By expanding the diameter of bore,enlarge the exposure area of coal bed and discharged pressure range and increase the discharge of gas.As a result,improve the draw and discharge effect of bore.

• 通过扩大钻孔直径,达到增加钻孔的煤层暴露面积和卸压范围,增加钻孔的抽排瓦斯量,提高钻孔的抽排效果。