On the western plateau of China, ventilation problems brought on by low atmospheric pressure must be overcome. And CO migration after blasting in high-altitude tunnel by inclined shaft has become a significant scientific issue. In this study, the Computational Fluid Dynamics (CFD) method was used to analyze the flow field characteristics at the junction of the inclined shaft and tunnel. In addition, the effects of different fan opening modes and different initial CO concentration distributions on the ventilation were discussed. The simulation results showed that the main difference in the ventilation wind field was reflected in the position of the vortex region due to the different fan opening modes. Meanwhile, various initial CO concentration distributions showed different migration when there was no air volume difference between the left and right tunnels. Eliminating vortex zones and fully using high velocity airflow could improve relative ventilation efficiency by at least 18%. CO would accumulate in the opposite direction of the tunnel if only one of the fans was turned on. Therefore, a two-stage ventilation scheme was proposed, and the energy consumption was reduced by at least 33%. This research can provide guidance on high-altitude tunnel construction with multiple working faces to improve ventilation efficiency and reduce energy consumption.
With the excavation of a metro station in a confined water-rich stratum as our background, the sensitivity of four typical recharge parameters is analyzed by using numerical simulation. Based on the orthogonal analysis method, an optimal recharge scheme was obtained. The results show that the main influential factors of ground settlement and groundwater recovery are recharge pressure and recharge depth. The main influential factor of retaining structure deformation and influence radius of recharge is the distance between the recharge wells and the foundation pit. For the groundwater recharging of a deep excavation in the water-rich confined area of Jinan, China, the optimal effect can be achieved when setting recharge wells with a depth of 50 m arranged in a line with a spacing of 10 m at a horizontal distance of 20 m away from the retaining wall and recharge pressure is 40 kPa. With the same construction difficulty, the maximum settlement in optimized scheme decreased 71.19%, the flux of groundwater recovery increased 11.96%, the maximum horizontal displacement of the wall decreased 15.61%, and the influence radius of recharge enlarged 8.62% compared to original scheme.
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