Abstract:
In order to solve the problem that the gas in contiguous seams is easy to exceed the limit, the directional long borehole extraction technology in roof is proposed. Taking 1201 working face of Wanfeng Coal Mine as an example, the influence of coal seam mining on adjacent coal seams and reasonable borehole layout position are studied by numerical simulation method and theoretical calculation method. Under the influence of coal seam mining, the upper and lower adjacent coal seams will be depressurized, resulting in gas desorption. In order to ensure the extraction effect, directional long boreholes in roof should be arranged in the fractured zone close to the return airway, and the re-compaction area should be avoided in the horizontal direction. The field application results show that the gas drainage process can be divided into growth stage, stable stage and attenuation stage. In the stable stage, the gas concentration reaches 60% to 70%, the pure gas flow reaches 5 m
3/min to 6 m
3/min, and the gas concentration in the upper corner is maintained at 0.3% to 0.4%, the extraction effect is good; the extraction effect decreases in the growth stage and attenuation stage, which is believed to be caused by the failure of the fractured zone to develop to the position of directional long borehole in roof and the destruction of the integrity of the borehole after the borehole height decreases, auxiliary measures can be taken to strengthen extraction in the adjacent coal seam and goaf in these two stages.