Airblast waves and noises induced by tunnel delay blasting: Field measurement and tempo-spatial analysis

Residents living near drill-and-blast tunnels often experience disturbances from blasting operations. This motivates us to investigate the characteristics of airblasts and resulting noise through on-site monitoring at three tunnels. The research focuses on both the temporal evolution and spatial propagation of airblasts. Temporal analysis, including peak overpressure (POp), positive duration (PD), and Fourier main frequency (MF), emphasizes the relationship between airblast characteristics, blasting delays, and rock grade. It shows that airblast bandwidths are typically in the range of 3–200 Hz, with noise levels exceeding 130 dB, which is comparable to jet engines and rocket launch. Spatial propagation analysis reveals the impact of tunnel space on airblast propagation. Although POp and PD typically decrease with distance inside the tunnel, wave superposition can cause increased overpressure and prolonged durations at far-field distances (above 60 m kg −1/3 ). Outside the tunnel, sound radiation was influenced by azimuth and was basically determined by sound power — an often-overlooked factor. To address the anisotropic propagation of airblasts, a predictive model was proposed for external noise levels, considering variables like distance, azimuth angle, initial sound power, and wave expansion. Validated by tests, this model successfully unifies data from three studies, helping to explain and predict airblast disturbances near tunnels.