Statistical fracture toughness analysis of Guiting limestone using disc shape test specimens

摘要

Disc specimens such as the centre cracked Brazilian disc (BD) subjected to diametral compression and the edge cracked semi circular bend (SCB) samples under three point bend loading are among the most commonly used test samples for conducting fracture toughness tests on rock materials. In this research, the mode I fracture toughness of a sedimentary soft rock (Guiting Limestone) was investigated statistically by means of both BD and SCB specimens. For each specimen, a total of 15 fracture tests were conducted. Geometrical parameters such as specimen thickness, radius and crack length were the same for both sets of samples. The results show that there was a significant difference between two sets of test data. The average K_(Ic) value for BD and SCB specimens was found to be 0.24 and 0.33 MPa m~(0.5), respectively. The difference in fracture loads between the two different disc specimens was found to be related to negative T-stress.