Abstract: In order to study the accumulation of gas near the fire door and the mezzanine of tunnel when gas leaks in the utility tunnel, an experimental study was carried out on the model test bench with neon gas instead of gas. Numerical simulations were also used to verify the feasibility of neon gas instead of gas. It is proposed to add fire-proof air outlets at the highest point of the utility tunnel firewall and to install inducing fans on the mezzanine of tunnel. And the improvement effect of gas accumulation under this method was simulated. The results show that when the leak is located on the upstream side of the fire door, gas accumulation occurs in the upper part of the upstream and downstream near the fire door. The increase in the diameter of the leak aggravates the accumulation of gas. The higher the gas pipeline pressure is, the higher the gas leakage concentration and diffusion fluctuation is. Gas accumulation also forms at the dead corners of the utility tunnel mezzanine. The addition of fire-proof air outlets above the fire door and inducing fans in the mezzanine of the utility tunnel can effectively reduce the gas accumulation near the fire door and in the interlayer.

Key words: utility tunnel; gas leakage; accumulation; model experiment; simulation