An experimental study of thermal response of saturated red clay subjected to progressively heating and cooling processes

The thermal properties of saturated red clay subjected to progressively heating and cooling processes are experimentally studied under the combining impact of temperature and confining pressure. Two kinds of tests with and without drainage between temperature stages at four confining pressures (50, 100, 150 and 200 kPa respectively) are performed. The temperature is applied sequentially as 20 degrees C -> 40 degrees C -> 50 degrees C -> 60 degrees C -> 70 degrees C -> 80 degrees C -> 70 degrees C -> 60 degrees C...-> 20 degrees C. In this study, the evolutions of temperature, pore pressure, volumetric strain, and the related thermodynamical mechanisms are analyzed. It is shown that during progressively heating/cooling with drainage between temperature stages, the volumetric strain due to the pore pressure dissipation associated with heating are greater than that due to the latter compression induced by negative pore pressure after progressively cooling, and eventually induces an irreversible shrinkage deformation. On the other hand, during progressively heating/cooling without drainage between temperature stages, the pore pressure induced by heating can even reach the applied confining pressure, and then maintains a significant residual pore pressure when the temperature of specimens falls to the initial temperature, revealing also an irreversible thermodynamic processes.