Experimental study on real-time monitoring of surrounding rock 3D wave velocity structure and failure zone in deep tunnels

An innovative real-time monitoring method for surrounding rock damage based on microseismic time-lapse double-difference tomography is proposed for delayed dynamic damage identification and insufficient detection of adverse geological conditions in deep-buried tunnel construction. The installation techniques for microseismic sensors were optimized by mounting sensors at bolt ends which significantly improves signal-to-noise ratio (SNR) and anti-interference capability compared to conventional borehole placement. Subsequently, a 3D wave velocity evolution model that incorporates construction-induced disturbances was established, enabling the first visualization of spatiotemporal variations in surrounding rock wave velocity. It finds significant wave velocity reduction near the tunnel face, with roof and floor damage zones extending 40–50 m; wave velocities approaching undisturbed levels at 15 m ahead of the working face and on the laterally undisturbed side; pronounced spatial asymmetry in wave velocity distribution—values on the left side exceed those on the right, with a clear stress concentration or transition zone located 10–15 m; and systematically lower velocities behind the face than in front, indicating asymmetric rock damage development. These results provide essential theoretical support and practical guidance for optimizing dynamic construction strategies, enabling real-time adjustment of support parameters, and establishing safety early warning systems in deep-buried tunnel engineering.