A numerical study on the group effect for offshore piles in clay under lateral loading

Abstract

Pile group foundations are widely used in the offshore industry to support large jacket structures, such as oil platforms and substations for offshore wind farms. The pile group foundations are commonly designed using methods developed for single piles but modified to account for the group interaction effect. The modification for pile group effect has been conventionally based on elasticity solutions or empirical observations from field/model pile load tests. In the past decade, considerable progress has been made with respect to modelling single pile response under lateral loading in clay. However, there appears to be limited progress for modelling pile groups in the offshore industry. The design practice has stayed unchanged for several decades. This paper presents a numerical study in an attempt to come up with design recommendations for typical pile group configurations used in the offshore industry. A comprehensive numerical investigation of the group effect for several typical pile group configurations are performed, examining the effect of pile spacing and the loading direction. From the parametric analyses, the so-called p and y modifiers which are to be applied to correct the single pile p-y curves for consideration of the group effect are proposed. An example is presented to demonstrate the application of the modifiers.