高频循环移动荷载作用下高速铁路非饱和路基填料受力变形特性及预测模型研究

Considerable field monitoring data indicated that high-speed railway embankment materials are often unsaturated through the service life. The current track foundation design procedures often fail to integrate high-speed train, track superstructure, and track substructure into a coupled system when analyzing dynamic stress and deformation responses induced by high-speed train loading within the embankment layers. The variations in environmental factors such as moisture and temperature levels are not paid enough consideration neither. This could result in severe insufficiency in term of understanding the mechanism of how the embankment materials mechanically respond to moving-wheel loading as well as of adequately designing the track structure. To address such deficiencies, this research study is proposed to make the following improvements. First of all, a three-dimensional dynamic finite element model is developed to compute more accurately the complex dynamic responses of embankment materials with the train, rail, embankment and subgrade layers fully coupled. Secondly, an innovative large-scale laboratory repeated load triaxial testing setup is further enhanced to independently control the suction and temperature during testing. It will be used to test commonly used embankment materials for resilient modulus, shear strength, and permanent deformation characteristics under different predetermined suction and temperature levels. Thirdly, the feasibility of including the matric suction as an independent stress variable into the constitutive models of resilient modulus, shear strength, and accumulative plastic strain properties will be investigated. The accuracy of such resulting models will be evaluated by comparing model predictions against data collected from the full-scale track testing facility as well as from field monitoring of in-service high-speed lines. The outcomes of this research study would include improvement to the current track design philosophy and technical guidance for high-speed railway construction and maintenance.

现场监测数据表明路基填料层在服役期内基本处于非饱和状态，现有高速铁路路基设计方法对干湿-冷热循环等环境因素缺乏足够的考虑，且尚未把列车、轨道、路基和地基土作为一个相互影响的有机整体来分析高频循环移动荷载作用下非饱和路基填料层的受力变形规律，因此难以对轨道-路基进行合理的设计。本项目针对温湿度变化影响非饱和路基填料受力变形的本质特征，通过列车-轨道-路基-地基土一体化动力学仿真分析方法，确定路基填料层中动力响应的分布规律；基于控制基质吸力和温度的室内大型动-静三轴试验结果，探明高频循环移动荷载作用过程中温湿度变化与回弹模量、累积塑性变形、抗剪强度之间的内在关系，揭示受力变形的机理与演化规律；进而将基质吸力考虑为应力状态参量，建立能综合考虑应力、基质吸力和温度变化的受力变形预测模型，采用足尺轨道-路基模型试验和现场试验结果对模型进行比对验证。研究成果可为高速铁路路基的设计和养护提供科学依据。

现场监测数据表明路基填料层在服役期内基本处于非饱和状态，现有高速铁路路基设计方法对干湿-冷热循环等环境因素缺乏足够的考虑，且尚未把列车、轨道、路基和地基土作为一个相互影响的有机整体来分析高频循环移动荷载作用下非饱和路基填料层的受力变形规律，因此难以对轨道-路基进行合理的设计。本项目针对温湿度变化影响非饱和路基填料受力变形的本质特征，通过列车-轨道-路基-地基土一体化动力学仿真分析方法，确定路基填料层中动力响应的分布规律；基于控制基质吸力和温度的室内大型动-静三轴试验结果，探明高频循环移动荷载作用过程中温湿度变化与回弹模量、累积塑性变形、抗剪强度之间的内在关系，揭示受力变形的机理与演化规律；进而将基质吸力考虑为应力状态参量，建立能综合考虑应力、基质吸力和温度变化的受力变形预测模型，采用足尺轨道-路基模型试验和现场试验结果对模型进行比对验证。主要研究进展和重要成果如下：1) 建立了高速铁路列车-轨道-路基-地基系统耦合三维数值仿真有限元模型，并考虑了轨道随机不平顺的影响，将计算结果与实测数据进行了比较验证了所建模型的合理性，对高铁列车不同运行状态下粗粒土路基动力响应进行了分析，对比了动应力、动变形、动剪应变在基床不同位置的变化规律，并探讨了轨道支承条件、车辆行驶速度等因素对基床动力响应的影响；2) 通过大型动三轴试验和理论分析，对比研究了不同动应力幅值、围压、压实度、含水量等条件下粗粒土填料的受力变形特性，分析了粗粒土累积塑性应变与循环动载作用次数之间的关系，得出了划分粗粒土动力行为类型的临界荷载计算公式，获取了动剪应变和动弹性模量的变化规律，建立了累积塑性应变与应力条件及物理状态参数的关系模型，建立了包含基质吸力和物理状态参数的抗剪强度、回弹模量和累积塑性变形预测模型，为高铁粗粒土填料动力性能的研究提供了试验数据和预测模型支撑。研究成果可为高速铁路路基的设计和养护提供科学依据。

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