摘要
引入离散元法(DEM)-有限差分法(FDM)耦合算法对普通铁路碎石道床-土质基床的界面应力进行分析。首先,基于激光扫描以及室内三轴试验,实现碎石道砟颗粒二维精细化离散元建模,并通过设置界面单元进行道砟与土两类不同介质层间速度与力的相互传递,实现离散元法与有限差分法耦合,建立了轨枕-碎石道床-连续土体耦合模型,并通过现场实测结果验证模型的合理性。在此基础上,计算列车通过时耦合模型中基床动应力分布特征,讨论轨枕-道床接触状态对其影响,并将计算结果与轨枕-道床-基床的整体有限元模型的计算结果进行对比。结果表明,轨枕-道床未完全密贴接触状态下,道床中力链呈离散型传递,反之,道床中力链呈向下扩散发展;两种接触状态下,基床表面应力分布差别显著,但是应力峰值接近。耦合模型得到的基床表面应力峰值显著高于有限元模型的计算结果;耦合模型中因道砟散体特性引起的基床表面局部应力集中,在路基中的影响深度约为道砟最大粒径(63 mm)的8倍,即近似基床表层深度。
The discrete element method(DEM)and finite difference method(FDM)coupling algorithm were introduced into the analysis of interface stress between railway ballast bed and soil subgrade.The crushed ballast was simulated by the refined DEM modelling,combined with laser scanning and triaxial testing.Then,an interface element was established between interlayer structure boundaries of ballast bed and subgrade,and consequently the DEM and FDM were dynamically coupled through exchanging the data of forces and velocities between two layers within each time step.Thus,the coupling simulation model was established,which had been validated with the field measured results.On this basis,the characteristics of the dynamic stress distribution of subgrade under the load of one train passing were calculated by the coupling model,and the effect of tie-ballast bed contact state was investigated.The calculated results were compared with the ones derived from the finite element method model of tie-ballast bed-subgrade.The results show that:the force chain in ballast bed is discrete in the coupling model if tie-ballast bed not fully close contact,and on the contrary,the force chain is vertical diffusion;the distributions of subgrade surface stress for the two contact conditions of tie-ballast bed are significantly different,but the stress peak is close for each other.Comparing the stress peak derived from a coupling model and a FEM model,the former is significantly higher than the latter.The influence depth of local stress concentration on subgrade surface caused by irregular ballast was about 8 times as the maximum particle size of ballast(i.e.63 mm),approximating the depth of a subgrade surface layer.
作者
肖军华
张德
王延海
郭佳奇
XIAO Jun-hua;ZHANG De;WANG Yan-hai;GUO Jia-qi(Key Laboratory of Road and Traffic Engineering of the Ministry of Education,Tongji University,Shanghai 201804,China)
出处
《工程力学》
EI
CSCD
北大核心
2018年第9期170-179,共10页
Engineering Mechanics
基金
国家自然科学基金项目(51678447)
高速铁路线路工程教育部重点实验室开放研究基金项目(2015-HRE-03)
关键词
有砟道床
离散元法
有限差分法
耦合算法
基床动应力
ballast bed
discrete element method
finite difference method
coupling algorithm
dynamic stress of subgrade
作者简介
通讯作者:肖军华(1980―),男,湖北人,教授,博士,主要从事铁路路基动力学研究(E-mail:jhxiao@tongji.edu.cn).;张德(1990―),男,江苏人,博士生,主要从事铁路路基动力学研究(E-mail:dz2015@tongji.edu.cn);王延海(1994―),男,安徽人,硕士生,主要从事铁路路基动力学研究(E-mail:2539607905@qq.com);郭佳奇(1993―),男,山西人,硕士生,主要从事铁路路基动力学研究(E-mail:class5126386@163.com).
