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. 2022 Jul 25;7(31):27135-27148.
doi: 10.1021/acsomega.2c01397. eCollection 2022 Aug 9.

Study of the Diffusion Law of Harmful Gases in Tunnel Construction on Plateaus and Optimization of Ventilation Parameters

Jie Liu  1 , Haowen Zhou  1 , Wanqing Wang  2 , Xinyue Hu  1 , Qian Ma  1 , Feng Lu  1
Affiliations

Study of the Diffusion Law of Harmful Gases in Tunnel Construction on Plateaus and Optimization of Ventilation Parameters

Jie Liu et al. ACS Omega. .

Abstract

To explore the diffusion law of harmful gases near the excavation face in tunnel construction on plateaus, select the optimal ventilation parameters, and improve the ventilation efficiency, Ansys Fluent was used to set the environmental parameters according to the highland, where the tunnel is located, and simulate and curve fit the diffusion phenomenon of CO and NO2 based on the fluid control equations and species transport model. The effects of air velocity, ventilation time, and duct position on the diffusion law of harmful gases were analyzed, from which the optimal ventilation conditions were selected, and the ventilation effects under the optimal conditions were compared with those under the original conditions. The study shows that after the fresh airflow passes through the outlet, part of it flows out along the tunnel wall toward the cave entrance, and the other part interacts with the return air to form a vortex; when the air supply speed is 10 m/s and the distance from the duct outlet to the excavation face is 25 m, the maximum concentration of harmful gases decreases by 92-99% after 20 min of ventilation compared with that before optimization and the smoke exhaust efficiency increases by 2.5% per minute.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Geometrical model.
Figure 2
Figure 2
Grid partitioning.
Figure 3
Figure 3
Air speed distribution near the excavation face (A, jet zone; B, vortex zone; C, reflux zone).
Figure 4
Figure 4
Streamline of airflow near the excavation face.
Figure 5
Figure 5
Concentration distribution of harmful gases at different wind speeds after ventilating for 1 min.
Figure 6
Figure 6
Concentration distribution of harmful gases at different wind speeds after ventilating for 20 min.
Figure 7
Figure 7
CO concentration distribution near the excavation face.
Figure 8
Figure 8
Isovelocity of airflow distribution near the excavation face.
Figure 9
Figure 9
Concentration distribution of harmful gases at different times.
Figure 10
Figure 10
Change curves of harmful gas concentration–time: (a) CO; (b) NO2.
Figure 11
Figure 11
Absolute slope values of harmful gas concentrations: (a) CO; (b) NO2.
Figure 12
Figure 12
Distribution of harmful gas concentrations at different ventilation distances.
Figure 13
Figure 13
Distributions of CO and NO2 in high concentrations: (a) areas with CO concentration higher than 30 mg/m3 and (b) areas with NO2 concentration higher than 5 mg/m3.
Figure 14
Figure 14
Comparisons of airflow streamlines.
Figure 15
Figure 15
Proportion of hazardous gas concentration area: (a) areas with CO concentration higher than 30 mg/m3 and (b) areas with NO2 concentration higher than 5 mg/m3.
Figure 16
Figure 16
Fitting curves of hazardous gas concentration.
Figure 17
Figure 17
Comparison of CO discharge effect near the excavation face.
Figure 18
Figure 18
Comparison of NO2 discharge effect near the excavation face.
See this image and copyright information in PMC

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