基于离散元的冲击荷载下加筋道砟细观研究

Study on micro-mechanical behavior of reinforced ballast under impact loading using discrete element method

为了从细观上探究冲击荷载下加筋材料加固作用机制,通过离散元方法建立道砟颗粒模型,采用平行黏结模型建立土工格栅、土工格室柔性模型;通过对比室内道砟冲击试验和数值模拟结果,从宏观、细观上研究道砟竖向累积沉降和侧向变形,并对道砟应力链分布、颗粒接触和位移等进行细观分析。结果表明:在冲击高度为250 mm时,相较于未加筋道砟,土工格栅加筋道砟的竖向沉降和侧向变形分别减少24.4%和12.7%,土工格室加筋道砟分别减少33.5%和24.0%;由于道砟加固区存在垫层效应,土工格栅和土工格室加筋道砟的颗粒接触数分别增加9.3%和42.6%,平均接触力分别减少5.6%和16.7%;对比道砟颗粒平均位移,土工格栅和土工格室加筋工况相较于未加筋工况分别减少13.3%和21.1%,土工格室加固效果比土工格栅更为显著。

In order to investigate the reinforcement effect of geosynthetics materials under impact loading from a micro view,the ballast particle model was established by the discrete element method,and the geogrid and geocell flexibility models were established by the parallel bond model.By comparing indoor impact tests on ballast and numerical simulation results,this study investigates the vertical cumulative settlement and lateral deformation of ballast from both macro and micro perspectives.The stress distribution,contact,and displacement of ballast are analyzed at a microscopic level.The simulation results show that,under the impact height of 250 mm,compared to unreinforced ballast,the vertical settlement and lateral deformation of geogrid-reinforced ballast were reduced by 24.4%and 12.7%respectively,while those of geocell-reinforced ballast were reduced by 33.5%and 24.0%respectively.Due to the cushion effect in the reinforced area,the contact numbers for geogrid and geocell reinforced ballast increases by 9.3%and 42.6%respectively,while the average contact force decreases by 5.6%and 16.7%respectively.In terms of average particle displacement,the geogrid and geocell reinforced conditions show reductions of 28.2%and 43.6%respectively compared to the unreinforced condition.The reinforcing effect of geocell is more significant than that of geogrid.