Research on the Application of HHT Time-Frequency Analysis Method in Damage Analysis of Integrated Pipe Gallery

The comprehensive utility tunnel plays a crucial role in the urban development process. However, the integration of energy pipelines into the comprehensive utility tunnel can introduce a range of safety concerns. Therefore, researching the damage characteristics of urban comprehensive utility tunnels under internal gas explosions is of significant importance for optimizing tunnel design. The study involves designing and conducting explosion similarity model experiments in comprehensive utility tunnels. Through the use of piezoelectric smart aggregate monitoring technology, the tunnel model's damage is monitored. This research aims to analyze the damage and destruction caused to the tunnel structure by internal gas explosions. It will provide a basis for determining the characteristics of tunnel damage. This paper first employs a combination of Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) and an improved wavelet threshold method to denoise the monitoring signals. Next, it compares the signal strength peaks before and after the explosion to conduct an initial analysis of the tunnel's damage situation. Finally, through Hilbert-Huang Transform (HHT) transformation, comparisons were made between the energy and frequency distribution of signals from 'RT5-Black5' and 'RT6-Black7' before and after two explosions, further elucidating the damage characteristics of the tunnel. Upon analysis and verification, the combination of CEEMDAN and the improved wavelet thresholding method demonstrates superior denoising effects, it is confirmed that the accumulated energy decreases and the frequency band widens after the explosion.