Study on gas drainage technology of large diameter horizontal borehole bridging goaf

In view of the problem of gas control in the return air corner of "three-in-two-return" ventilation system under the condition of high-intensity mining in thick coal seam with high gas content, by optimizing the ventilation mode of mining face, a partial "Y" type ventilation mode was formed in the working face.Combining with the construction technology of large diameter horizontal drilling, a gas extraction technology of large diameter horizontal drilling bridging goaf was proposed, which was applied to gas extraction in goaf of fully mechanized top coal caving face in Baode Coal Mine.The results show that: the partial "Y" type ventilation mode can reduce the roadway tunneling in the working face, shorten the preparation period, and create good space-time conditions for gas extraction; the application effect of large diameter horizontal borehole bridging the goaf gas extraction technology is obvious, which can continuously and efficiently implement the closed extraction of goaf, effectively control the gas emission intensity of goaf; large diameter horizontal borehole bridging the goaf gas extraction technology can achieve negative pressure control, which is conducive to further improve the effect of goaf gas extraction, and its extraction branch pipe can be recovered, reducing the cost of mine gas control.