A full-scale experimental investigation of natural gas explosion in a 710-m long utility tunnel with multiple pipelines

Abstract

Natural gas poses significant risks to the safe operation of utility tunnels, which house multiple critical infrastructure systems, including natural gas pipelines. To date, no full-scale gas explosion tests in utility tunnels have been published, and there is ongoing debate about whether pipelines can withstand such explosions. This study presents the first-ever 1:1-scale experiments conducted in a 710-meter-long tunnel with cross-sectional dimensions of 3.2 m × 2.6 m. Three pipelines, each approximately 25 m in length and constructed to industrial standards, were used to investigate potential damage. The experiments comprehensively captured the development of flow fields, including flame images, flame signals, temperature, and overpressure, as well as pipeline responses. Results revealed that variations in overpressure within the combustion region were driven by both positive and negative feedback loops. A significant pressure drop was also observed as airflow passed through a local expansion. The experiments further demonstrated that while pipelines within utility tunnels are unlikely to be directly damaged by gas explosions, accessories such as racks are at high risk of severe destruction. These findings offer essential insights for improving the safety design, construct, and operation of tunnel-like spaces involving flammable gases.