有砟轨道道砟嵌入对路基服役性能具有显著影响.基于此设计上层为道砟、下层为路基土的单元试样,通过室内动三轴试验和离散元法(discrete element method,简称DEM)数值仿真研究了动荷载作用下道砟嵌入路基土的宏观变形行为和局部变形特征.研究结果表明:在动荷载作用下,道砟与路基土之间仅通过接触面上有限数量的离散接触传递应力,随动应力幅值增加,道砟嵌入深度也不断增加,嵌入深度与动应力呈指数函数变化.道砟嵌入路基土变形过程分为局部挤压阶段、剪切带形成阶段及剪切带发展阶段,道砟嵌入会使得道砟-路基土接触界面的土样孔隙率显著增加,同时也会使得接触界面发生显著的侧向变形.孔隙率较高的饱和试样在较低的动应力作用下会发生翻浆冒泥现象,道砟嵌入导致的路基面孔隙率升高是既有路线发生翻浆冒泥的重要原因,防治翻浆冒泥需重点防止道砟嵌入导致的土样局部孔隙率升高.该研究成果可加深对道砟嵌入现象以及由此引发的路基表层变形行为的认识.
Abstract
The penetration of ballast in ballast track significantly affects subgrade performance.A unit specimen was designed with ballast on top and subgrade soil below.Laboratory dynamic triaxial tests and discrete element method(DEM)simulations were used to study the macroscopic deformation behavior and local deformation characteristics of crushed ballast penetration into soil subgrade under dynamic loads.The results indicate that,under train-induced dynamic loads,the ballast and subgrade soil only transmit stress through a limited number of discrete contacts at the interface.As the dynamic stress amplitude increases,the depth of ballast penetration into subgrade soil also increases,exhibiting an exponential relationship with the dynamic stress.The deformation process of the ballast penetration specimens can be divided into three stages:localized compression,shear band formation,and shear band development.Under train-induced loads,ballast penetration significantly increases the porosity of soil samples near the ballast-subgrade interface,and causes significant lateral deformation at the contact interface.Saturated specimens with higher porosity can experience mud pumping under relatively low dynamic stress.The increase in subgrade surface porosity caused by ballast penetration is a significant factor contributing to mud pumping in existing railways.Prevention of mud pumping should focus on preventing the local increase in subgrade porosity caused by ballast penetration.The findings deepen our understanding of the ballast penetration phenomenon and the resulting deformation behavior of the subgrade surface.
维普
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