Serviceability Limit State Design: Base Response of Screw Injection Piles

Screw injection piles are a type of screw displacement pile that, much like grout anchors, use grout injection to reduce the installation resistance and to displace soil around the enlarged pile tip. In doing so, noise and vibrations are greatly reduced and the displacement mechanisms associated with installation are considered to beneficial to the overall pile capacity. While these benefits have increased the uptake of screw displacement piles in the industry, divergences in design standards means there is no consensus on the axial response of these piles, particularly with regards with their full load-displacement response. This paper gives a short overview of current serviceability limit state design and compares base resistance measurements from two different pile test sites to evaluate the predictive two settlement prediction methods. A stiffness-based formulation gave good estimations of pile displacement when compared to the load test measurements and is able to generalise well across both test sites. With effective ways of predicting pile displacement, more benefit can be gained out of load tests to low displacements, providing an effective means of checking the in-situ capacity of a pile after installation or in the context of foundation reuse.