Influence of Fissure Inclination on Deformation and Strain Distribution of Damaged Materials Based on Digital Image Correlation Method

Abstract

Sandstone-like specimens with fissures (fissure inclination 0°, 30°, 45°, 60°, 75°, 90°) were made for investigation into the influence of fissure inclination on deformation of damaged rock mass. The high-speed camera was used to record the deformation images of the specimen. Based on the digital image correlation (DIC) method, the strain distribution was calculated. The strain evolution pattern of fissured rock mass under the effect of fissures was analyzed via the maximum equivalent strain, average equivalent strain, and strain distribution, respectively. The results revealed that prefabricated fissure specimens exhibit four distinct phases: stable deformation, accelerated deformation, crack propagation and specimen failure. The DIC analysis revealed that the new cracks on the fissured specimens predominantly originate from the fissures' tips and propagate in a direction aligned with the principal stress. The maximum equivalent strain of the specimen was related to the fissure inclination. The maximum equivalent strain of the specimen with a fissure inclination of 90° and the intact specimen increased linearly. For fissure inclination between 0° and 75°, the strain of the specimen exhibited a pronounced increase following the accelerated deformation stage. The average equivalent strain of the specimen initially rose and then declined with the increase of the fissure inclination. The maximum value of the average equivalent strain was observed when the fissure was inclined approximately up to 45°.