After the operations of excavation, and if needed, sheet piling and … to make sure of the status of the flooring of the manhole, concrete slab should be used, in which case pre-made slab could be used to speed up the operation.
The thickness of this slab is about 15 centimeters and C16 concrete is at least used. After we proceed to install the manhole and implement the connections to the pipes.
After finishing the implementation of connections, in order to prevent the manhole from floating, we should proceed to implement the anchor key according to the standard.
For this purpose, we use C20 concrete from the base part of the manhole to the height of about 1 meter. So that the concrete is at least 20 centimeters higher than the top of the polyethylene manhole’s sole part’s ring.
After setting, this concrete will anchor in the manhole ring from one side and in the trench wall from the other and in such way, regarding its own weight, the concrete prevents the manhole from floating.