The discrete element method(DEM)was used to study the effect of ballast penetration in ballasted tracks on the deformation characteristics of subgrade soil from both macroscopic and mesoscopic perspectives.The shape of ballast particles was reconstructed based on a three-dimensional structured light scanning system,and the refined modeling of ballast particles was realized.Triaxial computational models of a ballast penetration sample and a pure soil sample with a height of 600 mm and a diameter of 300 mm were established based on DEM software PFC 3D V6.0.The finite difference method(FDM)was coupled with DEM to realize the flexible loading of triaxial confining pressure.The simulations of triaxial tests were conducted separately for both samples.The simulation results of the ballast penetration sample and pure soil sample were compared and analyzed to clarify the influence of ballast penetration on the deformation characteristics of subgrade soil.Research results show that at a confining pressure of 30 kPa,the peak strength of the ballast penetration sample is 257 kPa,whereas that of the pure soil sample is 199 kPa.Compared with the pure soil sample,ballast penetration reduces the load bearing capacity of subgrade soil.At shear termination,the volumetric strain of the pure soil sample is-3.24％,while that of the ballast penetration sample is-14.59％,indicating a more pronounced shear dilation effect in the ballast penetration sample.The lateral deformation mechanism of the pure soil sample is different from that of the ballast penetration sample.Bulging deformation in the middle of the pure soil sample occurs because the central region is unconstrained,allowing particles to move freely.The lateral bulging of the surface soil in the ballast penetration sample occurs because ballast penetration at the ballast-soil interface exerts a squeezing action on surface soil particles on both sides.The trend of soil particle coordination number variation is consistent for both types of samples,showing an initial increase followed by a decrease with axial strain and ultimately reaching a plateau.However,the soil particle coordination number of the pure soil sample is significantly higher than that of the ballast penetration sample.The force chains in the pure soil sample develop along the axial direction and are evenly distributed,whereas noticeable contact force concentration occurs at the ballast-soil interface in the ballast penetration sample.1 tab,26 figs,34 refs.
维普
万方数据
