Full-field quantification of time-dependent and -independent deformation and fracturing of double-notch flawed rock using digital image correlation

Abstract

The quantitative characterization of time-dependent and -independent deformation and fracturing of rock is crucial to reveal the short-term and long-term instability mechanisms of structural rocks. In the present paper, we conduct uniaxial constant strain rate and stress-stepping creep tests on double-notched sandstone samples with different rock bridge and flaw inclination angles. Full-field measurements of strain and crack evolution by using digital image correlation (DIC) are presented to understand time-dependent and -independent deformation, fracturing and associated crack types and failure modes of cracked rock. Results from uniaxial and creep experiments show that the flaw inclination, rock bridge inclination and time significantly affect the evolution of the strain field, and in turn change the crack propagation behaviour, and the final strength and failure mode of the rock. The vertical maximum principal stress direction is often in compression near the flaw tips, and as it moves away from the tip, the compression gradually changes to tension, while the parallel maximum principal stress direction is often in tension. Compared with short-term loading, tensile cracks such as wing cracks and far-field cracks, are prominent under creep loading conditions and can be fully developed and characterized by a longer expanded trajectory. Highlights 1. Full-field measurements of strains and crack evolution in rock with three flaw configurations by the DIC. 2. Comparative analysis of time-dependent and -independent crack types and failure modes. 3. Tensile cracks are prominent under creep loading conditions and can be fully developed.