Application of digital image correlation and strain inversion to determine the five elastic constants of transversely isotropic rock from a single rock core by a strip load

Abstract Digital image correlation (DIC) has been widely used to measure and visualize strain fields in rocks. As an extended application, this study applies digital image correlation and strain inversion to determine the five elastic constants of transversely isotropic rock from a single rock core under a strip load. A strip load was used for making various stress conditions, and strain inversion was used to determine elastic constants by minimizing the difference between the measured and numerically modeled strain. The proposed method was validated through numerical and laboratory experiments. Numerical validations were conducted under both homogeneous and heterogeneous samples, confirming that increasing the number of strains used in strain inversion leads to more accurate results. Laboratory experiments were performed on three rock types—Onyang gneiss, Paju gneiss, and Boryeong shale—through uniaxial compression tests and strip load tests. Comparisons between DIC and strain gages in the uniaxial compression tests validated the suitability of DIC for measuring strain to determine the five elastic constants of transversely isotropic rock. In the strip load test, the range of the five elastic constants obtained from the strip load test compared well with that of the five elastic constants obtained from the conventional uniaxial compression test, confirming the validity of the proposed method. This method represents an efficient and accurate approach for applying DIC to determine the five elastic constants of transversely isotropic rock using a single rock core.