Strong interference suppression and hidden crack detection using a collaborative EEHR-RTM and A-FKM framework

Abstract Achieving high-precision imaging of hidden cracks in tunnel linings is challenging due to strong interference from rebar clutter. To address this issue, we propose a collaborative imaging method that integrates Edge-Enhanced High-Resolution Reverse Time Migration (EEHR-RTM) with Adaptive Frequency-Wavenumber Migration (A-FKM). The EEHR-RTM method accurately reconstructs the geometric contours of both rebars and cracks, while the A-FKM framework effectively suppresses strong rebar interference signals and preserves the amplitude of defect reflections. Validation through FDTD simulations and laboratory model tests demonstrates that, compared to conventional RTM, the proposed method significantly improves key quantitative metrics: the Signal-to-Noise Ratio increases from 5.40 dB to 29.58 dB, the Gradient Energy increases from 2.417×10⁹ to 1.110×10¹⁸, and the Edge Density increases from 0.004 to 0.027. Furthermore, compared to traditional F-K migration, LRSD, and SVD, the proposed method achieves a maximum rebar clutter removal rate of up to 87.9%. This approach enables high-definition imaging of millimeter-scale cracks even under strong rebar interference, providing a reliable technical pathway for the nondestructive testing of hidden defects in tunnel linings.