Design Optimisation of Deep Pile Foundations Installed by Static Forces

This paper presents preliminary experimental and analytical investigations of the push-in pile concept, which aims at installing piles in the offshore environment without significant underwater noise. The concept replaces a large diameter pile with a cluster of closely spaced smaller piles. The piles are installed progressively by cycles of jacking. During each cycle, a pile is successively pushed downwards or moved upwards while used as a reaction pile. This process was physically modelled in a geotechnical beam centrifuge and a predictive model was developed and calibrated against these tests. A parametric study was then undertaken to optimise the cluster design and reduce the tool weight necessary to achieve a given installation depth or cluster capacity. Smaller pile diameters are more beneficial to reduce the necessary tool weight during the cluster installation, but require considerably longer piles to achieve the target capacity. The full optimisation of a cost-effective pile cluster will require additional constraints, such as the lateral capacity (not investigated here) and expected installation time.