短語詞組短語underground col mining 地下采煤underground coal mining 地下采煤underground E mining 地下開采Underground melting mining 地下熱熔開采underground d mining 地下采礦underground coal mining method 地下采煤方法underground bench mining 井下梯段采礦法underground trackless mining vehicle 地下無軌采礦車輛 返回 underground mining