Acoustic parameters and wave velocity field evolution characteristics in the high-stress region of granite

Abstract

The risks of underground engineering originate from disturbances caused by the alterations to the stress field within rock masses. To understand the variations in the stress field within rock masses under local stress conditions, a set of double-hole pullout tests was used to design. The MS/AE location and tomography were used to investigate the evolution characteristics of the internal stress concentration area in granite. Results show that acoustic emission events transition from scattered and nucleated to regionally aggregated, then developing into arc-shaped patterns, ultimately exhibiting a trend of semi-spherical distribution. The increase in the fractal dimension of the spatial distribution of acoustic emission events indicates increased stress concentration degree, whereas a decrease signifies dispersion or transfer. Tomography results demonstrate the dynamic development process of local stress zones, with initial velocity anomalies as the core, continuously aggregating and expanding, showing an increasing difference trend compared to the velocity outside the region.