Abstract

The construction of the relation between the critical energy release rate, 𝐺𝐼𝑐, and the mode I fracture toughness, 𝐾𝐼𝑐, 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 𝐺𝐼𝑐 and 𝐾𝐼𝑐 were studied. 𝐺𝐼𝑐 was calculated by integrating the load–displacement curve according to Irwin’s approach. Based on the measured 𝐾𝐼𝑐 and 𝐺𝐼𝑐 of the rock specimens, a relation between 𝐺𝐼𝑐 and 𝐾𝐼𝑐 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.