A.1mB.2mC.3mD.5m
A.防止箱身扎頭B.減少開(kāi)挖高度C.支護(hù)開(kāi)挖坡D.導(dǎo)向
A.頂程較長(zhǎng)B.箱身孔徑較大C.地質(zhì)條件不好D.基底堅(jiān)硬