A.15-30m B.30-45m C.45-60m D.60-75m
A.40mB.50mC.60mD.80m
A.明洞開(kāi)挖前,洞頂及四周應(yīng)設(shè)防水、排水設(shè)施 B.明洞應(yīng)自下而上開(kāi)挖 C.開(kāi)挖松軟地層邊、仰坡應(yīng)隨挖隨支護(hù) D.明洞槽不宜在雨天開(kāi)挖