Journal of the Korean Society of Mineral and Energy Resources Engineers ISSN:2288-0291(Print) 2288-2790(Online) 한국자원공학회지

The rock fracture toughness, like other rock properties, generally depends on the specimen geometry and test results substantially scatter presumably due to inhomogeneity of rock materials. In this study, the mode I fracture toughness of the Pocheon granite and mortar specimens were measured using the SCB, NBD, SECRBB and CB specimens. For mortar specimens the three-point bending test, a standard test method suggested by ASTM, was also employed, and variations in the fracture toughness values measured by different specimen geometries were compared. It was found that the NBD specimen, which required much smaller specimens, produced fracture toughness values close to those measured by the CB specimen. Hence, considering inhomogeneity and anisotropy of rock materials, it would be more practical to employ NBD specimen type than the CB type, to obtain representative fracture toughness value from ample specimens.