Study on Pressure Released Gas Drainage Technology in Flat and Contiguous Seam Groups with Soft Seam, Soft Roof and Soft Floor

In order to improve gas drainage effect of flat and contiguous seam groups with soft seam, soft roof and soft floor in plateau mountain area, taking No. 1 805 Coal Mining Face in Xiaoyaogou Mine as a study subject, the resources division prediction method was applied to predict the gas emission quantity of coal mining f ace. And the effective gas drainage method was determined according to different gas resources. Based on a pressure released gas drainage theory and seam gas res ource division control idea, a comprehensive gas drainage method combined with pre- drainage and pressure released gas drainage was provided before mining, the mi ning and after mining in multi adjacent seams of flat and contiguous seam groups with soft seam, soft roof and soft floor. The results showed that during mining period 0 f upper protective seam in the flat and contiguous seam groups with soft seam, soft roof and soft floor, the pressure released gas in protected seam would be natural di scharging mainly and the goaf gas drainage would be the key in the protective seam coal mining face. After the comprehensive gas drainage measures conducted, duri ng mining process, the gas content in the air retuning gateway and the upper corner of the protective seam coal mining face was reduced from 1. 7% to 0.5%~ 0.6%, t he gas drainage volume reached to 900 500 m3, an average gas drainage rate was improved from 39.5% to 63. 59%, after mining in C8 seam, the gas pressure in C9 seam was reduced from 0.95 MPa to 0. 18 MPa, the gas content was reduced from 12.51 m3/ tto2.91 m3/ t and the outburst danger of C9 seam in the protection SCo pe was eliminated.