manhole collar

例句：

1. 1. The manholecollar was a crucial part of the construction.
   人孔盖是施工中至关重要的部分。
2. 2.The engineer had to replace the old manhole collar with a new one.
   工程师不得不用新的人来更换旧的人孔盖。
3. 3.The manhole collar is designed to protectthe workers from falling debris.
   人孔盖的设计是为了保护工人免受坠落物的伤害。