Researchment and Application of Comb Type Directional Borehole Drilling Technology in Underground Mine

According to the present poor borehole complement of the gas drainage borehole in the soft seam, short gas drainage distance, small drainage area and other difficulties, the comb type directional borehole method was applied to the comb type borehole drilling with a long distance in the roof and floor strata of the soft se am and thus a longdistance and regional gas drainage in the soft seam could be conducted.According to the construction features of the comb type borehole drilling in t he soft seam and to the rational selection of the comb type borehole pattern, the emergent branching operation of the comb type directional drilling in the roof and floor strata of the soft seam, the reduction of the drilling tools friction resistance and other technical difficulty were analyzed.The site trial showed that the time control contin ued sliding drilling was applied to make the branching of the comb type drilling in the rock strata.With the optimized design of the borehole and the high accuracy contro lled borehole tracing, the friction resistance of the drilling tools could be effectively reduced, the safety of the comb type drilling operation could be improved and the re quirements of the max borehole depth over 500 m and the branching operation in the rock strata could be met.