含水率对分散性土抗剪强度特性影响的微观解释

doi:10.13278/j.cnki.jjuese.20200318

摘要/Abstract

摘要： 分散性土作为一种水敏性特殊土，具有遇水失稳解体的特性，该特性对水利和岩土工程极为不利。为了加强分散性土力学强度及力学强度影响机理方面的研究，以吉林西部乾安地区分散性土为研究对象，通过直接剪切试验和扫描电子显微镜（SEM）分别对不同含水率（5.0%~24.0%）的重塑试样的抗剪强度（垂直压力50、100、200和300 kPa）和微观结构进行测试与观察。结果表明：1）含水率的增加会导致剪应力-剪切位移曲线从应变软化向应变硬化转变，过渡区间为8.0%~11.0%，转变优先出现在高垂直压力下。2）随含水率的增加，内聚力总体呈下降趋势，拐点含水率分别为17.0%和23.0%，内摩擦角则表现出减小—增大—减小的规律，拐点含水率分别为11.0%和17.0%；内聚力的变化受盐分赋存状态和含水率共同作用，内摩擦角的变化受内聚力和黏滞阻力共同影响。3）在Na⁺作用下，随含水率的升高，黏粒结合水膜迅速增厚，结构单元体逐渐解体，颗粒的胶结作用逐渐减弱；结构单元体由大颗粒向小颗粒转变，土体孔隙由大孔隙向小孔隙发展。4） SEM图像定量分析提取到的土颗粒结构单元体形态参数与抗剪强度表现出良好的相关性（显著性水平p<0.05），表明抗剪强度的降低是含水率引起分散性土微观结构单元体变化的宏观表现。

关键词: 分散性土, 含水率, 抗剪强度, 微观结构

Abstract: As a special water-sensitive soil, dispersive soil has the characteristics of collapse and disintegration when encountering water, which isnot conducive to water conservancy projects and geotechnical engineering. In order to enhance the research on the mechanical strength as well as the influential mechanism of dispersive soil, in this paper, the dispersive soil in Qian’an area in the west of Jilin Province was taken as the research object,and the remolded soil samples with different water contents (5.0%-24.0%) were tested and observed respectively by direct shear test (under vertical pressures including 50, 100, 200 and 300 kPa) and scanning electronic microscope (SEM). The results show that:1) The increase of water content led to the transformation of shear stress-shear displacement curve from strain-softening to strain-hardening, the corresponding water content in the transition zone was between 8.0% and 11.0%, and the strain-hardening occurred preferentially under higher vertical pressures. 2) With the increase of water content, the cohesion decreased as a whole with the inflection points at 17.0% and 23.0% of water content, while the internal friction angle showed a decreasing-increasing-decreasing pattern, with the inflection points at 11.0% and 17.0% of water content; It is considered that the cohesion change is affected by both salt phase state and water content, while the change of internal friction angle is affected by cohesion and viscous resistance. 3) Affected by Na⁺, with the increase of water content, the clay bound water film thickened rapidly, the structural units disintegrated gradually, the cementation of some particles weakened gradually, the structural units evolved from large particles into smaller ones, and the size of pores reduced. 4) A good correlation exists between the soil shear strength and main morphological parameters of the soil microstructure units obtained from the quantitative analyses on the SEM images (p<0.05), indicating that the decrease of shear strength is the macroscopic manifestation of the changes in the soil microstructure units induced by water content due to soil dispersity.

Key words: dispersive soil, water content, shear strength, microstructure

中图分类号:

TU411

陈剑平, 刘经, 王清, 韩岩, 王加奇, 李兴华. 含水率对分散性土抗剪强度特性影响的微观解释[J]. 吉林大学学报(地球科学版), 2021, 51(3): 792-803.

Chen Jianping, Liu Jing, Wang Qing, Han Yan, Wang Jiaqi, Li Xinghua. Microscopic Interpretation of Water Content Influence on Shear Strength of Dispersive Soil[J]. Journal of Jilin University(Earth Science Edition), 2021, 51(3): 792-803.

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