An insight on the thermo-mechanical behaviour of a shale

The most recent developments in the field of geo-energy (CO2 sequestration, enhanced geothermal system technologies and nuclear waste disposal) have highlighted a need to examine the effects of temperature on the mechanical behaviour of shales. This work investigates the thermo-mechanical behaviour of Opalinus Clay in relation to different stress conditions and yield stress ratio (YSR) values and evaluates the impact of temperature on the hydro-mechanical properties of this material. To this end, a focused experimental campaign consisting in high-temperature/high-pressure oedometric tests has been carried out. The results show that the thermo-mechanical behaviour of Opalinus Clay is heavily affected by the YSR. The study of the thermal cyclic behaviour shows that expansive irreversible strains can occur upon first heating at high YSR and that a quasi-reversible behaviour follows during subsequent thermal cycles. A decrease in the yield threshold is observed when compression is applied ...