Numerical simulations of radon exhalation from surrounding rocks of single and double underground roadways.

The radon exhalation rate of surrounding rocks in underground roadways is an important parameter in determining radon exhalation capacity and ventilation flowrate for radon removal. By approximating the roadways as thick-walled, porous cylinders, this study investigates radon exhalation from their surrounding rocks via simulations using computational fluid dynamics (CFD). Radon exhalation rates of single and double underground roadways were computed and analysed under different pressure differences, radon diffusion coefficients, permeabilities of rocks, single roadway locations and additional parallel roadway orientation. The radon regulating zone was presented and the effect of pressure difference on it was analysed. By fitting the data from simulation results, an estimation model was obtained for the radon exhalation rate of a single roadway. For two adjacent parallel roadways with a distance greater than or equal to 50m, the model is also suitable for estimating the radon exhalation rate when the rock permeability is less than 1 × 10-14 m2 and the ratio of permeability to diffusion coefficient is less than 5 × 10-9.

Optimization of the operating parameters for radon reduction on brattice induced cavern ventilation using CFD.

Cavern is a place where workers often work in underground spaces, where radon is constantly released from surrounding rock surfaces. It is of great significance to develop effective ventilation to reduce radon in underground space for safe production and occupational health. For the purpose of controlling the radon concentration level in the cavern, the influence of upstream and downstream brattice length, upstream and downstream brattice to wall width on the volume average radon concentration and the plane average radon concentration at the height of the human respiratory zone (Z = 1.6 m) in the cavern, was studied by using the CFD (Computational fluid dynamics) method, and the operating parameters of ventilation induced by the brattice are optimized. The results show that the radon concentration in the cavern can be significantly reduced by using the brattice induced ventilation compared with no ventilation auxiliary facilities. This study provides a reference for local radon-reducing ventilation design of underground cavern.