Temperature effect on water retention curve under high suction and its modeling based on thermodynamics of sorption

The temperature effect on water retention curve under high suction is investigated experimentally and theoretically. Water retention tests are conducted on GMZ bentonite at five temperatures ranging from 20℃ to 100℃. The test results show that the suction equilibrium time, the water retention capacity and the hysteresis of the water retention curve decrease with the increasing temperatures, and the water retention curves at different temperatures are almost parallel to each other. According to the thermodynamics of sorption and the Le Chatelier’s principle, the water adsorption by soil is always an exothermic process, and it is an inevitable phenomenon that the water retention capacity under high suction decreases with the increasing temperatures. Assuming that the adsorption heat is independent on the temperature and the water retention curves at different temperatures are parallel, a model is established to describe the temperature effect on the water retention curve. Comparisons are made between the model predictions and the test results in this work and some literatures. Good agreement of those comparisons shows that the proposed model has the capability to cover the full suction range.