Abstract: To address the insufficient understanding of how bent structures in urban utility tunnels influence gas explosion propagation and structural response, an experimental study was conducted on the propagation and structural response characteristics of gas explosions in utility tunnels under different bend angles. An integrated monitoring approach is employed that combines unmanned aerial vehicle image acquisition, pressure measurements, and half-bridge strain and strain matrixes, enabling multi-dimensional and synchronous observation of flame propagation, overpressure distribution, and dynamic strain responses in both the overall structure and the specific bend regions. The results reveal the following: (1) Increasing bend angle significantly suppresses flame propagation, with the maximum flame travel distance decreasing from 0.730 m in straight tunnel conditions to 0.636 m at a 90° bend, and results in earlier occurrences of flame evolution stages. (2) Although the bent structure reduces the overall peak overpressure, it intensifies local pressure oscillations; as the bend angle increases, pressure fluctuations in the bending area become more pronounced, accompanied by heightened turbulence effects and stress concentration. (3) The structural deformation exhibits a sequential pattern, initially dominated by circumferential expansion, followed by axial stretching. Moreover, the degree of this directional transformation diminishes with increasing bend angles, with reductions of 25.4% and 28.9% observed for the 60° and 90° conditions, respectively, compared with the 30° condition.

Key words: gas explosion, urban utility tunnel, bent structure, flame propagation, explosion overpressure, dynamic strain response