Experimental Study on the Thermal Healing Effect on Stress-Damaged Granite

To study the thermal healing effect on stress-induced damage of Beishan granite, the host rock of China’s high-level radioactive waste (HLW) geological disposal underground research laboratory, comprehensive experimental works were carried out. The deformation rate analysis test was carried out on granite after different stress levels and different temperature conditions (room temperature and mild temperature, 150 °C). Results showed that the deformation memory to the previous stress loading (stress damage) was fading after mild temperature treatment, and the Kaiser effect was also faded notably that AE activity was suppressed after mild temperature treatment, which implied stress-induced damage was recovered under mild temperature. In addition, stress-induced pores, especially large pores, were decreased markedly after mild temperature treatment characterized by the nuclear magnetic resonance measurement. Overall, the mild temperature possesses the ability to heal stress ( σ cc to σ ci , σ ci to σ cd ) induced damage. The permeability reduction, strength enhancement, pores decreasing, and the mechanism under mild temperature were jointed analyzed, which is positive for the long-term stability and tightness of the HLW geological repository. Highlights The healing effect of temperature on stress-damaged Beishan granite was studied. The DME of granite after different stress loaded was fading after 150 °C treated. The AE activity was suppressed and the Kaiser effect disappeared after 150 °C treated. The mild temperature exhibits the ability of healing stress-induced damage.