A methane emission control strategy in the initial mining range at a spontaneous combustion-prone longwall face: A case study in coal 15, Shigang Mine, China

- Coal bed methane (CBM) needs to be controlled at spontaneous combustion-prone longwall faces.
- The main unstable CBM emissions are from the overlying strata and the initial caving of the immediate roof.
- A CBM control strategy was proposed to control CBM in the initial mining range.
- The proposed strategy has balanced the CBM control and the coal fire prevention.

:Fast drainage is a key in balancing coal bed methane (CBM) control and coal fire prevention in highly gassy and spontaneous combustion-prone longwall faces in the initial mining range. In this case study, two similar working faces, the 15202 and 15203 faces of Shigang Mine, were studied for the CBM emission history and its control strategy in the initial mining range. The field observation results from the 15202 face show that the distance of the initial mining range can be estimated to be 40 m. It was found that there was a noticeable high-concentration phase during the initial mining range in the 15202 face. This high-concentration phase is caused by the CBM desorbed from the upper-close-Coal 14 after the initial caving of the immediate roof and the subsequently relieved overlying layers. In the 15203 face, a targeted CBM control strategy was proposed to supplement the basic CBM control strategy in the initial mining range. Firstly, an additional roadway was introduced to construct in-seam boreholes in the Coal 14 before the face advancement. Secondly, fractures between upper drainage roadway and Coal 14 were enhanced by a splitting blasting. The application results show that the high-concentration phase disappeared after the application of the new CBM control strategy. It is concluded that the proposed CBM control strategy in the initial mining range is effective to control CBM emission and prevent coal spontaneous combustion in the gob at Shigang Mine. This case study provides an important engineering practice example for the CBM emission control in other CBM-rich and spontaneous combustion-prone underground coal mines.