Fast marching method-based bent-ray tracing for three-dimensional velocity imaging in mines

Three-dimensional (3D) seismic velocity imaging is crucial for understanding rock mass stress and structures in mining. Conventional straight-ray tomography suffers from ray-path mismatches with true wavefield propagation in complex media, leading to reduced velocity model accuracy. To address this, we propose a 3D velocity imaging method that integrates the Fast Marching Method (FMM) for bent-ray tracing with the Algebraic Reconstruction Technique (ART) for velocity inversion. The proposed approach was validated through checkerboard tests, recovery tests, and laboratory Lead-Break experiments. Results show that FMM-based ray tracing significantly improves inversion accuracy, achieving root-mean-square (RMS) travel-time residuals of 1.39 ms and 28.66 ms in recovery and field tests, corresponding to reductions of 76.6% and 18.6% compared with straight ray tracing-based methods. Application in the Yongshaba mine, Guizhou Province, China, revealed a distinct low-velocity zone surrounded by high-velocity regions, which is consistent with mining activities and excavation plans. This study demonstrates that the FMM-ART framework provides a robust and accurate tool for mine-scale velocity imaging, with implications for monitoring stress evolution, improving safety, and potential integration with real-time monitoring. • FMM is applied for the travel time computation of mine-scale velocity inversion. • FMM-based bent-ray tracing outperforms traditional straight-ray methods, validated by synthetic, field, and laboratory tests. • A low-velocity zone surrounded by high-velocity anomalies was identified in the Yongshaba mine, consistent with mining activities.