Abstract
Robust engineering of geomaterials for energy applications requires a clear understanding of the impacts of temperatures and pressures applied to the soil on their microstructures. Such understandings will facilitate better designs of new geomaterials and technologies via ensuring accurate assessments of the performance of the existing ones. In this study, we assess the changes in the microstructure—specific surface area and pore size distribution—of a saturated clay subjected to stress and temperature cycle. Clay specimens were subjected to the desired mechanical stresses and thermal cycles in a triaxial system. Then, the specimens were swiftly extracted from the triaxial, flush frozen in liquid nitrogen, then freeze-dried to preserve their microstructure. The preserved specimens were then used for specific surface area and pore size distribution assessments using nitrogen (N2)-gas adsorption and mercury intrusion porosimetry. The results established qualitative explanations of the expected microstructural changes in geomaterials under operational conditions, which facilitate the development of new geomaterials that can overcome such alternations.
Highlights
Engineering new geomaterials rely on recognizing the unfavored responses of existing ones under different loading conditions and resolving the associated problems
We identify the thermallyinduced pore structure changes of a saturated clay due to a temperature cycle with the overarching aim to guide the development of new geomaterials or treatments to limit these changes as desired
BET analysis and mercury intrusion experiments were performed on representative samples obtained from the cut soil from the triaxial samples to assess the uniformity of the initial state of microstructure among all triaxial samples
Summary
Engineering new geomaterials rely on recognizing the unfavored responses of existing ones under different loading conditions and resolving the associated problems. We know that thawing frozen clay results in an overall volume contraction associated with reductions in the void ratio [4, 18] Despite this decrease in the void ratio, the hydraulic conductivity of a saturated clay after freezingthaw cycles was reported to increase [19, 20]. Such unexpected contradicting behavior was attributed to changes in soil microstructure due to freezing and thawing [14]. On the other temperature extreme, we know that normally consolidated saturated clays experience thermoplastic contractions upon heating [21, 22] These thermoplastic contractions occur as heating initially develops pore water pressures [23].
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