Exploring the lateral capacity of squat piles in soft clay through geotechnical centrifuge modelling

Abstract

Many offshore structures currently in use are supported by piles with large length-to-diameter aspect ratios, because it is well known that such foundations can hold large forces and moments. In environments where long piles are not suitable, structures will use foundations with very low aspect ratios such as skirts and mats. Capacity of long piles has been studied for decades and is well documented, whilst more recent tests have also addressed the behaviour of skirts, mats, and other low-aspect ratio foundations. The vertical and lateral capacity of mid-size foundations, with aspect ratios between one and five, has generally been thought too low for the requirements of most offshore structures. However, in recent years, structures of increasingly different shapes and sizes have been used in offshore environments, such as water-based renewable energy sources or marginal oil and gas platforms. In many of these cases, the usage of a low aspect ratio foundation could significantly reduce installation and transportation costs. Limited studies have been performed on such foundations, and most of the existing work uses only analytical and numerical solutions. Geotechnical centrifuge tests and corresponding numerical analyses were started at Texas A&M University and were continued at the University of Cambridge on the lateral capacity of piles with an aspect ratio of two in normally consolidated clay. Piles were loaded under both pure rotation and a mix of rotation and translation. This work is relevant to offshore structures requiring foundations that are strong but easily installed and cost-efficient, specifically structures secured with piles that experience point loads either through or above the water. It is also of interest for structures in difficult environments, such as areas too shallow or sedimentary for long piles or too fragile for skirts and mats.