Effects of Temperature on the Relationship between Mode-I Fracture Toughness and Tensile Strength of Rock

Abstract

Fracture toughness is used to characterize rock resistance to fracturing and it is important in theoretical research and engineering applications. Mode-I fracture toughness can be predicted on the basis of an empirical relationship between fracture toughness (KIC) and tensile strength (σt). In underground engineering, rocks are often subjected to different temperatures. Therefore, this paper explores the effect of temperature on the relationship between mode-I fracture toughness and tensile strength. The results show that the change trends in the KIC and σt values of rocks at temperatures from 20 °C to 600 °C are broadly consistent with each other. For rocks heat-treated to the same temperature, the KIC of the rock increases with an increase in σt. This positive correlation between KIC and σt is different in rocks heat-treated to different temperatures. Critical crack propagation radius (rIC) is an important factor in the relationship between KIC and σt and is related to the type of rock and the conditions under which it is tested. For the same rock, rIC is quite different after it has been exposed to different temperatures. The positive correlation between KIC and σt results from a similarity in the fracture morphology and properties of failure when rock is destroyed in fracture and tensile tests.