Pile Caps and Ground Beams.

Many piled foundations consist of a number of relatively small-diameter piles and they require a practical driving tolerance. Pile caps or capping beams are required to accommodate this tolerance and to pick up varying widths of super-structure elements. In some situations, where large-diameter piles are used, pile caps or beams are unnecessary.

However, this is the minority case. The caps consist of  concrete pads or beams constructed at the head of the piles to provide the connection between the pile and super-structure (see Fig. 9.44).

In addition to transferring the vertical load from the super-structure to the foundation, there is often a need to provide lateral restraint to the tops of the piles, particularly where less than three piles are provided. For small low-rise developments (single- or two-storey construction) the amount  of restraint required to the tops of the piles can be provided by the use of the ground floor slab or a lightweight raft foundation (see Fig. 9.45).

Fig. 9.44 Pile caps.

Fig. 9.45 Pile cap/beam restraint.