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 prospecting survey井下勘探测量underground conservation pool'underground garage ventilation地下车库通风underground hydropower project地下发电工程Underground plastic drain pipe埋地塑料排水管道underground water-proof wall地下防渗墙underground research education研究型本科教学underground powerhouse caverns地下洞室群underground engineering survey地下工程测量underground directional layout地下方向放线