Tunnel Advanced Detection Method Based on Observation System Optimization and Angle-Domain Reverse Time Migration

Due to space constraints in the narrow tunnel, it is difficult to arrange the seismic acquisition and observation system. This makes the advanced detection imaging results prone to artifacts and false images, which reduce the detection accuracy of unfavorable geological bodies. Therefore, by establishing a typical tunnel geological model and adopting the reverse time migration (RTM) imaging method, analyze the influence of different observation system arrangements on the imaging accuracy of tunnel advanced detection . A coincident source and geophone observation system layout method is proposed, geophones are arranged on the side walls on both sides near the tunnel face, and seismic sources are placed on the tunnel face and at the geophone positions, Thus improving the ability to identify geological information ahead of the face. To address the issues of low-wavenumber noise interference and insufficient imaging of steeply dipping structures in tunnel RTM, proposed an angle-domain reverse time migration method based on the Poynting vector. This method decomposed seismic wavefields by angle to suppress noise and enhance the imaging accuracy of advanced detection. The study indicates that the proposing coincident source and geophone observation system and angle-domain imaging method effectively reduce imaging interference and improve imaging precision.