Investigating the diffusion of pollutants and the variation law of temperature field in blasting construction of large energy storage cavern groups in extremely cold region

This study employs CFD to establish a three-dimensional model of a construction tunnel for large-scale underground energy storage in extremely cold regions. The model simulates the coupled distribution of flow, temperature and pollutant fields, with subsequent validation. It further investigates airflow patterns and CO migration under different ventilation modes, analysing their impact on the tunnel’s thermal environment. Results indicate that tunnel excavation in frigid climates requires simultaneous consideration of pollutant dispersion and external cold air intrusion. Under forced ventilation, pollutant discharge pathways are extended, requiring approximately 30 minutes for CO concentrations at the working face to reach safe levels, with cold air penetrating about 150 meters. Exhaust ventilation also exhibits delayed pollutant clearance; however, it isolates the main tunnel from cold air ingress. Mixed ventilation effectively removes pollutants, achieving safe CO levels in about 18 minutes, but the induced negative pressure draws cold air approximately 380 meters into the tunnel. Attention must be paid to balancing supply air volume and implementing entrance insulation measures to minimise cold air interference with the tunnel temperature field.