Numerical simulation study on ventilation and harmful gas diffusion during the construction period of shafts

In the process of excavating the shaft, blasting will generate a large amount of CO, which will pollute the environment inside the shaft and jeopardize the health of the construction workers. In this study, the theoretical equation of CO distribution inside the shaft during the construction period is derived based on the diluted ventilation model. The ventilation process in the shaft under different working conditions was numerically simulated. And the grid convergence index method was used to study the independence of the grid to ensure the accuracy of the numerical simulation. The selection of the location of the duct is the main factor affecting the distribution of the flow field in the shaft. The distance between the outlet of the duct and the working face of the shaft is the main factor affecting the dilution of CO in the shaft. The flow rate of the jet ejected from the outlet of the duct is the main factor influencing the movement rate of the CO peak. The distribution functions of hazardous gases in the shaft with space and time when the shaft is ventilated by forced ventilation are derived. Based on the diameter of the shaft and the ventilation volume, the formula for estimating the ventilation time required for shaft construction was constructed. The accuracy of the formula was verified by the actual projects. The optimized ventilation measures by using the results of this study can effectively improve the construction environment in the shaft, which has certain significance for similar projects.