Numerical simulation of tunnel ventilation in Jiaoxihe tunnel, China

摘要

Ventilation problems in tunnel construction are increasingly evident, but the methods used to estimate the ventilation time in simulations of construction schedules are currently all empirical. In this study, the wind speed produced during forced ventilation was simulated using a three-dimensional renormalisation group k-e turbulence model in computational fluid dynamics software. Time-dependent variations in the flow and concentration fields during the construction schedules were also determined using simulations. The results showed that the airflow close to the vortex near the working face and branch tunnel was complex but stabilised gradually with increasing distance from this area. The release of harmful gas produced after blasting was characterised by two types of discharge, namely movement and diffusion. Movement pertains to the exit of harmful gas from the tunnel through the working face, whereas diffusion refers to the dispersal of the gas as it moves; finally, the gas discharges outside through the branch tunnel. The flow and concentration fields of the main and branch tunnels were analysed. Certain suggestions and comments are offered. The best entry period for construction workers was determined based on the permissible carbon monoxide concentrations, providing a theoretical basis for construction workers to ensure reasonable construction progress.

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