Advanced velocity modeling and imaging of rock mass in hydraulic tunnels with high efficiency and accuracy

The accurate calculation of the P-wave velocity information of the rock mass in front of the tunnel face and the accurate imaging of the adverse geological structures are the key to improve the accuracy of the advanced geological prediction of tunnels with seismic waves. The full-waveform inversion (FWI) in time domain can realize high-precision modeling for longitudinal wave velocity of rock mass in front of the hydraulic tunnel. Considering the cross correlation misfit function, the influences of energy unevenness among different boreholes on the inversion results can be solved, and the noise resistance of inversion is improved. A multi-source coding strategy for seismic data of hydraulic tunnels is proposed to improve the efficiency of FWI calculation. The reverse time migration (RTM) based on the bidirectional illumination compensated cross-correlation imaging conditions is performed to accurately image the adverse geological structures based on the velocity model provided by FWI. The numerical tests of a variety of geological models for tunnels verify the effectiveness of the advanced velocity modeling and imaging of rock mass in hydraulic tunnels with high efficiency and accuracy, and it may provide a theoretical basis for practical tunnel engineering.