Research on fine design method of pre-drainage zoning borehole on high gas working face

At present, single borehole spacing is generally used to pre-drainage gas on high gas working face. But in the design of pre-drainage boreholes, influence of geological structure and other factors on the design of pre-drainage area are not considered, and relationship between extraction time and borehole spacing is also not accurately analyzed under condition of drainage standards. As a result, pre-drainage design of mining area on working face has not realized fine design of classification and zoning. For the above problems,taking 3603 working face of Huoerxinhe Coal Mine as research object, a fine design method of pre-drainage zoning borehole on high gas working face was proposed, which changes the extensive design mode of single borehole spacing from final line to open-off cut. Firstly, according to the geological conditions of the working face, the pre-drainage area is divided, and the extraction time of each area is determined by mining plan. Then, the pre-drainage hole spacing of each zoning area is determined according to the numerical relationship between the extraction time and the borehole spacing under different extraction rates, so as to realize the fine design of the pre-drainage area. The field test results show that compared with the original design, extraction time is reduced from 8 months to 6 months, and borehole engineering quantity is reduced from 319 440 m to 154 960 m; during observation period, the volume fraction of gas concentration on the whole working face does not exceed 0.58%, and there is no over-limit phenomenon.