Developing Pile Rock Interaction for Offshore Structures

Objective

Offshore wind turbines (OWT) are key to addressing climate challenges and reducing carbon emissions. The deployment of offshore windfarm in Europe relies on the safe design of foundations. Foundations comprise ≈30% of the capital cost of an offshore windfarm and optimisation of their design is paramount in today’s economic climate. As offshore wind farms move into more challenging marine environments where bedrock lies close to the surface, foundation design meets new challenges which can limit expansion. To date the majority of research in this regard has focused on soil structure interaction modelling for OWT foundation design. Limited research has been conducted to understand rock-structure interaction and how the effects of natural and installation induced fractures, and gapping influence the lateral behaviour. Following objectives are underlined: 1. Investigate the underlying mechanism controlling the behaviour of pile foundations in jointed and fractured rock masses. 2. Quantify the influence of rock mass strength and stiffness, degree, nature and extent of fracturing, and pile installation method. 3. Develop new design approaches that can capture the salient features, validating the approaches against available field and model-scale experiments where available. The proposal is divided into 4 work packages: WP1 will focus on numerical modelling using 3D finite element analysis (3DFEA) of typical loading pile scenarios to understand the underlying physical mechanisms and how the response varies with rock mass characterisation, profiles and pile geometries. WP2 will involve the development of 1D models calibrated using the 3DFEA for static loads and WP3 for cyclic loads. WP4 will test and validate the developed approaches by comparison with field data curated from the literature. This study aims to reduce the per pile cost by ~10-15% which will allow the development of larger OWTs - a benefit that will trickle down to many coastal nations in the European union.