An Experimental Study of the Relation between Mode I Fracture Toughness, K(Ic), and Critical Energy Release Rate, G(Ic)

The construction of the relation between the critical energy release rate, [Formula: see text] , and the mode I fracture toughness, [Formula: see text] , is of great significance for understanding the fracture mechanism and facilitating its application in engineering. In this study, fracture experiments using NSCB and CCCD specimens were conducted. The effects of specimen sizes, loading rate and lithology on the relation between [Formula: see text] and [Formula: see text] were studied. [Formula: see text] was calculated by integrating the load–displacement curve according to Irwin’s approach. Based on the measured [Formula: see text] and [Formula: see text] of the rock specimens, a relation between [Formula: see text] and [Formula: see text] was found to be different from the classical formula under linear elasticity. It was found that both specimen size and loading rate do not influence this relation.