Completed gas drainage technology with downward borehole for high outburst seam opening in deep mine

In order to solve the gas abnormal problem occurred when air retuning gateway in No. 2 Level of-943- -1 000 m North Wing of Guqiao Mine and deep air in take shaft passed through No.6 seam,according to the soft seam,low permeability,high geostress,high gas pressure and high gas content features of the deep mine,the do wnward passed through strata borehole was provided for the construction of the roof gateway,including the cutting,full length casing drilling,rapid borehole sealing and othe r techniques and were applied to the site practices. The results showed that the downward boreholes in No. 6 seam of the air retuning gateway had drainaged gas of 172 0 00 m3 and the pre-drainage rate in the seam opening area was 45. 3%. An in-situ gas pressure of the seam opening area was 5. 18 MPa,the residual gas pressure was 0. 22 MPa,the in- situ gas content was 10. 24 m3/ t,the residual gas content was 5. 06 m3/ t. Neither the residual gas pressure nor the gas content was over the critical value of the state and the mining area. The technology was also successully applied to open No. 6 seam in a deep mine air intake shaft,the construction period was highly reduc ed and the safety and high efficient seam opening in high outburst seam in deep mine was realized.