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

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.