Unsolved
What is the manufacturing material of the manhole cover? Is there indeed a manhole cover designed and put into production using fiber composite materials? Or is it possible for composite materials to replace steel as manhole covers?
The "paper manhole cover" is actually a fiber composite material, which can be used in subway landscape engineering. It is all located in the green belt and can withstand adult trampling. It is preliminarily determined that the cover will only be damaged unless it is crushed by a vehicle.
