高速铁路粗粒土路基长期累积变形机理及计算模型研究

Coarse-grained soils are usually used for subgrade filler of high speed railway and the long-term cumulative deformation control and prediction of the subgrade becomes the technical difficult problem in the high speed railway construction, so it’s necessary to reasearch deformation mechanism and calculation model of coarse grained filling under coupling static and dynamic loads.According to dynamic characteristics of subgrade of high speed railway,taking group A or B coarse grained soil as object of study,particle breakage and movement law of subgrade filling are profoundly investigated by applying model test and numerical modeling method in the process of accumulatively deforming and creeping, and the macroscopic and meso-scopic deformation mechanism of subgrade filling will be revealed. The variable can be defined ,which can reflect meso-scopic deformation mechanism of the coarse granular soil filling. The dynamic cumulative strain calculation model would be set up and creep model would be improved,and then the long-term dynamic cumulative strain calculation model would be proposed in consideration of creep effect by coupling strain model and creep model. By the principle of strain continuity, long-term cumulative deformation calculation model will be set up.Finally, spatial-temporal evolution law of subgrade deformation will be analysed deeply,and the conclusions of this project will be verified on the basis of the testing results.The research results of the subject can provide the theory basis and technological guidance for deformation control of coarse-grained soil subgrade of high-speed railway,and yield sound economic and social benefits.

高速铁路路基常采用粗粒土填筑,其长期累积变形控制与预测是高速铁路建造技术的难点，因此有必要对动静荷载耦合作用下粗粒土填料的变形机理和计算模型进行研究。本项目以粗粒土A、B组填料为研究对象，紧密结合高速列车荷载作用下路基动力学响应状态，综合运用模型试验和数值模拟试验方法，研究动静荷载作用下粗粒土填料动力累积变形和蠕变变形过程中颗粒破碎与迁移规律，揭示路基填料变形宏观与细观机理；定义能够反映粗粒土填料变形细观机理的变量，建立动力累积应变计算模型，完善已有的蠕变模型，通过耦合叠加，建立不同应力状态下考虑蠕变效应的粗粒土填料长期动力累积应变计算模型，依据应变连续性原理，构建高速铁路路基长期累积变形计算模型，深入分析列车荷载作用下路基变形时空演化规律，采用模型和现场测试结果对研究结论进行验证。研究成果可为高速铁路粗粒土路基变形控制提供理论依据和技术指导，具有良好的经济和社会效益。

本项目针对高速铁路粗粒土路基长期累积变形问题，首先基于ANSYS平台采用APDL语言建立了无砟轨道路基三维动力有限元模型，模拟8列编组的CRH380A型动车组运行过程，计算揭示了高速列车荷载作用下路基内部动应力时空分布规律及其频谱特性，建立了路基各结构层所受荷载的函数实用表达式；建立了在模型槽内填筑路基模型，采用单点沉降计开展了长期的变形监测，采用双曲线经验模型和开尔文流变模型理论对路基沉降进行预测及参数反分析，结果表明开尔文流变模型预测路基各结构层的变形规律与实测的一致；建立路基标准横断面对称有限元模型，考虑土体的蠕变效应，采用用户子程序法和扩展的D-P塑性耦合模型来建模，采用三参量模型的相关算法和程序来编写开尔文模型的子程序，计算表明基床层、路基本体层和地基层的变形分别为0.50mm、1.35mm、3.60mm，路基累积总沉降为5.45mm。采用大型三轴试验剪切仪，对高速铁路路基粗粒土B组填料的剪胀特性进行试验研究，提出了粗粒土B组填料轴向应变与侧向应变的二次函数关系表达式，建立了粗粒土B组填料关于粗粒含量、围压的剪胀判据方程。开展了粗粒土B组填料的大型动三轴试验，研究了粗粒土动变形及动弹性模量、阻尼特性，建立了能考虑围压、频率等因素影响的动弹性模量及阻尼比关于动应变的关系表达式，粗粒土B组填料的动应力动应变的关系可用Hardin-Drnevich模型描述。采用电动重型击实仪对粗粒土开展了冲击荷载作用粗粒土变形实验，分析了粗粒土受冲击荷载前后颗粒破碎特征，采用分形理论和Marsal颗粒破碎理论分析了粗粒土颗粒变化特征，结果表明粗粒土填料在击实破碎后具有明显的分形特征，粒度破碎分形维数在2.61-2.82之间，黏粒含量相对较多的粗粒土在击实前后颗粒破碎的程度相对较低，分形维数差值相对较小；含水量和黏粒含量是影响粗粒土破碎的两个重要因素，相比较而言，黏粒含量对颗粒破碎的影响更为显著。研究成果可为高速铁路粗粒土路基变形控制提供技术指导。