Investigating the effect of fractures on unusual gas emission in coal mines; case study of Parvadeh coal mine, Iran

In the present study, an investigation was carried out on Parvadeh coal mine in Tabas, Iran, to survey the effect of fractures on unusual methane gas emission in coal mines. This coal mine was chosen for investigating because of its high methane gas content in the coal body and available data from sensors in desired locations. Gas concentration monitoring programs were carried out at the mine site and a large amount of data were collected and analyzed. It is revealed that there is a good correlation between excavating fracture-bearing faces and high methane gas emission events at the mine site. High gas emissions have been observed before, during, or after excavating fracture-bearing faces. When gas content is high and all boundary conditions are met, rockbursts, faults movement and also mining activities can trigger unusual gas emission, and sometimes the gas gushes are violent enough to fit into the category of gas outbursts. Since the fracture generation is happening before the increase of gas concentration in the air, a sensitive and highly accurate microseismic monitoring system can be used to detect locations of rock fracturing, thus provide an effective means to issue warnings of high gas emission in the working area.