Method of rock bolts parameters detection based on harmonic wavelet packet transform

For the complexity and concealment of the construction, the bolt anchoring system has great difficulty in quality detection. Due to various reasons the traditional detection methods of quality are difficult to obtain effective results. In recent years, stress wave reflection has been the main method in quality nondestructive testing of rock bolts, but the reflection signal contains noise which brings great inconvenience for the signal analysis. Harmonic wavelet has a strict "box" spectrum characteristics, and by using the harmonic wavelet packet, signal can be decomposed into different frequency bands and the unwanted ingredients can be effectively eliminated, so the denoised signal could be obtained. In this paper, a reflection signal is decomposed by using the harmonic wavelet packet, and the appropriate decomposition layers and the frequency band width are chosen, the effective frequency band is extracted and reconstructed. Compared with the classical wavelet transform, experiment results show that the bolt parameters accuracy using harmonic wavelet packet is improved.