Gas explosion overpressure loads in utility tunnels under different pipe support spacing

Abstract

To investigate the effects of pipe support system characteristics on gas explosion overpressure loads in utility tunnel gas compartments, a 200 m × 2 m × 3 m model of a typical Chinese utility tunnel was constructed using CFD dynamics. Analysis of spatial and temporal distributions of explosion overpressure load under different support spacings. The results indicated that a short support spacing (L = 5 m) contributes to a more uniform distribution of the gas cloud and enhanced the average flame propagation velocity, whereas a medium support spacing (L = 15 m, 25 m) significantly increased the peak overpressure and instantaneous flame velocity. The explosion overpressure curve showed a multipeak structure, with peak P1 caused by the precursor shock wave and peaks P2–P4 caused by the reflected wave. Within 70 m, the secondary reflected wave P3 dominated, and within 130–200 m, the first reflected wave, P2, played a major role. The peak overpressure loads at different support spacings decreased and subsequently increased along the length of the utility tunnel, and the maximum peak overpressure load was reached at the end. The peak overpressure in the same cross-section is unevenly distributed; the closer to the far-end wall, the more significant the difference, and the maximum overpressure usually appears near the top of the tunnel. According to the quantitative relationship between the peak explosion overpressure and support spacing, the optimised design of the pipe support spacing should not be less than 25 m.