Pile supported slabs are considered as “deep foundations” and are introduced after geotechnical investigations have determined that the ground is inadequate for a ground supported slab.
Where pile-supported slabs are used, the sub-base is assumed to recede in the long-term, leaving the slab supported solely by the piles. However, the sub-base provides temporary support for the slab during construction until it has set enough to support itself.
In the UK, all piles are designed in accordance with Eurocode 7.
It is most common to reinforce pile supported slabs with fibre rather than fabric. This is because the piles induce a hogging bending moment and it would be either very complicated or very expensive to arrange fabric reinforcement so that it will resist the both the hogging and sagging moments in the slab.
Because of this, sawn joints are not used in pile supported slabs. Pile heads are normally installed at the top of the pile in order to decrease the slab’s effective span and to reduce the stresses on the slab. The pile head must be constructed with a fairly tight tolerance, flush with the sub-base during construction to minimise restraint to the slab during its early shrinkage.