Influence of thermal treatment on mode I fracture toughness of certain Indian rocks

An experiment was carried out to measure the static mode I fracture toughness of Manoharpur sandstone, Bellary dolerite and Dholpur sandstone after thermal treatment at different temperatures that ranged from ambient conditions to 600 °C. The three-point bending method was applied using cracks straight through semi-circular bending (CSTSCB) specimens that were fabricated according to International Society for Rock Mechanics (ISRM) standards. Three different rocks were used to measure the degree of influence of thermal treatment on fracture toughness in different rocks. In addition, petrographic and X-ray diffraction (XRD) analyses were carried out to identify the compositions of these rocks. Finally, scanning electron microscope (SEM) analysis was performed in order to measure the micro-cracks that were induced within these rocks as a result of thermal treatment. The experimental results demonstrated that, up to a temperature range of 100 °C, the fracture toughness of Manoharpur sandstone, Bellary dolerite and Dholpur sandstone increased by 40%, 25% and 65%, respectively, when compared to the ambient condition, and thereafter decreased with a gradual increase of temperature. At 600 °C, when compared to the ambient condition, the fracture toughness of these rock types decreased by 59%, 36% and 30% for Manoharpur sandstone, Bellary dolerite and Dholpur sandstone, respectively.