway passenger dedicated line as an example,the vertical compression static load test of single pile,the static load test of single pile composite foundation and the pile integrity test are studied and summarized.The finite element software ANSYS is used to simulate the single pile three-dimensional model for the static load test of single pile composite foundation,which is compared with the field experimental data.The results show that the model is reasonable and scientific.This model can be based on the analysis of CFG pile composite foundation.