An Experimental and Numerical Study on the Effect of Loading Type and Specimen Geometry on Mode-I Fracture Toughness of Rock

As fracture toughness (KIC) is one of the most practical parameters in fracture mechanics of rock, this article aims to investigate this parameter both experimentally and numerically. In the current research, mode-I fracture toughness of a kind of limestone was investigated by performing Brazilian disc, cylinder direct tension and under bending cubs. Through performing some tests on straight notched Brazilian disc specimen (SNBD), the effect of specimen diameter and crack length on the rock mode-I fracture toughness was investigated. Moreover, in order to determine the effect of the loading type on the mode I fracture toughness; two other tests were conducted on the cylinder direct tension specimens and cubic specimens (DT and SENB). Then, the effect of the crack length and the specimen diameter on the rocks mode-I fracture toughness was investigated through conducting the statistical analysis of variance (ANOVA) on the results obtained in DT and SNBD tests. In order to determine the required parameters of DT and SNBD specimens for fracture toughness, finite-element software was used. The results showed that by increasing the diameter from 75 mm to 95 mm, for Brazilian disc specimens the average fracture toughness increases by 30%. Also it seems that factors such as the test and loading type as well as the crack geometry can affect the fracture roughness parameter.