A micro-mechanical insight into the thermo-mechanical behaviour of clays

Di Donna, Alice and Casarella, Angela and Tarantino, Alessandro (2024) A micro-mechanical insight into the thermo-mechanical behaviour of clays. Geomechanics for Energy and the Environment, 38. 100549. ISSN 2352-3808 (https://doi.org/10.1016/j.gete.2024.100549)

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Abstract

The response of fine-grained soils to the combined effects of stress and temperature is a problem of growing concern in geoenvironmental engineering. Unlike most materials, fine-grained soils subjected to heating under drained conditions can exhibit either reversible expansion or irreversible contraction, depending on their loading history. This clay complex thermo-mechanical behaviour is widely reported in the literature, but its origin is still unknown. This paper explores the particle-scale origin of clay thermo-mechanical behaviour and helps to inform constitutive thermo-mechanical models. Clay particle interactions include non-contact forces, which are electrochemical in nature and prevail in face-to-face configuration and contact forces, which are mechanical forces transferred from one particle to another through a contact surface, typical of edge-to-face configuration. Non-contact forces include electrostatic Coulombic forces and van der Waals attractive forces. This paper proposes a combined numerical and analytical approach to quantify the elementary interactions between clay particles. The results are used to interpret typical stress-thermal paths, such as compression tests at different temperatures and heating-cooling cycles at constant mechanical stress. It is concluded that the electrochemical interactions governing the face-to-face particle configuration can only explain the elastic volumetric response of over-consolidated clays subjected to heating. The thermo-plastic behaviour associated with the reduction of the pre-consolidation pressure with temperature and the volumetric plastic compressive strain in response to heating in normally-consolidated clays is attributed to the edge-to-face particle configurations.

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https://doi.org/10.17868/strath.00088353
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