Lid construction

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The top-cover construction method is a construction method for creating tunnels and excavations .

For this purpose, a diaphragm wall or a bored pile wall is first created from the top of the terrain . With the help of bored piles , intermediate supports can also be created. A cover is then poured onto the walls and supports. This cover is mostly made directly on the ground or on a bed of sand, without any lower formwork. The evenness of the cover is ensured , for example, by creating a blinding layer from lean concrete and a PE film . Then the floor under the lid can be dug out.

The advantage of the top-down construction is, among other things, that the terrain surface is available again relatively quickly for traffic and other uses, since the excavation takes place under the top.

Further advantages are:

  • The cover serves as a head stiffener, i.e. horizontal earth loads that act on the diaphragm / bored pile wall do not have to be absorbed by temporary anchoring or clamping in the ground and can be transferred directly to the cover.
  • With a rigid connection of the cover to the slotted / bored pile wall, the thickness or the bond length of the slotted / bored pile wall can be reduced.
  • Scaffolding for the cover plate is not required.

The Düsseldorf lid is a special type of lid .