摘要
在无解放层可采的突出煤层，最普遍采用的是打钻防突措施，增大钻孔直径使抽排瓦斯防突效果更为显著，ＢＺ１５０－Ⅱ型自动变径扩孔钻具以小孔径钻进、退钻扩孔、孔内可自动收缩，从而达到事半功倍的防突目的。
Abstract The most popular method to prevent outburst for outburst prone seam without protective seam on go drill boreholes to drain methane.The effect will by more sygnificant with holes'diameter emlarged.BZ150 11 drilling tool with auto varying diameter,reaming can drill holes wigy small diameter,ream while withdrawing and automatically contract in holes so as to attain the goal of outburst pervention.
