back-filling in layers

例句：

1. 1. The construction crew was instructed to backfill the hole immediately after excavation.
   施工队被指示在挖掘后立即回填这个洞。
2. 2.The company decided to backfill the damaged area with new soil.
   公司决定用新土回填受损区域。
3. 3. The engineers were required to backfill the gap between the two buildings with concrete.
   工程师们被要求用混凝土回填两座建筑之间的空隙。