A method for quantitatively evaluating the anchoring quality of resin bolts based on the attenuation coefficient of ultrasonic guided waves

• A guided wave evaluation method based on the attenuation coefficient is proposed, effectively eliminating the dependence on anchoring length in traditional amplitude methods. • Numerical simulations and experiments verify a significant positive correlation between the attenuation coefficient and anchorage density, supporting its use as a quantitative indicator of anchoring quality. • Under the same defect volume ratio, the attenuation coefficient increases as the number of defects increases. To address the challenges of multi-interface coupling and signal attenuation commonly encountered in threaded steel resin bolts operating within complex underground environments, this study proposes a quantitative anchoring-quality evaluation method based on the attenuation coefficient of ultrasonic guided waves. A three-layer cylindrical model comprising bolt–resin–surrounding rock is established, and dispersion-curve analysis is employed to investigate the low-frequency single-mode propagation characteristics of the L(0,1) mode, from which 50 kHz is identified as the excitation frequency. Finite element simulations indicate that when the surrounding rock thickness exceeds 150 mm, boundary-reflection interference can be effectively eliminated. Subsequently, indoor experiments are carried out under different anchoring densities and defect conditions. By utilizing the EMD-PCA technique to suppress signal aliasing, the attenuation coefficient of guided waves is calculated. The results reveal a significant positive correlation between the attenuation coefficient and anchorage density, with fitting correlation coefficients of 0.986 for experiments and 0.962 for numerical simulations. Moreover, the attenuation coefficient exhibits marked sensitivity to defect volume ratio and defect quantity. The proposed method enables quantitative detection of the anchoring quality of resin bolts and provides a reliable nondestructive basis for safety evaluation of mine support structures.