Experimental and numerical investigation of gas diffusion under an urban underground construction

Abstract

• Built 10 m full-scaled utility tunnel mockup for experimental research. • Evaluated different air supply diffuser models and turbulence models. • Qualitative and quantitative comparisons for model performances. Rapid increase of urban underground constructions has a great consideration of underground environment safety and how to expel toxic gasses out of tunnels effectively. The utility tunnel is a typical urban tunnel construction with multiple underground pipelines including gas pipelines, and it is necessary to investigate characteristic of gas diffusion and monitor gas leakage to ensure tunnel safety. In this study, the experimental measurements of airflow and gas distributions were conducted in a 10 m full-scaled utility tunnel mockup, and gas diffusion characteristic was also investigated. Numerical simulation of utility tunnel leakage was also conducted by computational fluid dynamics (CFD). Different turbulence models and different air supply diffuser models were compared via the experimental results based on visualization and the relative root-mean-square error (RRMSE) index, which quantitated the difference between the numerical and experimental results. The results showed that the standard k − ε turbulence model and random air opening model could provide better results than other models. According to the experimental data analysis, it was necessary to consider the optimization of monitoring detector arrangements in actual utility tunnels. This study provided basic experimental data and the validated numerical model for the leakage source identification and underground tunnels simulation research.