Illumination of Damage in Intact Rocks by Ultrasonic Transmission‐Reflection and Digital Image Correlation

Abstract

AbstractLaboratory‐scale experiments on intact rocks are critical to the development of physics‐based fundamental understanding of various geophysical phenomena. In this work, the capability of ultrasonic wave transmission (T‐mode) and reflection (R‐mode) to monitor damage progression in uniaxially loaded prismatic intact rock specimens has been analyzed, as it is imperative to study the observations and document the capabilities of these techniques in a controlled environment. This study is novel in the sense that the R‐mode linear ultrasonic testing (LUT) has been rarely employed in studying intact rock damage processes in a laboratory setting, with most of the studies utilizing a direct transmission (T‐mode) approach or focusing on macroscopically fractured material. The two‐dimensional digital image correlation (2‐D DIC) full‐field strain measurement approach was also used in‐sync with the LUT monitoring to explicitly correlate the stress‐induced damage in the specimens with the changes observed in the ultrasonic (T‐mode and R‐mode) signals. The results show that both the T‐mode and R‐mode LUT approaches are sensitive to detect the evolution of tensile and shear damage in the specimens, with the R‐mode ultrasonic signals showing higher degree of sensitivity to the damage in the rocks, immediately following the initiation of damage in the rock volume.