软黏土微观定量研究及其应用

发布时间：2018-12-28 12:10

【摘要】：土作为一种工程材料,具有相当复杂的特性,集合了非连续性、非均匀性、力学性质的非线性,但作为一种结构性体,其又具有系统性,其系统内部组成是相互关联和协调的。土体在宏观上表现的一系列物理力学性状均是其内部微细结构的具体表现,其宏观性质在一定程度上受微观结构状态和变化的影响。为进一步了解宏微观之间的联系及其在土力学中的应用,本文在总结国内外软土微观结构研究的基础上,针对软土的微观孔隙率及影响因素、宏微观孔隙率之间的关系、平均接触面积率及其影响因素等问题,利用宏观孔隙率与平均接触面积率之间的关系分析土力学问题,主要研究工作和成果如下： (1)通过对软土的SEM图像扫描,定性分析了其结构孔隙特征,建立了基于Image-Pro Plus (IPP)软件的三维孔隙率计算模型,通过微积分思想,推导了三维孔隙率计算公式,定量统计软土的三维孔隙率。分析了由二值化处理获取的平面孔隙率与本文提出的统计三维孔隙率之间的关系。结果表明：本文提出的三维孔隙计算公式是可行的,较二值化处理获取的平面孔隙率,本文获取的三维孔隙率更加接近孔隙真实情况。 (2)为获取合理的软土微观三维孔隙率,分析了计算步距、放大倍数、阈值大小、分析区域大小等对孔隙率计算结果的影响。研究结果表明：步距越小精度越高,采用步距2有利于兼顾计算容量和精度要求；研究放大倍数宜采用1200±300倍；阈值取值跟放大倍数有关,放大倍数越大阈值也应相应增加；分析区域面积不宜太小,能有效反映整张图像信息的区域面积应占图像总面积的70%以上。 (3)通过对比室内试验获取的宏观孔隙率与计算孔隙率之间的关系,定量获取土体接触面积的百分比,首次提出了软土平均接触面积率的概念,并分析了计算步距、放大倍数、阈值大小、分析区域大小对软土平均接触面积率的影响。结果表明：土体接触面积率的值跟孔隙率有关,孔隙率越大,接触面积率越小,结果符合孔隙分布的客观规律。 (4)为得到软土宏观孔隙率与接触面积率之间的关系,对杭州、宁波和奉化三地的软土进行了大量的SEM图像扫描及室内土工试验,并用本文提出的计算方法,得到了软土孔隙率与平均接触面积率之间的关系,结合数理统计方法,拟合得到了孔隙率与平均接触面积率之间的关系式,定量获得了杭州、宁波及奉化软土的方程参数。 (5)在土的渗透与渗流中考虑土体的接触面积率,得到了考虑接触面积率的土体渗流流速方程,通过考虑接触面积的土体受力微元,推导了渗流中的渗透作用力及渗流出口处的临界水力坡度计算公式,得到渗流出口出的受力稳定由三部分组成,包括渗透力、摩擦力和黏聚力,当不考虑摩擦和黏性时,该式与太沙基式等同。 (6)在固结分析中引入土体的接触面积,考虑土体的固液两相非连续性,推导得到了考虑接触面积的有效应力表达式,包括考虑宏微观关系的太沙基一维固结方程和三维Biot固结方程。 (7)在土压力理论中引入土体颗粒的接触面积,得到考虑接触面积后的水土分算土压力比传统的土压力值要小,并分析了土压力传递的原理,并推导了考虑渗流、超孔隙水压影响的水土分算计算式。 (8)把平均接触面积率引入土坡稳定分析,得到了考虑接触面积大小的边坡稳定分析方法(瑞典条分法和简化毕肖普法),并得到了孔隙率参数对边坡稳定性的影响,结合边坡稳定影响的条件,同时建立了考虑孔隙率影响的坡顶超载、地下水浮力或渗流作用力、地震力作用边坡稳定分析计算式。
[Abstract]:As a kind of engineering material, the soil is a kind of engineering material, and has the characteristics of non-continuity, non-uniformity and mechanical property. However, as a kind of structural body, it also has the systematicness, and the internal components of the system are interrelated and coordinated. A series of physical and mechanical properties of the soil body on the macro level are the concrete performance of the internal micro-structure, and the macroscopic property of the soil body is influenced by the micro-structure state and the change to a certain extent. In order to further understand the relationship between macro and micro and its application in soil mechanics, this paper, on the basis of summarizing the research of the micro-structure of soft soil at home and abroad, aims at the relationship between the micro-porosity and the influencing factors of soft soil and the macro-micro-porosity. The relationship between the average contact area ratio and the average contact area ratio is used to analyze the soil mechanics, and the main research work and results are as follows: (1) By scanning the SEM image of the soft soil, the structure pore of the soft soil is analyzed qualitatively. The three-dimensional porosity calculation model based on the image-Pro Plus (IPP) software is set up, and the three-dimensional porosity calculation formula is derived by the calculus thought, and the three-dimensional pore of the soft soil is quantitatively and statistically analyzed. The correlation between the planar porosity obtained by the two-valued process and the statistical three-dimensional porosity proposed in this paper is analyzed. The results show that the three-dimensional porosity calculation formula proposed in this paper is feasible and the planar porosity obtained by the two-value process is more close to the actual condition of the pores. (2) In order to obtain the reasonable micro-three-dimensional porosity of soft soil, the calculation step distance, the magnification, the threshold size, the size of the analysis area and the like are analyzed and the calculation results of the porosity are analyzed. The results show that the higher the step distance and the higher the precision, it is advantageous to use the step-to-step 2 to balance the calculation capacity and the precision requirement; the magnification factor of the study should be 1200-300 times; the threshold value is related to the magnification factor, the larger the amplification factor and the larger the threshold value should be correspondingly increased, and the area of the analysis area is not It should be too small to effectively reflect that the area area of the entire image information should be 70% of the total area of the image (3) By comparing the relation between the macro porosity and the calculated porosity, the concept of the average contact area ratio of the soft soil is proposed for the first time, and the calculation step distance and the magnification factor are also analyzed., the threshold size, the size of the analysis area, the average contact surface of the soft soil, The results show that the contact area ratio of the soil is related to the porosity, the higher the porosity, the smaller the contact area ratio, and the result is in accordance with the pore distribution. In order to obtain the relation between the macroscopic porosity and the contact area ratio of the soft soil, a large amount of SEM image scanning and indoor geotechnical test of the soft soil in Hangzhou, Ningbo and Fenghua are carried out. The relation between the porosity of the soft soil and the average contact area ratio is obtained, and the relation between the porosity and the average contact area ratio is obtained by using the mathematical statistics method. The relationship between the porosity and the average contact area ratio is obtained by fitting the mathematical statistics method, and the Hangzhou, Ningbo and Fenghua are obtained quantitatively. The equation parameters of the soft soil are given. (5) The contact area ratio of the soil body is taken into account in the seepage and seepage of the soil, and the flow velocity equation of the soil body in consideration of the contact area ratio is obtained, and the seepage force in the seepage and the presence of the seepage outlet are derived by considering the force micro-element of the soil body with the contact area. The calculation formula of the hydraulic gradient of the boundary is that the stress stability obtained by the seepage outlet is composed of three parts, including the penetration force, the friction force and the viscous force, In this paper, the contact area of the soil is introduced in the consolidation analysis, and the non-continuity of the solid solution of the soil is considered, and the effective stress expression considering the contact area is derived, including the one-dimensional consolidation equation considering the macro-micro-relation. and in the soil pressure theory, the contact area of the soil body particles is introduced, the soil pressure of the soil and soil after the contact area is considered is smaller than that of the traditional soil pressure value, the principle of the soil pressure transmission is analyzed, and the seepage and the super-hole are also deduced, (8) The average contact area ratio is introduced into the soil slope stability analysis, and the slope stability analysis method considering the size of the contact area is obtained (the Swedish sub-method and the simplified Bishop method), and the stability of the slope is obtained. The influence of the stability of the slope is combined with the condition of the slope stability. At the same time, the overload of the slope, the buoyancy or the seepage force of the groundwater are established.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU442

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