双线重载路基动应力分布与扩能适应性评价研究

Evaluation Study of Dynamic Stress Distribution and Capacity Expansion Adaptability of Double-Line Heavy-Haul Subgrade

针对线路未来扩能要求,以朔黄双线重载铁路路基为研究对象,建立轨枕-路基-地基三维有限元模型,模拟分析列车轴重、行车速度和运行模式对路基动应力分布规律的影响,并采用塑性安定极限动应力方法对不同工况下的路基动力稳定性开展适应性评价。结果表明:不同运行模式下,列车于本侧轨道下方路基面引起的动应力沿横向呈“马鞍形”分布,且满载列车运行时会在空载侧路基面引起小幅动应力;荷载作用区内动应力随深度增加逐渐减小,而在荷载作用区域外动应力随深度增加先增后减,满载线钢轨下方动应力传递至基床层底部时衰减量超过70%;满载线钢轨下方路基面动应力随列车轴重和行车速度的增加而线性增大;以0.2倍自重应力线确定路基动应力影响深度,满载线钢轨下方路基在满载单向与双向运行模式下的影响深度为2.80~4.23 m,已超过基床层设计厚度2.50 m,须对路基动力稳定性开展评估。塑性安定极限动应力方法可用于评估不同轴重、行车速度和含水率条件下的重载路基动力稳定性,对评价既有重载铁路路基扩能适应性具有指导和借鉴作用。

Taking the heavy-haul railway subgrade of Shuo-Huang double-line as the research object and considering the future requirements for railway capacity expansion,a three-dimensional finite element model of sleeper-subgrade-foundation was established to conduct a simulation analysis of the influence of the train axle load,travelling speed,and operation mode on the dynamic response distribution.Then the plastic shakedown limit dynamic stress method was employed to conduct relevant adaptability evaluation on the subgrade dynamic stability in different operating conditions.The results show that under different operation modes,the traininduced dynamic stress on the subgrade surface beneath the track on the running side presents a saddle-shaped distribution along the transverse direction.When the full-load train runs,it causes dynamic stress with small amplitude on the subgrade surface on the no-load side.In the load area,the dynamic stress gradually decreases with the depth;while outside the load area,the dynamic stress first increases and then decreases with the increasing depth,and the decrement has exceeded 70% when the dynamic stress beneath the full load rail reaches the bottom of the subgrade.The dynamic stress of the subgrade beneath the full load rail increases linearly with the increase in axle load and the train speed.The influence depth of subgrade dynamic stress was determined by 0.2 times the self-gravity stress line.The influence depth of dynamic stress of the subgrade beneath the full load rail is between 2.80-4.23 m under the influence of full-load unidirectional and bidirectional operation modes,exceeding the design thickness(2.5 m) of subgrade bed layer.Therefore,evaluation of the dynamic stability of the subgrade is required.The plastic shakedown limit dynamic stress method can be employed to evaluate the stability of heavy-haul subgrades with different axle loads,speeds and rates of water content.Such a method can provide guidance and reference to evaluating the capacity expansion adaptability for existing heavy-haul railway subgrades.