In order to provide effective guidance to the construction and to ensure the safety of workers

numerical simulations were performed on distributions of airflow

temperature fields

oxygen content

and carbon dioxide content during the process of mechanical ventilation using the CFD software. The results demonstrated that

in the course of mechanical ventilation

compared with the pipe trench

the recovery of environmental condition such as temperature and gas volume fraction including oxygen and carbon dioxide were more rapid in the heat chamber. The air flow was mainly along the bottom of the pipe trench and the air velocity at the top of the pipe trench was small because of the internal structure and thermal lift in the pipe trench. For the pipe aforementioned

when the ventilation volume was 6 000

8 000

10 000

12 000

14 000 m3·h-1

the minimum ventilation time needed should not be less than45

32

22

15

10 minutes

respectively. In practical operation

oxygen content at the top of the central part of the trench should be regarded as the key parameter to evaluate the ventilation effects