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 concrete structure地下混凝土结构underground pedestrian walkway行人隧道Underground mined - out zone采空区underground gas-storage well储气井underground monitoring station井下监测站underground coal mining method地下采煤方法underground handwritten copies地下手抄本小说underground building functions地下建筑功能underground cavern development地下岩洞发展underground flexible drainpipe埋地柔性排水管

1. Putting wire underground is safe.
   铺地下电缆是安全的。
2. Power is fed into the electricity line through an underground cable.
   电力通过地下电缆传输给这条电线。