Kvaerner Cementation Foundations has developed a range of specially adapted enlarged head formers for driven cast insitu piles or bored cast insitu piles installed using rotary auger or CFA equipment.
The company says the requirement for integral enlarged pile heads has increased as engineers and contractors look for the most efficient and economical foundation solutions for their clients.
Typically, the technique is used where piles are installed in a square or triangular grid pattern to support (with or without load transfer platforms) floor slabs, raft foundations, hardstanding areas, and even road embankment supports.
Head formers can be driven or drilled into the ground as piling starts or at the end of concreting, depending on the piling method and ground conditions. They are generally cone shaped and up to 900mm diameter, although square heads can be used.
Enlarged pile heads reduce the effects of punching shear, which results in more economical slab construction and, as the head is an integral part of the pile structure, removes the need for pile trimming. Under-slab gas barriers and waterproofing membranes can be laid directly over pile heads, which also eliminates expensive trimming and sealing around pile shafts.
A particular construction difficulty of enlarged head piles is ensuring the integrity of concrete in the head as the former is withdrawn. Addressing this, Kvaerner has recently developed a specially built reinforcing cage which can be inserted in the enlarged integral head to give it structural capacity. Reinforcement can project through the enlarged pile head or stop below finished head level, depending on design requirements.