JRMGE / Vol 15 / Issue 1

Review

Investigation on microstructure evolution of clayey soils: A review focusing on wetting/drying process

Chao-Sheng Tang, Qing Cheng, Xuepeng Gong, Bin Shi, Hilary I. Inyang

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a School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023, China
b Global Education and Infrastructure Services Inc., Charlotte, USA


2023, 15(1): 269-284. doi:10.1016/j.jrmge.2022.02.004


Received: 2021-09-02 / Revised: 2022-01-27 / Accepted: 2022-02-23 / Available online: 2022-04-01

2023, 15(1): 269-284.

doi:10.1016/j.jrmge.2022.02.004


Received: 2021-09-02

Revised: 2022-01-27

Accepted: 2022-02-23

Available online: 2022-04-01


Abstract:

Variability in moisture content is a common condition in natural soils. It influences soil properties significantly. A comprehensive understanding of the evolution of soil microstructure in wetting/drying process is of great significance for interpretation of soil macro hydro-mechanical behavior. In this review paper, methods that are commonly used to study soil microstructure are summarized. Among them are scanning electron microscope (SEM), environmental SEM (ESEM), mercury intrusion porosimetry (MIP) and computed tomography (CT) technology. Moreover, progress in research on the soil microstructure evolution during drying, wetting and wetting/drying cycles is summarized based on reviews of a large body of research papers published in the past several decades. Soils compacted on the wet side of optimum water content generally have a matrix-type structure with a monomodal pore size distribution (PSD), whereas soils compacted on the dry side of optimum water content display an aggregate structure that exhibits bimodal PSD. During drying, decrease in soil volume is mainly caused by the shrinkage of inter-aggregate pores. During wetting, both the intra- and inter-aggregate pores increase gradually in number and sizes. Changes in the characteristics of the soil pore structure significantly depend on stress state as the soil is subjected to wetting. During wetting/drying cycles, soil structural change is not completely reversible, and the generated cumulative swelling/shrinkage deformation mainly derives from macro-pores. Furthermore, based on this analysis and identified research needs, some important areas of research focus are proposed for future work. These areas include innovative methods of sample preparation, new observation techniques, fast quantitative analysis of soil structure, integration of microstructural parameters into macro-mechanical models, and soil microstructure evolution characteristics under multi-field coupled conditions.

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Keywords: Soil microstructure, Pore size distribution (PSD), Wetting/drying cycle, Suction, Volume change

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Chao-Sheng Tang, Qing Cheng, Xuepeng Gong, Bin Shi, Hilary I. Inyang, 2023. Investigation on microstructure evolution of clayey soils: A review focusing on wetting/drying process. J. Rock Mech. Geotech. Eng. 15 (1), 269-284.

Author(s) Information

Chao-Sheng Tang

✉️ tangchaosheng@nju.edu.cn

Dr. Chao-Sheng Tang is currently a Professor and Director of Geological Engineering Division at School of Earth Sciences and Engineering, Nanjing University, China. He obtained his BSc degree from China University of Geosciences (Wuhan) in 2003, and his PhD degree from Nanjing University in 2008. He was Visiting Scholar of University of Cambridge and Ecole des Ponts ParisTech from 2014 to 2016. He is Distinguished Young Scholar by the National Natural Science Foundation of China (NSFC), and Deputy Director of Advanced Computational Engineering Institute for Earth Environment (ACEI). He is Secretary General of the International Society of Environmental Geotechnology (ISEG), and Editorial Board Member of Canadian Geotechnical Journal, Bulletin of Engineering Geology and the Environment, Environmental Geotechnics, and Geoenvironmental Disasters. He was the President of Youth Committee of Engineering Geology in China from 2015 to 2020. His research interests include unsaturated soil mechanics, soil–atmosphere interaction, soil desiccation cracking, bio-geotechnical engineering, optical fiber sensing technique, contaminated soil, and fiber reinforced soil.