本文選題：飽和膨脹土　切入點(diǎn)：凍脹試驗(yàn)　出處：《哈爾濱工業(yè)大學(xué)》2016年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：我國(guó)是一個(gè)凍土大國(guó),在世界四大凍土國(guó)中位居第三,凍土主要分布于東北、內(nèi)蒙大部地區(qū)與新疆、青海、西藏部分地區(qū)。隨著我國(guó)多年凍土區(qū)與季節(jié)凍土區(qū)普通鐵路、高速鐵路、快速客運(yùn)專(zhuān)線(xiàn)、高速公路等建設(shè)日益加快,凍害及其防控引起廣泛關(guān)注。目前,季節(jié)凍土區(qū)發(fā)現(xiàn)大范圍膨脹土場(chǎng)地,但是針對(duì)寒區(qū)膨脹土凍脹特性的研究報(bào)道尚且不多。凍土的凍脹變形發(fā)展主要受氣候條件和地下水條件影響,較難預(yù)估其變形大小,有必要研究溫度、補(bǔ)水條件等凍脹敏感性因素對(duì)變形的影響,為減小凍脹對(duì)土工構(gòu)筑物的危害提供理論依據(jù)。本文開(kāi)展了延吉膨脹土基本物理性質(zhì)試驗(yàn)、自由膨脹率試驗(yàn)、土水特征曲線(xiàn)試驗(yàn)和凍脹特性試驗(yàn)等試驗(yàn),重點(diǎn)研究了膨脹土凍脹特性及各因素的影響,基于水-熱耦合理論研究了凍脹變形的計(jì)算方法。這項(xiàng)工作將有助于分析凍土中的傳熱、傳質(zhì)規(guī)律,預(yù)測(cè)凍土在不同邊值條件下的變形,為凍脹量預(yù)測(cè)與防凍害提供一定參考。主要研究工作及重要成果如下:首先,通過(guò)物理性質(zhì)試驗(yàn),獲得膨脹土基本物性指標(biāo);利用自主研制的凍融循環(huán)試驗(yàn)儀FTT1,對(duì)飽和與非飽和土分別開(kāi)展了不同溫度梯度、初始含水率和壓實(shí)度下的凍脹特性試驗(yàn),得到溫度條件是影響開(kāi)放系統(tǒng)下溫度場(chǎng)、水分場(chǎng)以及變形的主要因素之一。試驗(yàn)穩(wěn)定后,溫度沿試樣高度近似呈線(xiàn)性分布,凍脹變形主要由分凝冰引起,主要形成于凍結(jié)緣冷端。其次,基于質(zhì)量守恒、能量守恒等基本定律,在微元體層面建立凍土的水-熱耦合控制方程組,包括能量守恒方程、質(zhì)量守恒方程和聯(lián)系方程,通過(guò)有限元分析軟件建立飽和土的水-熱耦合數(shù)值模型,考慮水分遷移和熱傳導(dǎo)之間的耦合作用,將模擬結(jié)果與試驗(yàn)結(jié)果對(duì)比,驗(yàn)證了模型的正確性。最后,基于分凝勢(shì)理論,分析溫度場(chǎng)各參數(shù)對(duì)水分遷移速率的影響,討論凍結(jié)緣吸力與溫度條件的關(guān)系,引入凍結(jié)緣吸力描述開(kāi)放系統(tǒng)下的補(bǔ)水速率,分析了凍深、凍結(jié)速率和冷端溫度對(duì)水分遷移速率的影響,將凍脹變形區(qū)分為原位凍脹和遷移凍脹兩部分,遷移凍脹占凍脹變形的主要部分,計(jì)算結(jié)果與試驗(yàn)結(jié)果吻合較好。
[Abstract]:China is a great country of frozen soil, ranking third among the four major countries in the world. Frozen soil is mainly distributed in the northeast, most of Inner Mongolia and parts of Xinjiang, Qinghai and Tibet. Along with the permafrost regions in China and the ordinary railways in the seasonal frozen regions, The construction of high-speed railways, high-speed passenger dedicated lines and expressways has been speeding up day by day. Freezing damage and its prevention and control have aroused widespread concern. At present, a large area of expansive soil sites have been discovered in seasonal frozen soil areas. However, there are few reports on frost heave characteristics of expansive soils in cold regions. The development of frost heave deformation of frozen soil is mainly affected by climatic conditions and groundwater conditions, so it is difficult to predict its deformation, so it is necessary to study the temperature. The effect of frost heaving sensitive factors such as rehydration condition on deformation provides a theoretical basis for reducing the damage of frost heave to geotechnical structures. In this paper, the basic physical properties of Yanchi expansive soil and the test of free expansion rate are carried out. The soil water characteristic curve test and frost heave characteristic test, etc., have studied the frost heave characteristic of expansive soil and the influence of various factors. Based on the coupling theory of water and heat, the calculation method of frost heave deformation is studied. This work will be helpful to analyze the law of heat and mass transfer in frozen soil and to predict the deformation of frozen soil under different boundary value conditions. The main research work and important results are as follows: firstly, through physical property test, the basic physical properties of expansive soil are obtained; Using the freeze-thaw cycle tester FTT1 developed by ourselves, the frost heave properties of saturated and unsaturated soils under different temperature gradients, initial moisture content and compactness were tested, respectively. The results show that the temperature conditions affect the temperature field in the open system. One of the main factors of water field and deformation is that the temperature is approximately linearly distributed along the height of the specimen after the experiment is stable, and the frost heave deformation is mainly caused by the freezing ice, which is mainly formed at the cold end of the freezing edge. Secondly, based on the conservation of mass, The basic laws of conservation of energy, such as the conservation of energy, the mass conservation and the relation equation, are established at the level of microelement, and the coupled governing equations of water and heat in frozen soil are established, which include energy conservation equation, mass conservation equation and relation equation. The numerical model of water-heat coupling of saturated soil is established by finite element analysis software. Considering the coupling effect between water migration and heat conduction, the correctness of the model is verified by comparing the simulation results with the experimental results. The influence of temperature field parameters on water migration rate is analyzed, and the relationship between freezing edge suction and temperature condition is discussed. The freezing edge suction is introduced to describe the rehydration rate under the open system, and the freezing depth is analyzed. The effects of freezing rate and cold end temperature on water transfer rate are divided into two parts: in situ frost heave and migration frost heave. The calculated results are in good agreement with the experimental results.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TU443
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本文編號(hào)：1583281