Basic Acoustic Wave Time-Frequency Parameters of Buried Gas Pipeline Leakage

Upon leakage in underground gas pipelines, the interaction between soil particles and gas will produce acoustic events exhibiting varied frequencies, amplitudes, and energy characteristics. In order to obtain the acoustic response of gas pipeline leaks that are buried, experiments were conducted using a two-dimensional visual leak testing facility. Employing time-domain parameter analysis, fast Fourier transform (FFT), and wavelet packet analysis (WPT), this study meticulously investigated the impact of gas pressure and soil moisture on the time-frequency characteristics of the acoustic waves throughout the leakage process. The results show that: (1) the amplitude, dominant frequency, and energy of acoustic waves closely relate to the deformation and disturbance of soil morphology, (2) the amplitude of acoustic waves increases and decreases exponentially with the increase of gas pressure and soil moisture content, respectively, (3) the main frequency response of acoustic waves during the erosion process predominantly lies within the 0 to 1 kHz range, exhibiting an “N-shaped” cyclical variation, and it tends to decrease with the increase in gas pressure and increase with the rise in soil moisture content, (4) as the leakage process continues, the energy ratio of 0–156.25 Hz increases continuously, the maximum is 45.24%, and the frequency bands of 0–156.25 Hz and 156.25–312.5 Hz demonstrate a strong responsive pattern to variations in soil moisture content and gas pressure, respectively. Therefore, these two can be utilized as the characteristic frequency bands to represent the effects of moisture content and gas pressure, and (5) the leakage acoustic sources primarily originate from pipe wall vibrations, gas impact on soil particles, and friction within the soil particle medium, with the latter two types of vibrations generating more propagative acoustic waves. The research results are of great significance to the prediction of soil structure damage and the acoustic monitoring of gas leakage.