Journal
CANADIAN GEOTECHNICAL JOURNAL
Volume 54, Issue 5, Pages 700-709Publisher
CANADIAN SCIENCE PUBLISHING
DOI: 10.1139/cgj-2016-0250
Keywords
stiff clays; swelling; suction; microstructure; crack; wetting
Funding
- French Agency for the Management of Nuclear Waste (ANDRA)
- National Natural Science Foundation of China [51478121]
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This paper addresses the microstructure change induced by swelling for natural stiff Teguline clays. The predominant clay mineral measured by X-ray diffractometry was identified to be illite and no swelling clay minerals were found. Significant swelling occurs upon wetting, illustrating the process of suction release from a nearly fully saturated condition. Mercury intrusion porosimetry (MIP) and scanning electron microscopy were used to identify the change in microstructure with swelling during wetting. It is found that the soil swelling mainly leads to an increase of macropores (0.15-350 mu m), and a slight decrease of micropores (0.006-0.15 mu m) and inaccessible pores (<0.006 mu m and >350 mu m). Furthermore, swelling was found to occur in the direction perpendicular to the bedding plane, indicating an anisotropic swelling behaviour. The creation and development of cracks during wetting were also investigated. It appears that most cracks caused by swelling have the size of macropores (0.15-350 mu m) identified by the MIP test. These findings call enough attention to the significant change in microstructure by wetting-induced swelling that can strongly influence the thermohydromechanical properties of stiff clays.
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