Dynamic discrimination method of seismic damage in tunnel portal based on improved wavelet packet transform coupled with Hilbert-Huang transform

An improved wavelet packet transformation (IWPT) combined with Hilbert-Huang trans-formation (HHT) is proposed as a dynamic discrimination method (DDM) for seismic damage in tunnel portals. The similarities and differences between the method proposed in this paper and the conventional response analysis method (CRAM) are compared and analyzed by using an extensive shaking table test as the data source. To begin, a realistic wavelet basis function and decomposition order suitable for shaking table tets data are explained, a new threshold function is proposed, and noise robustness analysis are performed for the IWPT. The results reveal that the proposed damage discrimination method is accurate in determining macroscopic damage to the tunnel lining and slope when compared to conventional analysis method. The method proposed in this research also permits for the position and time orientation of damage to the slope and lining, allowing for greater understanding of the dynamic damage process.