考虑道砟嵌入作用的有砟轨道基床表层变形行为研究

Study on Deformation Behaviors of Subgrade Bed Surface Layer in Ballast Tracks Considering Ballast Penetration

为研究有砟轨道道砟嵌入现象及其对基床表层变形行为的影响,开展以道砟碎石-基床粉土双层试样为研究对象的动三轴试验,分析道砟嵌入对基床表层变形行为的影响,探讨基于道砟嵌入指标的基床表层变形行为标准。试验结果表明,道砟嵌入使得道砟碎石-基床粉土试样的粉土表层出现道砟槽痕并发生侧向变形,同时承受动荷载的能力降低;提高动应力水平和增加粉土含水率会加剧道砟嵌入程度;道砟碎石-基床粉土试样的破坏模式可分为剪切破坏型和软化破坏型;基床粉土含水率较低时,道砟碎石-基床粉土试样整体变形主要源于道砟和粉土的压缩变形,而当粉土含水率较高时,道砟嵌入引起的轴向和侧向变形则较为显著;当粉土处于最优含水率时,道砟嵌入速率为2.9×10^(-5) mm/s时道砟碎石-基床粉土试样达到塑性安定极限,而当粉土处于天然含水率和饱和含水率时,塑性安定极限对应的道砟嵌入速率则为1.4×10^(-4) mm/s。

Based on the double-layered sample consisting of ballast particles and subgrade soil,a series of dynamic triaxial tests were carried out to study the ballast penetration and the resulting deformation behavior of subgrade surface layer in ballast tracks and to explore the influence of ballast penetration on the deformation behavior and failure patterns of the subgrade surface layer.The failure criterions of the ballast-soil samples were defined based on the ballast penetration rate.The research results show that the ballast penetration induces ballast pockets and lateral deformation of the silty soil and reduces the ability of the sample to resist dynamic loading.The increase in dynamic stress level and subgrade moisture content aggravates the ballast penetration degree.The failure patterns of ballast-soil samples can be divided into shear failure and softening failure.The deformation of the ballast-soil sample is mainly caused by the compression of ballast and soil at the low moisture content of silty soil.The deformation caused by ballast penetration is significant when the moisture content of silty soil is high.For silty soil with optimal moisture content,the plastic stability limit represented by the ballast penetration rate is 2.9×10^(-5) mm/s,and this index changes to be 1.4×10^(-4) mm/s for the samples with natural and saturated moisture content.