Application of bedding directional long borehole in thick coal-seam along top excavating face

Due to large thickness of coal seam along top excavating face, normal borehole cannot effectively extract coal gas from roadway floor, which is easy to cause gas exceeding limit on the excavating face and affect efficiency of roadway excavating. Taking main transport roadway of a coal mine in Shanxi Province as an tested roadway，application of bedding directional long borehole in thick coal-seam along top excavating face was researched from three aspects of parameters design of extraction technology, borehole construction and extraction test by analyzing problems existed in gas control on excavating face. The field test results show that after adopting extraction technology of bedding directional long borehole, gas concentration in return air flow and excavating face of the main transport roadway is stable on the whole during roadway excavating. The average gas volume fraction of the return air flow is 0.34% and the one of the excavating face is 0.16%. Gas emission decreases obviously, which shows definite gas control effect. Compared with extraction technology of normal borehole, roadway excavating is accelerated from 150 m per month to 240 m per month, gas volume fraction of the excavating face is decreased from 0.53%-0.79% to 0.25%-0.48%, gas volume fraction of the return air flow is decreased from 0.63%-0.96% to 0.28%-0.69%, and the total time consumption of excavating 400 m roadway is reduced from 175 d to 138 d, which show that excavating efficiency is improved effectively.