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tap hole , exhaust opening
When advancing and uncovering coal in roadway, better construction method is vibration shot, metal framework, borehole bleed-off and hydraulic hole, of which vibration shot is principal.
井巷掘进揭煤时，较好的施工方法是震动放炮，金属骨架，钻孔排放和水力冲孔，尤以震动放炮为主。
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