Environmental Measurements of Air at Underground Space

摘要

Measurements of environment were carried out at a shallow underground quarry space with internal volume of 14600 m3.It was difficult to measure the ventilation airflow with usual method on flow quantity provided from inlet partal,because the space volume was too large and the flow was unsteady.In present study,the tracer gas method was applied to evaluate effective ventilation airflow rate in the space.A photo-acoustic gas monitor,that has high sensitivity of 10ppb resolution of SF6 gas used for the tracer gas,was set in the space to measure air exchange rate from the gas concentration-time decay curves.The seasonal variations of airflow and thermal environment in the space were investigated by 13 times of measurements during a year.Rock dust concentrations in internal air were also measured at the same time in the space.The correlations between effective ventilation airflow rate,thermal environment in the space and dust concentrations were analyzed and discussed based on present measurements data during a year.It has been concluded that the reason of seasonal variations of effective ventilation flow and dust concentration is mainly difference between air temperature affected by rock surface in the space and outer atmosphere air temperature.Especially in summertime,it generated lower natural ventilation flow and higher dust concentration that internal air with lower temperature was stable due to its larger density compared to outside high temperature air.