基于离散元-有限差分耦合方法的格栅加筋道砟力学性能分析

Study on the Mechanical Properties of Geogrid-Reinforced Ballast Based on DEM-FDM Coupling Method

格栅加筋对有砟道床力学性能的改善机理尚不明确。开展柔性边界条件下的道砟压缩试验,并在此基础上采用离散元-有限差分耦合方法,建立精细化格栅加筋道砟仿真模型;采用室内试验与数值仿真相结合的方式,分析格栅加筋对道砟宏观及细观力学性能的影响。结果表明:格栅加筋能有效提升道砟的承载力和抗竖向变形能力,加筋后试样的应变能量密度增加50.0%;格栅能有效限制其周围道砟颗粒的运动,减少道床横向变形,在相同轴向应力作用下最大横向变形减少16.1%,格栅位置处横向变形减少63.2%;格栅加筋可有效提升道床的抗剪强度,加筋后道床水平承载力提高18.8%;铺设格栅能有效增强其上部道床的密实度,建议在超厚道床或线下基础不稳定区段铺设道砟格栅。

The improvement mechanism of the mechanical properties of geogrid-reinforced ballast bed remains unclear in existing research.Compression tests of ballast with deformable boundary were conducted.Based on these tests,the coupling method of discrete element method(DEM)and finite differential method(FDM)was applied to establish a refined simulation model for geogrid-reinforced ballast.By combining laboratory tests results with numerical simulations,the impact of geogrid on the macroscopic and mesoscopic mechanical properties of ballast sample was analyzed.The results show that geogrid can effectively enhance the bearing capacity and resistance to vertical deformation of the ballast,with a 50.0%increase in strain energy density.The geogrid can effectively restrict the movement of surrounding ballast particles,reducing the horizontal deformation of ballast bed.Under the same axial stress,the maximum horizontal deformation is reduced by 16.1%,while the horizontal deformation at the geogrid location is decreased by 63.2%.Geogrid reinforced can significantly improve the shear strength of ballast bed,with a minimum 18.8%increase in lateral strength.Geogrid can effectively increase the compactness of the upper tier of ballast bed.Therefore,geogrid reinforcement can be implemented in the sections with ultra-thick ballast beds or unstable foundations.