纤维改良土的热学和力学性质研究

发布时间：2018-01-19 12:35

本文关键词： 纤维改良土冻融循环试验动三轴试验静三轴试验导热系数试验动/静本构模型热物理统计模型　出处：《北京交通大学》2017年博士论文　论文类型：学位论文

【摘要】：了解纤维改良土的冻结行为对寒区的地基技术、道路与土方工程至关重要。本文的主要目的是:研究纤维改良土在数次冻融循环下的物理、力学、热力学的性质,并利用Stefan方程与改进Berggren方程预测土耳其东部地区的最大冻深。为了完成这个目标,对经历冻融循环后的纤维改良土(随机掺加玻璃纤维、玄武岩纤维、钢纤维、粉煤灰、木质素)的物理性质,如:质量损失、含水量变化与试样高度等指标进行测量。进一步地,纤维改良土的热力学性质总结为与冻融循环次数、纤维含量、温度有关的函数。为了验证试验结果,建立一种热物理统计模型来模拟不同冻融循环、温度条件下的纤维改良土。此外,进行了两大组UU三轴试验来验证纤维改良土的力学性质,试验变量包括:①纤维(玻璃、玄武岩)、纤维含量(0,0.5和1%),冻融循环次数(0,2,5,10,和15),围压(100,200,和300kPa);②纤维与含量(粉煤灰,4和8%;木质素,0,0.25,0.5,0.75和1%),冻融循环次数(0和15),围压(100,200,和300kPa)。使用两种Duncan-Chang双曲线模型预测冻融条件下纤维改良土的静应力-应变关系。此外,进行了动三轴试验,变量为:纤维(玻璃,玄武岩),纤维含量(0,0.5和 1%),围压(300,400 和 500kPa),冻融循环次数(0,2,5,10,和 15)。为了验证冻融条件下纤维改良土的动剪应力、动剪切模量,选用Hardin-Drnevich模型和Kondner-Zelasko模型,建立了剪切模量与冻融次数、纤维含量、围压、初始含水量之间非线性关系。试验结果表明,掺加不同含量的纤维有助于提高地基土的工程性质(冻融条件下的热、力参数),并且不同纤维含量、冻融循环下的纤维改良土的试验结果与数学模型拟合效果优。
[Abstract]:It is very important to understand the freezing behavior of fiber modified soil for foundation technology, road and earthwork in cold region. The main purpose of this paper is to study the physics and mechanics of fiber modified soil under several freeze-thaw cycles. Thermodynamic properties, and the use of Stefan equation and improved Berggren equation to predict the maximum freezing depth in eastern Turkey. Physical properties, such as mass loss, of fiber modified soils (randomly mixed with glass fiber, basalt fiber, steel fiber, fly ash, lignin) after freeze-thaw cycle were studied. Further, the thermodynamic properties of fiber modified soil were summarized as functions related to the number of freeze-thaw cycles, fiber content and temperature. A thermophysical statistical model was established to simulate the fiber modified soil under different freezing and thawing cycles. In addition, two groups of UU triaxial tests were carried out to verify the mechanical properties of the fiber modified soil. The experimental variables include: 1 fiber (glass, basalt, fiber content: 0. 5 and 1), freezing and thawing cycles: 0, 2, 5, 10, and 15, 2, 100, 200, respectively. And 300 KPA; (2) fibre and content (4 and 8% fly ash); The number of cycles of freezing and thawing is 0 and 15, and the confining pressure is 100 ~ 200. Two Duncan-Chang hyperbolic models were used to predict the static stress-strain relationship of fiber-modified soils under freeze-thaw conditions. In addition, dynamic triaxial tests were carried out. The variables are as follows: fiber (glass, basalt), fiber content (0, 0, 0. 5 and 1), confining pressure, 300, 400 and 500 KPA, freezing and thawing cycles. In order to verify the dynamic shear stress and dynamic shear modulus of fiber-modified soil under freeze-thaw condition, Hardin-Drnevich model and Kondner-Zelasko model are selected. The nonlinear relationship between shear modulus and freeze-thaw times, fiber content, confining pressure and initial water content is established. Adding different content of fiber can improve the engineering properties of foundation soil (thermal and mechanical parameters under freeze-thaw condition, and different fiber content). The experimental results of fiber-modified soil under freeze-thaw cycle fit well with the mathematical model.
【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TU43

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