【作者】 徐进；

【导师】 张家生；

【作者基本信息】 中南大学 ， 土木工程， 2012， 博士

【摘要】 我国列车运行速度不断提高,对铁路路基也提出了更高的要求,充分了解路基的动力响应是高速铁路路基设计和保障铁路运输安全高效的需要。大比例的物理模型试验己成为高速铁路无砟轨道路基结构动力性能研究的重要手段。本文针对目前模型试验的不足建立了高速铁路无砟轨道1：1轨道-路基动力学模型试验系统,并通过数值仿真分析了各因素对高速铁路路基动力响应的影响。主要研究的成果如下：1.针对目前小比例模型试验导致模型试验结果与现场实测存在较大差距的情况,建立了1：1轨道-路基动力学实尺模型试验系统。该系统由反力及动力加载系统,数据测试及采集系统和高速铁路路基模型三部分组成。该系统可以模拟不同因素,例如车型、运行速度、轨道结构类型及状态、环境因素等对高速铁路路基动力响应及累计变形的影响。2.针对高速铁路路基基床表层以下填料难以就地取材,采用试验的方法确定了不良铁路路基填料的改良方案。试验结果表明：(1)随着粗颗粒的增加,最大干密度先增大后减小、最优含水率与之成线性减小；(2)在三轴剪切过程中,填料碎石含量高、低围压下存在剪涨的趋势,碎石含量低、高围压下存在剪缩的趋势；(3)相同碎石含量的填料内摩擦角随着围压的增加而减小,相同围压下内摩擦角随着碎石含量的增加而增大,但当碎石含量大于60%时,内摩擦角的增加速率明显降低甚至不增加。在综合分析各试验结果的基础上,确定碎石掺量为60%的改良料作为路基模型的路基填料。模型填筑施工后检测结果证明改良的填料满足高速铁路路基填筑要求。3.针对目前模型试验只能考虑单轮或者单轴加载,忽略了动荷载的叠加效应,设计了高速铁路模型试验的动力加载装置。该装置的设计基于高速铁路无砟轨道主要由扣件传力这一本质现象,采用多作动器联动来模拟列车动荷载。该动力加载模拟装置既能提供不同轴重,不同列车运行速度下的动力荷载,又考虑了相邻车厢相邻转向架不同轮对之间的动荷载的叠加效应。4.采用有限元分析软件系统分析了高速列车作用下各因素对路基动力响应的影响。分析表明：(1)路基中竖直动应力和竖向动位移随深度呈指数趋势衰减。动应力、动位移经过基床表层分别衰减为约60%、40%,到达基床底面后仅剩余10%左右；(2)路基中基床表层和基床底层的动应力和竖向动位移幅值随列车轴重和行车速度的增加而线性增加,而基床底面(路基深3m处)基本未受影响。(3)混凝土支承层厚度取0.2～0.4m都可满足设计要求,但厚者安全,支承层可采用低标号混凝土以节省造价。基床底层厚度应取2m以上。更多还原

【Abstract】 Higher requirements were needed to the design of subgrade of the railway while the speed of the train continuously increased. Fully understanding the dynamic response of the subgrade was the need for the design of high speed railway subgrade and ensuring safety and high efficiency of the railway transportation. Large scale model test has been the important analysis method to research the dynamic characteristics of the high speed railway subgrade. In this paper, aiming at the disadvantages of the recent model tests,1:1track-subgrade dynamic model test system has been established and how each factor effect the dynamic response of the subgrade under the action of high-speed train has been analysed. The main research results are as follows:1. Aiming at big difference between the small scale model test and in-situ monitering,1:1track-subgrade dynamic model test system was established, which was consist of3parts, counter-force and dynamic loading system, data testing and colletion system and high speed railway subgrade model. The system can be used for simulating how each factor affect the dynamic response and accumulated deformation of the subgrade, such as the type the train, velocity of the train, the type of the track, environment factor and so on.2. Aiming at difficulty in find proper filling in site, experiment research was carried out to determine the improvement plan of unfitted subgrade filling. Test results show that:(1)with the increase of percentage of the coarse particles, maximum dry density firstly increased and then decreased, and the optimum moisture content linearly decreased;(2) in the process of triaxial shear test, high gravel content filling trend to dilate while shearing under the low confining pressure, low gravel content filling trended to shrank while shearing under the high confining pressure;(3) for the same gravel content filling, the internal friction Angle trended to decrease as the confining pressure increase, and under the some confining pressure the internal friction angle trended to increase as the gravel content increase. However, when the gravel content is larger than60%, the rate of the internal friction angle significantly decreased and even no increase. Based on the comprehensive analysis of the results of tests, gravel content is determined by60%. And this improvement filling was adopted to construct the subgrade in the model test. The detected results after model test construction proved that the improved filling met the high speed railway subgrade filling requirements.3. Aiming at the phenomenon that the current model test only use single wheel or single axis to apply loading ignoring the stress superimposition, dynamic loading device was designed for the high speed railway model test. The design was based on essence phenomenon that the fastening conduct the force in the ballastless track of high speed railway, several actuators was set to simulate the train loading. The dynamic loading simulation devices not only could provide dynamic load of different axle load at different speed, but also could consider the superimposition effect of different wheels of adjacent bogie of adjacent car.4. Finite element analysis software was adopted to analyze that how each factor effect the dynamic response of the subgrade under the action of high-speed train. Analysis showed that:(1) vertical dynamic stress and vertical dynamic displacement in the subgrade exponentially attenuated with depth. Through the upper layer of the subgrade, dynamic stress and dynamic displacement respectively attenuated about40%,60%, and only10%left when reaching the bottom of the subgrade;(2) vertical dynamic stress and vertical dynamic displacement amplitude linearly increased as train axle load and train speed increased in the upper and bottom layer of the subgrade. However it was seemed that the bottom of the subgrade (3m deep in subgrade) was unaffected;(3) adopting0.2-0.4m for thickness of concrete bearing layer can meet the design requirements, definitely the thicker is safer, low strength concrete can be used for bearing layer to save the cost. The thickness of the bottom layer of the subgrade should be taken more than2m.更多还原