岩土力学 ›› 2023, Vol. 44 ›› Issue (2): 442-450.doi: 10.16285/j.rsm.2022.0316

• 基础理论与实验研究 • 上一篇    下一篇

干燥失水条件下膨胀土的细观裂隙演化特征研究

高浩东1, 2，安然1, 2，孔令伟2，张先伟2，雷学文1   

  1. 1. 武汉科技大学 城市建设学院，湖北 武汉 430065；2. 中国科学院武汉岩土力学研究所 岩土力学与工程国家重点实验室，湖北 武汉 430071
  • 收稿日期:2022-03-16 接受日期:2022-04-20 出版日期:2023-02-10 发布日期:2023-02-17
  • 通讯作者: 安然，男，1992年生，博士，讲师，主要从事环境特殊土工程特性与岩土工程方面的研究工作。E-mail: anran@wust.edu.cn E-mail:GhaoHaodongf@wust.edu.cn
  • 作者简介:高浩东，男，1999年生，硕士研究生，主要从事特殊土土力学等方面的研究。
  • 基金资助:
    国家自然科学基金（No. 12102312，No. 41372314）；岩土力学与工程国家重点实验室开放基金项目（No. SKLGME021018）

Evolution characteristics of meso-cracks in expansive soil under desiccating conditions

GAO Hao-dong1, 2, AN Ran1, 2, KONG Ling-wei2, ZHANG Xian-wei2, LEI Xue-wen1   

  1. 1. School of Urban Construction, Wuhan University of Science and Technology, Wuhan, Hubei 430065, China; 2. State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, Hubei 430071, China)
  • Received:2022-03-16 Accepted:2022-04-20 Online:2023-02-10 Published:2023-02-17
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (12102312，41372314) and the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering (SKLGME021018).

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摘要： 干燥失水现象是引起膨胀土裂隙萌生和扩展的关键性因素，裂隙的演化过程对土体结构完整性和地基的长期稳定与安全具有重要影响。为了研究膨胀土干缩裂隙的演化特点，对原状土试样开展显微CT扫描试验，结合图像分析技术获取了土体细观裂隙的二维/三维图像与特征参数，从定性和定量角度分析了干缩裂隙的演化规律。结果表明：三维重构后的数字模型还原了膨胀土在干燥过程中的体积收缩特征，与试样实测的体积有较好的一致性；从显微CT图像中可以提取细观裂隙的量化指标，如裂隙率、裂隙数量、裂隙体积与裂隙结构特征参数等；随着含水率从24.0%下降至12.0%，膨胀土的裂隙率、裂隙体积呈增大趋势，裂隙数量呈减小趋势；根据裂隙的体积和几何形态特征将其分为连通裂隙和独立裂隙，干燥过程中连通裂隙的体积占比显著提高，独立裂隙数量不断减少；球棒模型有效地模拟了膨胀土裂隙的几何形态特征，在干燥失水过程中等效孔隙半径、喉道半径、喉道长度与孔喉配位数均有增大趋势，裂隙连通性显著增强；SEM图像表明细观裂隙的连通与黏土颗粒排列形式、粒间孔隙发育程度等存在重要关联。

关键词: 膨胀土, 干燥失水, 裂隙, 显微CT扫描试验

Abstract:

Desiccation is the key factor causing the initiation and expansion of cracks in expansive soil. The evolution of cracks has an important influence on the integrity of soil structure and the long-term stability and safety of the foundation. In order to study the evolution characteristics of dry-shrinkage cracks in expansive soil, micro-CT scanning tests were carried out on undisturbed soil samples. The 2D/3D images and characteristic parameters of soil meso-cracks were obtained by using image processing technology, and the evolution of dry-shrinkage cracks was analyzed qualitatively and quantitatively. The results showed that the volume shrinkage characteristics of expansive soil in the desiccating process were restored by the 3D reconstructed digital model, which was in good agreement with the measured volume of samples. The quantitative indexes of meso-cracks, such as crack ratio, crack number, crack volume and crack structure characteristic parameters, can be extracted from micro-CT images. With the water content decreasing from 24.0% to 12.0%, the crack ratio and crack volume of expansive soil increased, while the number of cracks tended to decrease. According to the volume and geometric characteristics of cracks, cracks can be divided into connected cracks and independent cracks. During the desiccating process, the volume proportion of connected cracks increased significantly, while the number of independent cracks decreased continuously. The ‘ball-and-stick model’ effectively simulated the geometric characteristics of the cracks in expansive soil. The equivalent pore radius, throat radius, throat length and pore-throat coordination number all tended to increase during the desiccating process, and the connectivity of cracks was significantly enhanced. The SEM images showed that the connectivity of meso-cracks was closely related to the arrangement of clay particles and the development of the pores between particles.

Key words: expansive soil, desiccation and dehydration, cracks, micro-CT scanning test

中图分类号: TU 443
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