Experimental study on volume change behavior of clay subjected to thermo-mechanical loads

The volume change behavior of a saturated clay subjected to thermos-mechanical loads is investigated by temperature-controlled triaxial tests. A total of three test series are carried out: mechanical loading-unloading test after thermal cycles, mechanical loading-unloading test after heating or cooling to different temperatures. The experimental results show that for the tested clay, the thermally induced irreversible compression strain is accumulated with the number of thermal cycles at a decreasing rate. This temperature history effect can be erased by the mechanical loading. After loading to a new normally consolidated state, the magnitude and the trend of the plastic volumetric strain are similar to those under the initial thermal cycles. The compression and the swelling index are nearly constant at different temperatures. The yield stress at constant plastic volumetric strain decreases with the increasing temperature. The plastic volumetric strain induced by heating has the similar effect on the yield stress as that generated by the mechanical loading, and a unified hardening rule can be used.