寒区铁路有砟道床动力特性的DEM-FEM耦合方法及高性能计算分析软件

Railway ballasted track mainly consists of sleeper, ballast bed and subgrade. Under repeated train loadings, ballast bed performs non-uniform settlement and reduction of elasticity, influencing the regularity and stability of the track. The freezing of ballast will further aggravate the complexity of the interaction between ballast, sleeper and subgrade under freezing conditions in cold regions, bringing more challenge to the safety of ballasted track in winter. In order to study the dynamic behaviors of railway ballast bed in freezing environment, the discrete element model of ballast is first constructed capable of resembling its real geometric shape, together with the development of the nonlinear contact model considering local equivalent curvature. The freezing effect and failure criteria of ballast under cold conditions are also developed. The shear strength and settlement of ballast bed under freezing condition are analyzed and verified through direct shear and ballast box tests in low temperature lab. Combing the discrete element method (DEM) and the finite element method (FEM), the DEM-FEM model and the solving method with high efficiency are developed next for the interaction of discrete ballast and other continuous structures. Finally, the high performance numerical algorithm based on GPU is studied and computational analysis software is developed. This project provides a theoretical basis for the safety, enhancement and reasonable design of railway ballasted track in cold regions through studies on the dynamic behaviors of ballast bed under freezing condition based on the coupled DEM-FEM model and high performance numerical algorithm.

铁路有砟轨道由轨枕、有砟道床和路基等组成。在列车往复荷载作用下，道床会产生不均匀沉降和弹性降低问题，严重影响轨道结构的平顺性和稳定性。在寒区冰冻条件下，道砟间的冻结现象会加剧道砟颗粒与轨枕、路基间相互作用的复杂性，为冬季有砟铁路的安全运行带来更大的挑战。为研究冰冻环境中有砟道床的动力特性，本申请项目首先构建可表征道砟颗粒真实几何形态的离散单元，发展考虑局部等效曲率的非线性接触模型，并建立道砟颗粒在寒冷风雪下的冻结效应和破碎准则；分析冰冻条件下道砟的剪切强度和动力沉降，并通过低温实验室的直剪和道砟箱试验进行验证；发展道砟颗粒和轨枕、路基相互作用的DEM-FEM耦合模型和高效求解方法，并研发基于GPU并行的高性能数值算法和计算分析软件。本申请项目通过对冰冻天气下有砟道床动力特性的DEM-FEM耦合模型和高性能数值算法研究，可为寒区有砟轨道的安全运行、改良措施和合理设计提供有力的科学依据。

铁路有砟轨道由轨枕、有砟道床和路基等组成，在列车往复荷载作用下会产生道床不均匀沉降和弹性降低问题，严重影响轨道结构的平顺性和稳定性。在寒区冰冻条件下，道砟间的冻结现象将会进一步加剧道砟颗粒与轨枕、路基间相互作用的复杂性，为冬季有砟铁路的安全运行带来更大的挑战。本项目针对“寒区铁路有砟道床动力特性的DEM-FEM耦合方法及高性能计算分析软件”的研究内容，依据申报书中的技术方案和研究计划开展了深入系统的研究，主要完成了以下研究工作：在复杂几何形态道砟颗粒的离散单元构造及非线性接触模型研究中，针对道砟颗粒复杂的几何形态发展了基于球体粘结和Minkowski Sum理论的扩展多面体单元，并建立了适用于不同作用模式的非线性弹-塑性接触模型；在道砟颗粒间的冻结-破碎模型及主要影响因素分析研究中，采用粘结单元模型实现了道砟颗粒间的冻结作用，并建立了冻结道砟颗粒的接触-冻结模型及破坏准则；对冻结道砟材料的单轴压缩和三点弯曲试验检验了离散元模型的可靠性和计算参数的合理性，确定了含水率、温度等对冻结强度的影响；在冰冻条件下道砟材料力学行为的离散元分析及冰冻条件下道砟与枕木、路基相互作用的DEM-FEM耦合模型研究中，分别采用离散元方法模拟冻结的道砟颗粒、有限元方法模拟轨枕和路基，建立了冰冻条件下有砟轨道轨枕-道砟-路基系统的DEM-FEM耦合模型，并发展了基于GPU并行的工程尺度高性能数值算法；建立了单轨枕全尺寸道床离散元模型并分析了道床断面尺寸及轨枕类型对道床横向阻力性能的影响；开展了低温下道床-多层路基动力特性的离散元-有限元耦合模拟，进而确定了低温道床的沉降变形及路基响应特性。由此，本项目通过对寒区铁路有砟道床动力特性的DEM-FEM耦合方法及高性能算法的深入研究，可为寒区有砟轨道的安全运行、改良措施和合理设计提供有力的科学依据。