短語詞組短語underground col mining 地下採煤underground coal mining 地下採煤underground E mining 地下開採Underground melting mining 地下熱熔開採underground d mining 地下採鑛underground coal mining method 地下採煤方法underground bench mining 井下梯段採鑛法underground trackless mining vehicle 地下無軌採鑛車輛 返回 underground mining