Numerical simulation of air ventilation in super-large underground developments

• CO concentration is a key factor of construction ventilation for super-large underground developments.
• A full-scale 3D model for super-large underground space was developed.
• Diluting CO was simulated by using species transport model.
• Discharge dust was simulated by using discrete phase model.
• Minimum air velocity of 0.15 m/s meets the standard requirements for oxygen, dust and temperature, but not the CO concentration.

Recent advancements in engineering technology have enabled the construction of super-large underground engineering projects in China. Currently, the ventilation requirements and standards of normal-size underground spaces are used for super-large underground excavating engineering projects in China. For example, the minimum air velocity of 0.15 m/s is the standard velocity for normal-size underground spaces; however, this value is also used as the required air velocity for diluting underground contaminants in super-large underground developments. This paper aims to examine the minimum ventilation requirements for super-large underground developments (S > 100 m2). A three-dimensional computational domain representing a full-scale underground space has been developed. The pertinent parameters such as dust concentration, smoke density, oxygen concentration and air temperature have been simulated. The results show that at some specific underground conditions, the ventilation air velocity of 0.15 m/s is sufficient to control the dust level, provide required oxygen concentration and maintain the air temperature at acceptable levels during development; however, it is not sufficient to bring the CO concentration below an acceptable safe limit. This must be considered by the ventilation system designers of super-large underground developments.