高速铁路非平顺路基支撑下的线路映射机理及其诱发的不均匀沉降演化研究

Uneven distribution of subgrade support stiffness in the longitudinal direction generates rail irregularity. The dynamic responses of the train and track are thereof magnified and the uneven settlement of subgrade develops, which threatens the running safety of trains and railway performance. The track filtering effect determines the mapping characteristics of the rail irregularities caused by varying support stiffness and uneven settlement. A vehicle-rail-subgrade dynamic coupling model will be developed considering the stochastic distribution of subgrade support stiffness and uneven settlement in the longitudinal direction. Therefore, the mapping mechanism of the subgrade irregularities and the track filtering effect will be revealed, and the relationship between the cut-off spatial frequency and the properties of track bending stiffness and support stiffness will also be determined. Based on the dynamic triaxial tests, the calculation method of soil dynamic modulus and dynamic damping ratio will be developed, as well as that of accumulative plastic strain. Compared with the field measurement, the magnification effect of dynamic responses of the train and track, caused by the varying subgrade support stiffness, will be simulated and reproduced. Then, the generation mechanism and development of subgrade uneven settlement will be revealed. The influence of longitudinal variability of subgrade support stiffness, including the mean value, standard deviation and spatial frequency, on the system dynamic responses and subgrade uneven settlement will be evaluated. At last, the key control factors will be proposed for the engineering solution. Research of this project will provide technical support for the design, assessment and maintenance in high-speed railways.

路基支撑刚度沿线路纵向的不均匀分布会映射至轨面引起不平顺，导致车辆-轨道动力响应的放大和路基不均匀沉降的发展，是攸关列车运行安全和线路性能稳定的重要问题。轨道和弹性支撑层的滤波效应决定了路基面支撑刚度和沉降不平顺的映射特性。本项目通过建立考虑路基支撑刚度和沉降纵向随机分布的列车-轨道-路基动力耦合分析模型，揭示路基面不平顺特征的映射机理和轨道滤波效应，确定截止空间频率与轨道抗弯刚度和弹性支撑层刚度的相关关系；基于室内动三轴试验，提出路基土体动模量、动阻尼比和累积塑性应变的计算方法；结合现场测试，模拟和重现路基支撑刚度纵向随机分布下的列车和轨道路基动力放大现象，揭示路基不均匀沉降的发生机理和发展规律；评估路基支撑刚度纵向分布变异性（均值、标准差和空间频率）对系统动力响应和路基不均匀沉降的影响，提出关键性控制因素和工程处理建议。本项目研究将为我国高铁线路设计和后期评估维护提供技术支撑。

路基支撑刚度沿线路纵向的不均匀分布会映射至轨面引起不平顺，导致车辆-轨道动力响应的放大和路基不均匀沉降的发展，是攸关列车运行安全和线路性能稳定的重要问题。本项目首先研究了黄泛区典型路基填料的静动力特性。通过84组滤纸试验，揭示了高进气值导致土体具有很强的持水性，获得了不同初始压实状态下的饱和度与基质吸力的关系曲线，分别根据MEPDG法和Frendlund&Xing模型确定了土水特征曲线表达式的经验参数；进而建立了黄泛区中高液限黏土路基的平衡含水率及其对应的抗剪强度计算公式。结果表明，黄泛区中高液限黏土路基平衡含水率较最优含水率增加了约4%~8%，导致服役期间的强度和模量较施工状态有很大幅度的降低。土体回弹模量与物理状态和应力水平密切相关，提出了黄泛区中高液限黏土归一化动态回弹模量表达式，土体的回弹应变为34με~2200με，处于变化敏感的小应变水平，归一化动态回弹模量随着应变的增加而快速减小，最大衰减至0.54；最后，对现行规范的土体动态回弹模量预估模型进行了修正，提出了适合黄泛区中高液限黏土的三参数经验公式。建立了考虑路基支撑刚度和沉降纵向随机分布的10自由度高速列车-板式轨道-路基三维有限元模型，揭示了自重应力作用下路基不均匀沉降和刚度不均匀诱发的几何形态映射机理；提出了基于轨道刚度和厚度的等效柔度指标，建立了基于等效柔度定量表征的路基不均匀沉降形式（波长和幅值）轨面几何形态映射率和轨道附加应力计算模型。研究发现，当不均匀沉降波长小于15m、或波长处于15m~20m且沉降幅值超过15mm时，出现轨道结构与路基的脱空。轨道结构和路基损伤的不均匀波长范围分别为：10m~20m和10m~15m且沉降幅值超过15mm。进一步分别研究了路基不均匀沉降和刚度不均匀下不同列车速度的动力响应，建立了列车振动加速度、轨道结构应力与路基不均匀状态的相关关系。基于列车运行安全性、舒适度以及多级养护维修标准，提出了路基不均匀沉降和刚度不均匀的预警值，并提出了提高轨道平顺性的结构优化建议。

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