细观角度研究高速循环荷载作用下有砟道床动力学响应与劣化机理

A frantic jumble geometric deformation and degradation of high-speed railway ballasted track bed have threated driving safety. The repose of the inner mechanism of the high speed railway track geometry deformation and degradation becomes the key problem needed to resolve urgently. The implementation of the project based on discrete element, the finite element and multi-body contact dynamics theory, and combined with experimental study. Project adopts multipoint contact law and elastomer contact law, Hertz contact law, more interface method, multipoint contact and dynamic contact fast search algorithm based on bounding box technology, such as research methods. Project focuses on railway ballasted track dynamics characteristics response under high-speed circulating out-loads. Project involved particularly new mesoscopic mechanics characteristics and its relationship with the geometric deformation and degradation of ballasted track. Project will explore inner relation between new mesoscopic geometrical change of state and railway ballasted track deformation degradation from mesoscopic perspective. Through the establishment of multi-scale, the unified particles body - track structure coupled solution model, project research the coupling mechanism of action between particles body with ballast track structure. Project research goal is to obtain changes in relationships between mesoscopic characteristic of ballasted particles and change of state relations, and to obtain changes in relationships between ballast track state and overall deformation of railway ballasted track. Project implementation has proven interaction mechanism among ballasted particles. Interaction mechanisms affect a frantic jumble overall deformation mechanism of ballasted track. Project goal is to reveal a frantic jumble roadbed deformation and degradation mechanism to the high-speed railway. Finally, the research content solves the mechanism of evolution of high-speed ballasted railway track bed under extreme condition and complicated conditions, and provides stable and reliable theoretical basis for the whole life cycle of a service. Researches have a positive meaning to ensure the driving safety of high speed railway and prolong the service life of the railway ballasted bed.

高速有砟道床几何形变劣化威胁行车安全，其内在机理成为亟待解决的关键问题。项目基于离散元、有限元及多体接触动力学理论，结合试验研究，采用多点接触法则、赫兹接触及弹性体接触法则，多界面、多点接触及基于包围盒技术的动态接触快速搜索算法等研究方法，重点研究高速循环荷载作用下有砟道床动力学响应特别涉及道床细观力学特性及其与道床几何形变劣化的关系，探寻道床细观几何状态变化与形变劣化的内在联系与规律。通过建立多尺度的、统一的颗粒体-轨道结构件耦合求解模型，研究颗粒体道床与轨道结构件之间的耦合作用机制，获取道砟细观特性与道床状态变化的关系及道床状态与道床整体形变内在联系。实现探明道砟相互作用机制及其对有砟道床整体形变的作用机理并揭示高速铁路有砟道床的形变及劣化机理的目标。最终为揭示有砟道床在复杂工况、全生命周期服役下的稳定可靠及演变机理提供理论依据，对确保高速行车安全、延长道床使用寿命有积极的工程意义。

项目以高速有砟道床几何形变劣化威胁行车安全为背景，细观角度研究高速循环荷载作用下有砟道床动力学响应与劣化机理，为揭示有砟道床在复杂工况、全生命周期服役下的稳定可靠及演变机理提供技术支撑。基于球形颗粒模型与Hertz-Mindlin 无滑动接触模型，采用 3D 扫描方法获取多种复杂道砟颗粒边界模型，通过对不同级配方案进行对比分析，提出能满足高速有砟道床建模及高效求解需要的基于簇球颗粒的真实道砟三维离散模型建模方法。基于离散元-有限元耦合建模方法及柔性多体接触动力学理论，建立以多种复杂簇球颗粒级配组成的离散有砟道床与轨道结构件组成的多尺度的、统一的颗粒体-轨道结构件耦合求解模型。针对客货混运的既有高速有砟线路工况，研究了高速循环荷载作用下道床颗粒的振动响应特性，研究了颗粒道床与轨枕底面的接触特性变化，研究了道床整体几何形变及劣化。建立足尺寸1:1室内散体有砟道床循环加载测试试验台，基于加速寿命理论及正交设计方法进行有砟道床全生命周期试验设计，在循环加载试验模型上针对散体有砟道床全生命周期中的振动特性、动力学响应特性、整体几何形变及劣化规律开展试验研究。结果显示：①道床沉降增量与道床振动加速度的平方近似成正比，随着行车速度的增加道床沉降增量随之增加；②轨枕底部与道床的接触强度与沉降增量呈指数增长关系；③道床垂向振动加速度与行车速度之间的拟合曲线接近对数曲线模型，道床横向振动加速度与行车速度之间的拟合曲线接近幂函数曲线模型。通过回归分析法揭示了道床累积沉降与循环加载次数之间符合对数函数曲线变化。建立以循环加载次数为变量的道床初始下沉量的道床沉降计算模型，并以此模型为基础提出散体有砟道床寿命预测评估模型，为实现有砟道床的科学维护管理提供了理论依据。揭示了在外荷载作用下道床整体状态变化、形变劣化的基本规律。