Effects of test procedures and lithology on estimating the mode I fracture toughness of rocks using empirical relations

Abstract

AbstractEmpirical estimation is a common method for getting mode I fracture toughness KIC of rock. By collecting data from tests in this study and literature, 204 sets of KIC and tensile strength σt test data are obtained for new empirical KIC‐σt relations regression. The empirical relations make the estimation of KIC values from σt conveniently, but test procedures and lithology will influence its reasonability and reliability. Results indicate that the empirical KIC‐σt relations obtained from the four different suggested KIC test methods are all in good but obviously different linear relationship. The analyses show that cracked chevron notch Brazilian disc specimen (CCNBD) test‐based empirical relation is more accurate for estimating KIC than the other three test‐based empirical relations. As to different lithology, isotropic rocks such as sandstone and carbonatite may be more appropriate for the application of empirical estimation method. However, for coarse grained or anisotropic rocks such as granite and marble, estimation method should be applied carefully because of possibly weak KIC‐σt relations.