Experimental study on mode I and mode II fracture properties of heated sandstone after two different cooling treatments

In order to investigate the fracture characteristics of heated sandstone after rapid water-cooling and natural air-cooling treatments, many fracture experiments were conducted by using cracked straight-through Brazilian disk samples. Meanwhile, the degradation damage mechanism was discussed. Finally, the experimental results were evaluated based on several modified fracture criteria. The results indicated that sandstone’s fracture toughness decreased with increasing temperature after two cooling treatments. After rapid water-cooling with heating temperatures of 100 and 300 °C, the pure mode I fracture toughness and pure mode II fracture toughness were respectively reduced by 23.9%, 32.1%, and 24.6%, 33.3%. It also revealed that rapid water-cooling had more significant deterioration damage on sandstone’s fracture strength than natural air-cooling. Furthermore, an excellent linear relation of KIIC=1.494KIC of the tested sandstone was observed. Moreover, the strain-based generalized maximum tangential strain criterion provided more accurate theoretical predictions when compared with the stress-based and energy-based criteria.