岩土力学 ›› 2023, Vol. 44 ›› Issue (12): 3501-3511.doi: 10.16285/j.rsm.2022.1912

• 基础理论与实验研究 • 上一篇    下一篇

硅藻土的微观结构特征及其对物理性质的影响

徐倚晴1, 2,张先伟1,王港1, 2,刘新宇1, 3,高浩东1, 4   

  1. 1. 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;2. 中国科学院大学,北京 100049; 3. 华中科技大学 土木与水利工程学院,湖北 武汉 430074;4. 武汉科技大学 城市建设学院,湖北 武汉 430065
  • 收稿日期:2022-12-06 接受日期:2023-04-07 出版日期:2023-12-20 发布日期:2023-12-21
  • 通讯作者: 张先伟,男,1982年生,博士,研究员,主要从事特殊土土力学基础研究及工程应用。E-mail: xwzhang@whrsm.ac.cn E-mail:xuyiqing20@mails.ucas.ac.cn
  • 作者简介:徐倚晴,女,1999年生,硕士,助理工程师,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.42372313)

Microscopic structure and its effects on physical properties of diatomaceous soil

XU Yi-qing1, 2, ZHANG Xian-wei1, WANG Gang1, 2, LIU Xin-yu1, 3, GAO Hao-dong1, 4   

  1. 1. State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, Hubei 430071, China; 2. University of Chinese Academy of Sciences, Beijing 100049, China; 3. School of Civil and Hydraulic Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China; 4. School of Urban Construction, Wuhan University of Science and Technology, Wuhan, Hubei 430065, China
  • Received:2022-12-06 Accepted:2023-04-07 Online:2023-12-20 Published:2023-12-21
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (42372313).

摘要: 硅藻土通常形成于湖泊或海洋环境,是一种由黏土矿物和硅藻残骸组成的天然沉积土。硅藻的轻质与多孔性质使硅藻土的物理特性与不含硅藻的细粒土有较大差异,如低密度、大孔隙比、高含水率的特点,其性质指标不能用常规土力学经验公式确定,当前对这类特殊土的研究尚属探索阶段。为了系统认识硅藻土的物理性质,配置不同硅藻含量的混合土,测试粒径组成、相对密度、比表面积、液塑限等指标,调查了硅藻对物理性质的影响,通过扫描电镜试验解析了微观机制。结果表明:土中的硅藻含量增加会引起粉粒成分增加、相对密度降低、同时比表面积与阳离子交换量也会提高;无论孔隙流体含盐量高低,硅藻土的液塑限均随着硅藻含量的增加而增加,并且塑性指数保持几乎不变。微观结构调查发现硅藻土的特殊物理性质主要受控于硅藻的大体积的中空内腔以及较强的储水能力。试验过程中还发现,尽管硅藻土的液塑限值很高,硅藻含量80%及以上的硅藻土却表现为塑性较弱或几乎没有塑性的粉土,说明液塑限值并不能很好地反映硅藻土的塑性性质,目前通用的细粒土分类标准对硅藻土分类是不合理的。该研究可以为硅藻土的岩土工程性质研究提供数据参考和理论支撑。

关键词: 硅藻, 硅藻土, 物理特性, 微观结构, 液塑限, 塑性

Abstract: Diatomaceous soil is a kind of natural sedimentary soil that formed in lacustrine or marine environment, mainly composed of clay minerals and diatom remains. The light weight and high porosity of diatom results in a significant difference of physical properties between diatomaceous soil and common clayey soil without diatom, such as low density, high porosity and high water content. These physical properties cannot be predicted by empirical equations of conventional soil mechanics and still need to be explored. This study measured typical physical indices of particle size composition, specific gravity, specific surface area and Atterberg limits of diatom-kaolin mixtures at different diatom contents to enhance systematical comprehension of physical properties of diatomaceous soil. Also, the scanning electron microscope tests were performed to reveal the microscopic mechanism of these physical properties of diatomaceous soil. The results indicate that increasing diatom content causes increases in silt fraction, specific surface area and cation exchange capacity, and a decrease in specific gravity. As the diatom content increases, the Atterberg limits show ascending tendency with pore fluid being NaCl solutions of different concentrations. Despite both the liquid and plastic limits increase, the plasticity index remains almost unchanged. The microscopic investigation suggests that the abovementioned physical properties of diatomaceous soil mainly depend on the large inner cells and high water-retention capacity of diatoms. The tests also show that diatom-kaolin mixtures with diatom content higher than 80% possess low plasticity or nearly non-plastic during the test despite of the high Atterberg limits of pure diatom. This phenomenon means that the Atterberg limits cannot reflect the plasticity of diatomaceous soil, and the current classification methods for fine-grained soils according to Atterberg limits are inappropriate for diatomaceous soil. This study can provide data reference and theoretical support for research on engineering behaviors of diatomaceous soil.

Key words: diatom, diatomaceous soil, physical properties, microstructure, Atterberg limits, plasticity

中图分类号: 

  • TU411.2
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