## 6 Conclusions  
This paper proposed a new technology for construction ventilation in large-scale underground oil storage caverns using the shafts as the fresh air inlet. The RNG \(k\)-\(\varepsilon\) turbulence model was firstly validated with the field test values, and it was found that the simulated results agreed well with the test results. Then, the distribution of air velocity and the CO concentration in the forced ventilation scheme and axial-flow gallery ventilation scheme were investigated. The main results are as follows:  
1. The construction of large underground caverns usually adopts layered excavation, and the forced ventilation method is mostly applied in the upper layer construction. Due to the restriction of the construction roadway size and the clearance requirements for transportation, the duct diameter and air volume cannot be increased Consequently, the ventilation quality cannot meet the requirements of the cavern environment. Because the ventilation distance exceeds 1500 m, the stable air velocity in the cavern is only 0.15 m/s, which is below the minimum air velocity requirement of the relevant standards. In addition, there is a very complicated eddy zone in the area of about 20 m from the heading face.
2. The axial-flow gallery ventilation scheme is carried out when the excavation of the cavern upper layer is completed and connected with the shaft. The scheme utilizes the shafts as the fresh air inlet and the construction roadway as the polluted air outlet to create the gallery ventilation. It can ensure that the direction of the airflow is the same as that of heavy trucks, fresh air is always near the excavation face, and the disturbance of the process is greatly reduced. It reduces energy consumption and has good prospects for popularization and application.
3. There is no need to set up the air duct in the axial-flow gallery ventilation scheme, which greatly facilitates the cavern construction and avoids duct damage caused by blasting. The scheme is suitable for the large-scale caverns with a ventilation distance less than 2 km, each channel is effectively used, and the intermediate construction shaft is not needed. If the ventilation distance exceeds than 2 km, it is possible to use jet fans to assist the axial flow gallery ventilation mode or to completely adopt jet-flow gallery ventilation.
4. The power of the axial fan and the jet fan should be no less than 135 kW and 75 kW, respectively. The jet fan should be arranged at the airflow steering place. The axial fan placed at the top and bottom of the shaft has little impact on the field ventilation effect, so the position can be selected independently according to the convenience of the fan installation.  
Figure 14: (a) CO concentration in monitoring section with ventilation time; (b) CO concentration distribution at the breathing height.  
**Author Contributions:** [PERSON] analyzed of calculation results and wrote the article; [PERSON] carried out the numerical simulation; [PERSON] collected the data; [PERSON] offered useful suggestions for the preparation and writing the paper; and [PERSON] provided the information of construction site.  
**Funding:** This research received no external funding.  
**Acknowledgments:** The study is supported by the National Natural Science Foundation of China (NSFC) under Grant No. 51508477 and the Fundamental Research Funds for the Central Universities (Grant No. 2682016 CX012). The authors also would like to thank the anonymous reviewers and handling editors for their constructive comments.  
**Conflicts of Interest:** The authors declare no conflict of interest.