1. Introduction
Detong Coal Mine adopts comprehensive longwall mining with sublevel caving method. During coal mining process, gas overflow may cause high gas concentration in the return air corner. Gas overrun phenomenon occurs from time to time. In order to solve the problem of gas concentration in the upper corner of the working face, and ensure mining safety, CCTEG Xi’an Research Institute helps Detong Coal Mine constructing directionally drilled horizontal gob boreholes to control gas concentration in the upper corner.
2. Solution
ZDY6000LD drilling rig and related equipment independently produced by CCTEG Xi’an Research Institute were used to construct 14 directionally drilled horizontal gob boreholes in 2105 and 2106 working faces. Boreholes were arranged in the fracture zone to reach the upper corner to achieve gas drainage purpose.
3. Construction situation
Each drilling site in the return air connecting lane of 2105 and 2106 working face is deployed. 7 Directionally drilled horizontal gob boreholes with diameter of Φ133mm are drilled in each drilling site. The target strata is the lower part of the cracked zone of the coal seam roof and the upper part of the falling arch to. The project helped achieving the purpose of gas drainage in the goaf and upper corner, and solving the problem of gas accumulation in the upper corner to the greatest extent.
4. Achieved accomplishment
In 2105 working face and 2106 working face of Detong Coal Mine, a total of 2 drilling sites and 14 horizontal gob boreholes were constructed. The final borehole diameter is φ133mm. During gas drainage process after construction, average gas concentration reaches 43%. The volume reaches 1.1m³/min, which significantly reduced the impact of gas problem during coal mining process.
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