Identification of precursor for fracture failure of brittle rocks based on digital image correlation technique

Understanding the failure mechanism and process of rock is of great significance for in-depth study of rock failure precursors and prevention of potential rock engineering instability. Numerical compressions on intact rock and excavated rocks were carried out and the digital image correlation (DIC) technique was used to measure the full-field displacement and strains to study the precursor of rock fracture. The ratio of shear strain to loading time and absolute standard deviation of shear strain field were proposed. The reliability of the DIC algorithm in studying the rock deformation and failure was verified by comparing with the numerical simulation. The results show that the sudden change of shear strain is closely related to the occurrence of internal cracks in rocks during the loading process. The shear strain of certain tracing points near the failure region as well as the value of shear strain filed has good correlations with the rock fracture failure. The shear strains, shear strain-time ratio, and shear strain field of coal specimen under experimental compression were discussed. The feasibility of the shear strain of the rock specimens in predicting the fracture failure was verified. This study, through the introduction of novel quantitative indicators and the adoption of anintegrated numerical-experimental validation strategy, systematically demonstrates that theanalysis of the shear strain field based on Digital lmage Correlation (DlC) technology can serve asan effective and reliable method for identifying precursors to rock fracture. This finding not onlydeepens the understanding of rock failure mechanisms but, more importantly, provides atechnically practical framework for predicting and preventing instability failures in geotechnicalengineering practice. • Full-field displacement and strains are proposed to study the precursor of rock fracture. • Failure precursor indices derived from strain field were applied and verified. • A reference for identifying precursor of rocks based on DIC is provided.