复杂环境下膨润土膨胀特性研究

发布时间：2018-03-06 07:43

本文选题：膨润土　切入点：膨胀机理　出处：《上海交通大学》2015年硕士论文　论文类型：学位论文

【摘要】：膨润土因其特殊的膨胀特性,低渗透性,常被用作核废料处置库,地下垃圾填埋场的土障材料。它可以吸水膨胀封闭裂隙,自身的低渗透性可以隔绝核废料或污染物与外界环境的联系。但是这些地下处置库填埋场往往处于复杂的地质环境中,这些环境因素会对膨润土的膨胀特性产生较大的影响。为此,本文对膨润土的在复杂环境下的膨胀特性变化进行了全面的研究,本文的主要研究内容如下:(1)从膨润土的膨胀机理和结构特征入手,介绍了双电层模型和分形吸附模型两种膨润土膨胀模型,分析了这两种模型适用性。在此基础上提出一种新的膨润土膨胀力预测模型。该模型分别用双电层模型和分形模型来解释渗透膨胀阶段和晶层膨胀阶段,并通过双电层理论计算得到分形理论中的膨胀系数K,对影响K值因素进行了讨论。(2)详细介绍了膨润土中THMC四场耦合相互作用,并根据四场的相互影响大小,将耦合机制进行了简化。基于前人的THMC多场耦合模型,引入本文推导的新的膨胀模型,重新建立了多场耦合方程。并根据前文关于膨润土的孔隙结构、膨胀机理的讨论结果,建立各个变量之间的耦合本构关系。(3)利用多场耦合模型,模拟了一个核废料处置库中膨润土土障的温度、饱和度、应力、位移等物理量的变化情况。分析了结果对相关参数的敏感性,模拟各种环境因素对膨润土膨胀特性的影响情况。(4)针对化学反应对于膨润土膨胀特性影响的时间尺度较长,建立长时间尺度下饱和膨润土中的化学物质运移反应模型,模拟了长时间尺度下因为化学场作用而导致的膨润土的膨胀性衰减情况。
[Abstract]:Bentonite is often used as a barrier material for nuclear waste disposal depots and landfills because of its special expansion and low permeability. Their own low permeability can insulate nuclear waste or pollutants from the outside environment. But these underground landfills are often in complex geological environments. These environmental factors will have a great impact on the expansion characteristics of bentonite. The main contents of this paper are as follows: (1) based on the expansion mechanism and structural characteristics of bentonite, two kinds of expansion models of bentonite are introduced, namely, double layer model and fractal adsorption model. Based on the analysis of the applicability of the two models, a new model for predicting the expansion force of bentonite is proposed. The model uses a double layer model and a fractal model to explain the permeation expansion stage and the crystal expansion stage, respectively. The coefficient of expansion K in fractal theory is calculated by double layer theory. The factors affecting K value are discussed.) the coupling interaction of THMC four fields in bentonite is introduced in detail, and according to the magnitude of interaction between four fields, The coupling mechanism is simplified. Based on the previous THMC multi-field coupling model, the new expansion model derived in this paper is introduced and the multi-field coupling equation is re-established. According to the results of the previous discussion on the pore structure and expansion mechanism of bentonite, The coupling constitutive relation between various variables is established. (3) by using the multi-field coupling model, the temperature, saturation and stress of bentonite barrier in a nuclear waste disposal bank are simulated. The sensitivity of the results to the related parameters is analyzed, and the influence of various environmental factors on the expansion characteristics of bentonite is simulated. The chemical transport reaction model of saturated bentonite in long time scale was established, and the swelling attenuation of bentonite caused by chemical field in long time scale was simulated.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU443

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