Abstract: This paper aims at the problems of low drilling hole formation rate of non-directional bedding drilling due to hydraulic fracturing of fractured soft and low-permeability coal seam, hole collapse after drilling, and short effective hole section of non-directional penetrating drilling, Combining the comb directional drilling technology with hydraulic jet punching technology, a set of large-diameter directional drilling technology is formed which is suitable for hydraulic fracturing in underground coal mine. Field application shows that: this technique not only solves the problem of hole blockage caused by low hole formation rate and hole collapse after hole formation, but also solves the problem of poor gas extraction effect caused by short effective distance of drilling and small influence range after fracturing, which has a strong guiding significance for gas extraction under the condition of broken soft coal seam in this mine.

Key words: Underground coal mine, Large diameter, directional drilling, Hydraulic fracturing, Hydraulic jet