Thermo-mechanical behaviour of a compacted swelling clay

Compacted unsaturated swelling clay is often considered as a possible buffer material for deep nuclear waste disposal. An isotropic cell permitting simultaneous control of suction, temperature and pressure was used to study the thermo-mechanical behaviour of this clay. Tests were performed at total suctions ranging from 9 to 110 MPa, temperatures ranging from 25°C to 80°C, and isotropic pressures from 0·1 to 60 MPa. It was observed that heating at constant suction and pressure induces either swelling or contraction. The results from compression tests at constant suction and temperature showed that, at lower suction, the yield pressure was lower, and the elastic compressibility and plastic compressibility parameters were higher. By contrast, at a similar suction, the yield pressure was slightly influenced by the temperature, and the compressibility parameters were insensitive to temperature changes. The thermal hardening phenomenon was equally evidenced by following a thermomechanical path of loading–heating–cooling–reloading.