独立控制孔隙比和应力状态下对脱—吸湿SWCC的影响

发布时间：2018-02-27 18:23

本文关键词： 非饱和土土水特征曲线基质吸力孔隙比应力状态　出处：《武汉理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：土水特征曲线(SWCC)是表示土中吸力与水分之间关系的曲线,反映了非饱和土中水相的能量与其质量或体积之间的关系,影响着非饱和土的渗透、变形、强度等特性,是描述非饱和土性状的重要工具。但一般由室内测定的土的SWCC和实际情况之间还存在较大的差别,主要体现在土体受的应力状态方面。传统的测试方法中,多使用压实土样,测试时试样所受到的净平均应力为零。但是在实际的土工结构中,土一般处于一定的非零净平均应力状态。已有的研究指出,应力状态是SWCC的影响因素。然而,有学者认为,应力状态不同会导致孔隙比不同,而且施加/卸除基质吸力将影响试样的体积,从而影响孔隙比,因此孔隙比才是SWCC的直接影响因素。可见,关于应力状态对SWCC的影响,争论的交焦点在于,到底它是直接原因,还是因为应力和吸力引起孔隙比变化才是直接原因,而应力只是间接原因。本文的研究工作正是围绕这个问题而展开的。在介绍孔隙比和应力状态对SWCC影响方面的研究现状和总结几种常用的SWCC测定方法及其影响因素的基础上,通过专门设计的两组(三个试样)SWCC试验,以期澄清孔隙比和应力状态哪个是影响SWCC的本质因素。两组试验中,一组为试样在相同竖向应力、不同孔隙比下进行脱湿-吸湿试验;另一组为试样在脱湿-吸湿过程中,通过调节试样的竖向应力(即竖向应力不同),使两个试样的孔隙比始终保持相同。本文得到的主要研究成果如下:(1)基质吸力对孔隙比的影响:脱湿过程中,基质吸力增大,土的孔隙比减小;吸湿过程中,基质吸力减小,土发生回弹,孔隙比变大;吸湿完成时,试样的孔隙比无法回到脱湿起点所对应的孔隙比。(2)孔隙比不同时,即使保持竖向应力相同,SWCC的差异也很大。试样脱湿起点处的初始孔隙比越大,进气值就越小;初始孔隙比越小,进气值就越大,试样的持水能力越好。(3)保持孔隙比相同时,竖向应力对脱、吸湿曲线都几乎没有影响。
[Abstract]:Soil water characteristic curve (SWCC) is a curve that shows the relationship between suction and moisture in unsaturated soil, which reflects the relationship between water phase energy and its mass or volume in unsaturated soil, and affects the permeability, deformation and strength of unsaturated soil. It is an important tool to describe the properties of unsaturated soil. However, there is still a big difference between the SWCC and the actual condition of the soil, which is mainly reflected in the stress state of the soil. In the traditional testing methods, compacted soil samples are used more frequently. The net average stress of the test specimen is zero. However, in the actual geotechnical structure, the soil is generally in a state of non-zero net average stress. It has been pointed out that the stress state is the influence factor of SWCC. However, some scholars believe that, Different stress state will lead to different porosity ratio, and applying / removing the matrix suction will affect the volume of the sample, thus affecting the porosity ratio. Therefore, the porosity ratio is the direct influence factor of SWCC. It can be seen that the effect of stress state on SWCC, The focus of the debate is whether it is a direct cause, or whether a change in void ratio due to stress and suction is the direct cause. But stress is only an indirect cause. The research work in this paper is carried out around this problem. Based on the introduction of the research status of the effect of void ratio and stress state on SWCC, and the summary of several commonly used SWCC measurement methods and their influencing factors, Two groups (three samples) were designed to clarify which is the essential factor affecting SWCC. In the two groups, the desiccation-moisture absorption test was carried out under the same vertical stress and different void ratio. The other group is the sample in the process of dehumidification and moisture absorption, By adjusting the vertical stress (i.e. different vertical stress), the void ratio of the two samples remains the same all the time. The main research results in this paper are as follows: the matrix suction increases during the dehumidification process. In the process of moisture absorption, the matrix suction decreases, the soil rebound, and the porosity ratio becomes larger. When the moisture absorption is completed, the porosity ratio of the sample cannot return to the corresponding porosity ratio of the desiccant starting point. Even if the vertical stress is the same, the difference between SWCC and SWCC is very great. The larger the initial void ratio at the beginning of desiccation, the smaller the inlet value, the greater the inlet value is, and the better the water holding capacity of the sample is, when the void ratio is the same, Vertical stress has little effect on desorption and moisture absorption curves.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU43

【参考文献】