CFD simulations and control of radon migration in tunnels with fracture-pore covered layers

In underground engineering, a covered layer is usually established to provide certain support and protection for underground tunnels. At the same time, the covered layer can also inhibit radon exhalation from surrounding rock. To study radon exhalation in the covered layer and surrounding rock of a tunnel, and to control radon migration in tunnels with fracture-pore covered layers, a specific underground tunnel was chosen for analysis. A radon migration and dynamics model in the fracture-pore medium was developed, and computational fluid dynamics (CFD) simulations were performed to analyze the radon exhalation from the covered layer and surrounding rock. The impact of factors like pressure difference, diffusion coefficient, and permeability on the radon exhalation rate was examined. The results indicated that adjusting these parameters could effectively manage the radon exhalation rate, with a particular focus on the proposed active depressurization (AD) method, which can significantly reduce the radon exhalation rate and provide scientific basis for radon pollution control in underground engineering.