Automatic drainage technology of downward drilling holes in parallel in water-bearing coal and rock seam

A large amount of water generally accumulates in the downward gas drainage boreholes of the water-bearing coal and rock formations, which will cause the borehole blockage and reduce the effective airflow crosssection, and affect the coal seam gas migration and production and the stability of the borehole wall, and seriously restrict the gas drainage effect. In order to solve the problem of water accumulation in the downward gas drainage boreholes in the water-bearing coal and rock formations, this paper adopts the technology of multi-hole parallel automatic drainage, develops the downward drainage drilling automatic drainage system, and designs the multi-hole parallel drainage pipeline arrangement. By lowering the drainage pipeline into the borehole, and using the collection and drainage pipeline to realize the parallel connection of multiple downward drainage borehole drainage pipelines, the mine explosion-proof and intrinsically safe programmable control box controls the mine electric valve and under the coordinated work of mine drainage pumps, multiple downward drainage drilling holes are automatically circulated and drained. This technology overcomes the disadvantages of compressed air drainage on the stability of boreholes and cinder blockage of the drainage pipeline, and does not affect the normal gas drainage of the drainage boreholes, achieves the purpose of intensive and efficient drainage, and improves the degree of automation of underground borehole drainage. The results show that through the application of multi-hole parallel automatic drainage technology in the,3307 working face of a coal mine, there are a total of 5 holes drilled in the downward direction, with a drilling inclination angle of 3°～15° and a drilling depth of 75～100 m. The drainage pipeline and the collection drainage pipeline adopt 25 mm and 50 mm mine PVC pipes, and the system sets a single-hole automatic drainage time of 2 min. The concentration of single hole gas drainage in the investigation test borehole increased from 5%～13.8% to 23.3%～53.6%, an increase of 2.19～3.87 times; the scalar volume of single hole gas drainage increased to 0.028 9～0.052 4 m3 / min, an increase of 1.68～2.94 times, which significantly improved the effect of gas drainage, effectively solved the problem of water accumulation in gas drainage borehole under water bearing coal seam, and ensured the smooth flow of gas drainage channel of the borehole.