laying of pipes

例句：

1. 1. Theengineer laid down the first layer of concretefor the new road.
   工程师为新路铺设了第一层混凝土。
2. 2. The plumberhad to lay down anew pipe in the basement.
   水管工不得不在地下室铺设一条新管道。
3. 3.The construction crew was laying down the foundations for the new building.
   建筑工人正在为新大楼铺设地基。