关键词: 关键词：大孔径, 一次成孔, 施工工艺

Abstract: Abstract: the gas concentration drainage borehole drilling project is more common in recent years, the main characteristics of borehole diameter is large (generally aperture between 600 mm - 1000 mm), high hole inclination (usually less than 5 ‰), within the next 500 mm - 800 mm Ф Ф casing. The general construction technology is now in slim hole construction (215 mm) diameter is commonly Ф then gradually expanding (typically four), and the construction technology is relatively complex, drilling risk, construction period is longer, drilling cost is high, the drilling hole inclination cannot assure, casing is more difficult. Tuen mine gas drainage borehole construction, we adopt a pore forming construction craft, to overcome the above construction difficulties.