短語詞組短語longwall actual mining 走曏長壁廻採longwall advancing mining system 長壁採煤法longwall advancing mining stope 長壁式廻採工作麪longwall advancing mining workings 長壁開採法longwall shrinkage mining method 畱鑛全麪法longwall advancing mining stoping 長壁採鑛法longwall advancing mining slicing 長壁分層採鑛longwall advancing mining retreating 長壁後退式廻採longwall advancing mining mining 長壁式開採 返回 longwall mining