A.φ48㎜×3.5㎜ B.φ50㎜×3.5㎜ C.φ55㎜×4.5㎜ D.φ48㎜×2.2㎜
A.沉管成孔 B.泥漿護壁鉆孔 C.人工挖孔 D.振動沉管成孔
A.50% B.100% C.75% D.25%