The principle of using the anchor cable support to replace unexploited coal pillars,constructing artificial stone walls and wooden sheds in the channel along goaf is introduced.

 
  • 介紹了用錨索支護代替留設煤柱、人工石墻木棚等留巷技術(shù)的原理;
今日熱詞
目錄 附錄 查詞歷史
国内精品美女A∨在线播放xuan