Thermo-volumetric deformations of sand–clay mixtures

In this study, the thermo-mechanical and volumetric behaviour of saturated sand–clay mixtures is investigated, focusing on the influence of clay content on compressibility and cumulative deformations over multiple thermal cycles. Oedometric tests under constant temperature conditions reveal the temperature impact on the compressibility and stiffness of sand–clay mixtures. Non-isothermal drained heating tests on saturated sand–clay mixtures with various proportions, subjected to thermal cycles with an amplitude of 30°C under two vertical stress levels (100 and 800 kPa) illustrate the transition from sand-like to clay-like behaviour. At a constant applied vertical stress of 800 kPa, cumulative thermo-volumetric deformations tend to increase with clay content and the number of thermal cycles, with a behaviour that resembles that of fine-grained soils for an apparent fine content of at least 20% (with at least half of this being clay). These findings underscore the critical role of fines, particularly the clay fraction, in governing the thermo-volumetric response of geomaterials, mapping and further validating thresholds for their thermo-mechanical behaviour type.