underground air矿内空气undergroundadj.地下的；秘密的adv.在地下；秘密地n.地下；地铁；地道；秘密活动underground pipeline detection地下管线探测underground teaching evaluation本科教学评估underground gasification mining地下气化开采underground roadway engineering地下巷道工程underground silo-enclosed bin地下圆筒围仓underground commercial resource地下商业街Underground metal water conduit埋地金属水管道underground pipeline protection地下管线保护underground pipe heat exchanger地下埋管换热器underground objects orientation地下目标定位