| The pile-slab structure has been widely used in subgrade.However,the theoretical research on its application in collapsible loess area is not perfect.This paper takes pile-slab structure in collapsible loess area of passenger railway line in Northwest China as the background,and launches research on shallow buried and continuous pile-slab structure in collapsible loess.Through practice and access to a large number of literature,the data related to deformation of the pile-slab structure are collected and analyzed.Learning the analysis theory and research methods about pile-slab structure,the finite element simulation model of the shallow-buried and continuous pile-slab structure in collapsible loess was established by using the finite element numerical simulation method.The bearing characteristics and settlement mechanism of the shallow-buried and continuous pile-slab structure in the collapsible loess area are systematically studied.The influence of the main design parameters on the structural characteristics is also analyzed.The main contents and research results of this paper are as follows.1.The steps of simplifying the actual engineering into the finite element model are emphatically introduced and the results of the finite element analysis are analyzed.(1)Analysis and Demonstration on the form of pile-slab structure of passenger railway line in Northwest China.Based on the theory of shallow buried continuous pile-slab structure,two forms pile-slab structure of independent pillars type and joist type is simplified in the longitudinal and transverse directions according to the knowledge of structural static mechanics.The internal force of the two structures under load is analyzed by means of MIDAS/CIVIL.Comparison of the results obtained,independent pillars type in the bearer capability and economic aspects than the of joist type.(2)The whole process of building finite element simulation model is introduced in detail,including rational selection of material constitutive models,definition of material property and characteristic parameter,division of grid,setting of constraint condition,construction stage and load conditions.The problems encountered in modeling are solved,and the modeling experience is summarized,which can provide references for the engineering to be simplified into numerical model.(3)This paper analyzes the elastic deformation of the bearing plate under the condition of double-line loading and single-line loading,and studies the regularity of the irregularity of the ballastless track,and compared it with the standard limits.2.The influence of the main design parameters on deformation of the pile-slab structure and track irregularity is studied by using the variable-controlling method.Some reasonable suggestions on the design of shallow buried and continuous pile-slab structure in collapsible loess are put forward.(1)The larger the single span of the load bearing plate,the greater the deflection of the bearing plate,which may not meet the deformation requirements of the standard,the span is too small,the amount of material is not economical.Therefore,the determination of single span of bearing plate should be considered both in terms of safety and economy.(2)The maximum deflection of the rail increases with the increase of the span of the bearing plate,but the deflection of the rail is not even increasing,and the increment is gradually reduced.This is because the increase of the pile diameter reduces the deformation of the bearing plate.However,the larger the pile diameter,the less the effect of the increase of the pile diameter on the flexural deformation of the bearing plate.(3)The deflection of the rail decreases gradually with the increase of the length of the pile,and the maximum deflection of rail curve with pile length showed an downward trend type downhill.When the pile length reaches a certain length,the contribution of increasing the pile length to the decrease in the deflection of the rail is significantly reduced. |
PDF Full Text Request