Estimation of mode I fracture toughness of rock and its impact factors analysis

The relationship between mode I fracture toughness KIC and compressive strength σc of rock makes it possi- ble to estimate KIC values from σc based on empirical relationship between KIC and σc . However,the estimates are in- fluenced by the KIC test methods and lithology. In order to obtain more reasonable and accurate KIC values of rock,the authors established empirical relationships between KIC and σc under different KIC test methods and lithology based on the statistical regression of test data collected from literature,and then the authors analyzed their differences and appli- cability. Results indicated that the empirical relationships between KIC and σc obtained from the four different sugges- ted KIC test methods were all in good but obviously different linear relationship,in which the relationship obtained from cracked chevron notch Brazilian disc ( CCNBD) specimens was proposed to estimate the KIC values of rock. Mean- while,the results also showed that it was more applicable for homogeneous and isotropic rocks to estimate KIC values from empirical relationships. It should be pointed out that the estimates obtained from empirical relationships can never replace the lab tests,and the empirical relationships established by lab tests is a necessary premise for all indirect esti- mations.