Abstract
In this paper described are the test results on specimen size effect as well as specimen shape effect in the fracture toughness testing of rocks according to the “Suggested Methods for Determining The Fracture Toughness of Rock” proposed by Commission on Testing Method in ISRM. Test results for three kinds of rocks show that even corrected fracture toughness is not independent of specimen diameter, and that there exists a unique relation between corrected fracture toughness and crack extension. That is, both size and shape effects are caused by the difference in crack extension at which fracture toughness is evaluated.
