Freeze-thaw impact on macropore structure of clay by 3D X-ray computed tomography

• Published in: Engineering geology Vol. 280; p. 105921
• Main Authors: Fan, Wenhu, Yang, Ping, Yang, Zhaohui (Joey)
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2021
• Subjects: Fissure; Freeze-thaw (F-T); Image processing; Lean clay; Macropore; Three-dimensional X-ray computed tomography; Lean clay; Freeze-thaw (F-T); Three-dimensional X-ray computed tomography; Image processing; Fissure; Macropore
• ISSN: 0013-7952; 1872-6917
• DOI: 10.1016/j.enggeo.2020.105921

The change of soil macropores, especially fissures, due to freeze-thaw (F-T) has important implications for soil engineering properties such as hydraulic conductivity and compressibility. This paper describes a quantitative study of the soil macropore changes due to F-T by using three-dimensional (3D) X-ray Computed Tomography (CT). Saturated lean clay specimens were subjected to unidirectional F-T under different water-supply conditions for acquiring 3D X-ray CT images before and after F-T. The CT imagery data were filtered and processed for obtaining parameters such as transverse-sectional macro-porosity, macropore size, transverse-sectional fissure porosity, and longitudinal-sectional fissure orientation frequency distribution. It was found that F-T alters the transverse-sectional macro-porosity and macropore size significantly, the changes are different across the specimen height. Moreover, the changes in the transverse-sectional fissure porosity and longitudinal-sectional fissure orientation frequency distribution vary along with the specimen height. More horizontal fissures form in the unfrozen zone or near the freezing front, depending on water-supply conditions. Pore water pressure data confirm that, besides water migration, soil particles also migrate from the unfrozen zone to the freezing front during freezing with water-supply due to piping. The macropore structural changes help understand the F-T impact on soil engineering properties such as hydraulic permeability and compressibility. •Describe the filtering and processing of CT images to reveal macropore changes of clay.•Freeze-thaw increases the transverse-sectional macro-porosity and macropore size.•The fissure porosity and fissure orientation vary along with the specimen height.•Reveal that soil particles migration due to piping during freezing.