High Flow Gas Drainage Technology of Goaf Under U-type Ventilation System for Large Mining Height Stope

In order to solve the safety hidden danger of ventilation in goaf of multi-lane ventilation system and the problem of gas over-limit of “U” ventilation system in large mining height stope, we proprosed the large flow pumping technology in goaf by using large flow through beds holes in “U” ventilation system combining with directional drilling in medium-high fracture zone, and optimized the directional drilling and the distribution parameters of through beds hole. Field application of large mining height shows: the extraction flow of large diameter borehole of φ153 mm is 2 to 3 times that of φ96 mm, the gas extraction concentration of the drilling in the middle and high fractured zone is about 2.4 times that of the middle and low drilling; gas extraction effect is best when the spacing of large flow through beds hole with the diameter of 250 mm is 5 m. The concentration of gas in the upper corner remained at 0.55% to 0.6% after the adoption of large flow drainage technology, avoiding the gas over-limit.