煤矸石改良高铁路基填料冻胀特性研究

发布时间：2018-02-25 17:17

本文关键词： 路基填料冻胀试验水-热耦合煤矸石数值模拟　出处：《哈尔滨工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：我国是世界冻土大国,季节性冻土区分布面积超过全国陆地面积的一半。近年来,我国高速铁路建设飞速发展,高速铁路轨道的高平顺性和高稳定性给路基提出了更高要求,而寒区路基填料冻胀引起的轨道不平顺是限制高速铁路发展的重要因素之一。同时,我国煤炭资源丰富,大量矸石山对环境和社会造成巨大影响,对煤矸石进行合理的回收再利用,实现资源的有效合理配置是当前的迫切需求。目前,对高铁路基填料粗粒土冻胀的研究较少,煤矸石在高铁工程中的应用有待推进。据此,本文进行了不同条件下高铁路基填料与煤矸石改良高铁路基填料的单向冻结试验,重点分析了土体在冻结过程中的不同位置处的温度和水分变化,基于水热相互耦合作用建立了考虑气态水迁移的有限元模型,为实际工程中填料冻胀防治给出参考,主要工作及结果如下:(1)自行研制了单向冻融循环试验系统,并在此系统上进行了高铁路基填料单向冻结试验。试验获得了不同初始含水率和水分补给条件下土体的温度、水分变化情况,结果表明:冻结过程开始阶段,高铁路基填料中的降温速率较大,温度迅速降低;冻结后填料中几乎不会形成连续完整的冰透镜体,但在粗颗粒表面会有孔隙冰包裹,同时也会发生明显的正向水分迁移;土体在补水条件下的冻胀量较封闭条件下大,随着土体初始含水率的增加最终冻胀量先变大再减小,在某一中间初始含水率时达到最大。(2)完成了煤矸石改良高铁路基填料单向冻结试验,比较了煤矸石改良高铁路基填料与普通填料在冻结条件下温度和水分变化规律。在冻结条件下,煤矸石填料中温度与水分总体变化规律与普通填料基本一致;但煤矸石改良高铁路基填料在初期降温速率较小,最终冻胀量较相应工况下普通高铁路基填料的最终冻胀量稍大。(3)建立了高铁路基填料冻结水热耦合数值计算模型,并通过试验结果验证了模型的合理性。模型中通过将土体的传质方程、传热方程与联系方程三者联立,实现了冻结过程的水热相互耦合,考虑了气态水迁移和相变潜热,较为合理地描述了路基填料的冻结水热相互作用;通过对水热耦合微分方程进行转化,获得了其所对应等效积分“弱”形式,使数值模型更容易实现收敛。
[Abstract]:China is a large country of frozen earth in the world, and the distribution area of seasonal frozen earth region is more than half of the land area of the whole country. In recent years, the construction of high-speed railway in China has developed rapidly, and the high smoothness and high stability of high-speed railway track have put forward higher requirements for the roadbed. However, the track irregularity caused by frost heaving of roadbed filler in cold region is one of the important factors restricting the development of high-speed railway. At the same time, China is rich in coal resources, and a large number of gangue mountains have a great impact on the environment and society. It is an urgent need to recycle and reuse coal gangue reasonably and realize the effective and reasonable allocation of resources. At present, there are few researches on frost-heaving of coarse grained soil filled with high-speed railway subgrade, and the application of coal gangue in high-speed railway engineering needs to be promoted. In this paper, unidirectional freezing tests of high-speed railway subgrade fillers and coal gangue modified high-speed railway subgrade fillers are carried out under different conditions, and the temperature and moisture changes at different positions of soil during freezing process are emphatically analyzed. Based on the coupling of water and heat, a finite element model considering gaseous water migration is established, which provides a reference for the prevention and treatment of frost heave of fillers in practical engineering. The main work and results are as follows: 1) the unidirectional freeze-thaw cycle test system is developed by ourselves. In this system, unidirectional freezing test of high speed subgrade filler is carried out. The temperature and moisture change of soil under different initial moisture content and water recharge conditions are obtained. The results show that the freezing process begins at the beginning stage. The cooling rate of high speed subgrade filler is large and the temperature is decreasing rapidly. After freezing, there is almost no continuous and complete ice lens in the packing, but there will be pore ice wrapped on the surface of coarse grain, and obvious forward water migration will also occur at the same time. The amount of frost heave of soil under rehydration condition is larger than that under closed condition, and with the increase of initial moisture content of soil, the final frost heave volume increases first and then decreases. The unidirectional freezing test of coal gangue modified high-speed railway subgrade filler was completed when the initial moisture content reached the maximum at a certain intermediate initial moisture content. The variation of temperature and moisture in the coal gangue modified high speed subgrade is compared with that of the ordinary filler under the freezing condition. Under the freezing condition, the general variation law of temperature and moisture in the coal gangue filler is basically the same as that of the ordinary filler. However, the coal gangue modified high-speed railway subgrade filler has lower cooling rate in the initial stage, and the final frost heave volume is slightly larger than that of the ordinary high-speed railway subgrade filler under the corresponding working conditions.) the numerical calculation model of freezing water and heat coupling of the high-speed railway subgrade filler is established. The rationality of the model is verified by the experimental results. In the model, the mass transfer equation, the heat transfer equation and the relation equation are combined to realize the mutual coupling of water and heat in the freezing process, and the gaseous water migration and phase change latent heat are considered in the model. The frozen hydrothermal interaction of subgrade filler is described reasonably, and the equivalent integral "weak" form is obtained by transforming the differential equation of water and heat coupling, which makes the numerical model convergent more easily.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD849.5

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