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| wind speed at air duct outlet V (m/s) | average wind speed near the tunneling face V̅ (m/s) | CO average concentration (mg/m3) |
|---|---|---|
| 6 | 0.83 | 67.42 |
| 10 | 2.12 | 58.64 |
| 14 | 3.67 | 49.38 |
