基于离散元方法的道床捣固及吹砟维护机理

Maintenance Mechanism of Ballast Tamping and Stone-Blowing Using Discrete Element Method

为从细观上研究捣固和吹砟的维护机理,建立了离散元道砟箱数值模型,并耦合多体动力学的捣固镐模型和计算流体力学的吹砟管模型,对捣固与吹砟的作业全过程进行可视化模拟,基于离散元耦合数值模拟,对比分析了2种道床维护方法对道床扰动及作业后轨枕沉降.结果表明:吹砟作业各阶段对道床的扰动和道砟平均接触力均小于捣固,且扰动主要集中在下插阶段,吹砟作业过程中道砟颗粒速度峰值和接触应力峰值仅为捣固的37.5%和38.9%;捣固后,轨枕底部区域密实度提高了约13.6%,轨枕间上部和下部区域密实度分别降低了约21.0%和提高了约4.8%;吹砟后,轨枕底部区域密实度提高了约6.5%,轨枕间上部和下部区域密实度几乎无变化;在轨枕底部吹入碎石,吹砟作业极大地改善了轨枕底的接触状态和应力扩散,轨枕与道砟颗粒接触数增加了约243%,荷载传递更均匀;1000次循环加载后,吹砟作业后的轨枕沉降相较捣固和未维护工况分别减少了约18.1%和44.4%.

In order to study the maintenance mechanism of ballast tamping and stone-blowing from a micro view,a ballast box numerical model using the discrete element method was established,and the whole processes of ballast tamping and stone-blowing were visually simulated by coupling the tamping hammer model of multi-body dynamics and the blowing tube model of computational fluid dynamics.Based on the discrete element coupled numerical simulation,the effects of two ballast maintenance methods on ballast disturbance and sleeper settlement after operation were compared.The results show that the ballast disturbance and the average contact force of the ballast of the stone-blowing are less than those of the tamping,and the disturbance is mainly concentrated in the insertion stage.Moreover,the peak velocity and contact stress of ballast particles during the stone-blowing are only 37.5%and 38.9%of those during the tamping.After tamping,the compactness at the bottom of the sleeper is increased by about 13.6%,and the compactness of the upper and lower areas between sleepers is reduced by about 21%and increased by about 4.8%,respectively.After stone-blowing,the compactness at the bottom of the sleeper is increased by about 6.5%,and the compactness of the upper and lower areas between sleepers is almost unchanged.Due to the stone-blowing beneath the sleeper,the stone-blowing greatly improves the contact state and stress diffusion at the bottom of the sleeper.The contact number between the sleeper and the ballast particles increases by about 243%,which makes the load transfer more uniform.After 1000 cycles of loading,the sleeper settlement after stone-blowing is reduced by about 18.1%and 44.4%respectively compared with tamping and unmaintained conditions.