The main objectives of the project are as follows:
- To develop screw pile geometries for offshore use as foundations (e.g. within jacket structures or monopods) and infuture floating systems (e.g. as anchors) that are optimised for installation
efficiency and performance under in-service loads.
- To improve prediction of installation torque requirements for new and future screw pile geometries in a variety of soil types.
- To prove the performance of new and future screw pile geometries subject to representative offshore loading for current water depths and wind turbines, and future aspirations.
- To understand efficient deployment and performance of multiple screw piles acting in a group or as part of a structure with multiple individual foundations.
- To synthesize objectives (1) - (4) to develop design and decision making tools (e.g. single or multiple screw pile deployment, pile sizing, installation requirements and prediction of
in-service performance) for offshore wind and the wider offshore renewables industry.
- Disseminate the outputs and findings to the industrial and research communities.
The laboratory-based physical modelling and advanced soil characterisation will create an important case study data set of significant value to the wider geotechnical research community. It
will be useful as a basis for future studies of screw pile
behaviour and for validation of future numerical and analytical techniques with reliable soil input parameters. The
development of new centrifuge installation modelling techniques will be of interest to the physical modelling community attempting to replicate appropriate installation techniques. The results
of the case studies (model and field test) will be
made available to the academic research community through journal publications and conference presentations. Once
these dissemination routes have been achieved the data set will be archived and made freely available
here in spreadsheet form.
The numerical modelling developed in this project will be adaptable to many other problems in computational geotechnics
that involve soil-structure interaction, with major geometrical and soil state changes such as simulations of push in or gyropiling
installation and the in-service response of foundations subject to torque, e.g. offshore foundations impacted by offline
loading or trawl net snagging. In terms of legacy beyond this project it will be trivial for alternative material models to be
implemented within the same numerical framework. The code developed in this project will be full documented (using
Doxygen) and made available for free under a GNU Lesser General Public License hosted as a Google project (or similar).
Source code will be hosted in this public repository and suitably licensed in order to allow for an unrestricted
utilization/modification by academia.
More generally the research will be of interest to the following groups:
- Geotechnical engineering researchers working on offshore geotechnics, linked to applications in renewable energy, e.g.offshore wind, marine energy, oil and gas and onshore foundation design and
- Researchers in computational mechanics who will be able to exploit the code produced, add new material models, new physics (e.g. thermal behaviour) and study solvers for these numerical
- Researchers in biological or agricultural sciences that want to understand the processes of plant root development in soil or the boring behaviour or insects in soil and other materials.
- Structural engineers interested in soil-structure interaction, in the modelling of the interaction of wind turbine structuresabove and below water.
Thus the research is relevant to more than one discipline although initially dissemination and impact generation will be
targeted primarily at the engineering disciplines (single). Outside the time frame of this project a wider impact profile will be
achieved through cross disciplinary dissemination.
Beyond academia this research project will lead to economic and environmental impacts:
- This project will accelerate the development of an alternative foundation system for offshore wind which is expected to carry a reduced overall foundation system cost, compared to currently
proposed solutions which in some cases exceed the manufacturing capabilities of the UK. As renewable energy projects require many more individual installations than oil and gas
applications, small efficiencies can result in huge overall project savings and allow sites to be developed that may currently be considered uneconomic. These reductions in the cost of
foundation fabrication and installation will be passed onto the developer, operator and ultimately to the UK consumer via a reduction in the cost per GW of offshore wind energy generated.
This will also therefore assist in improving the public perception of the viability of offshore wind farms.
- The proposed foundation design tools that will be developed will aid Geotechnical engineers to select the most appropriate foundation solution and deployment strategy to suit the water depth
and geotechnical conditions. This will give enhanced confidence in deploying adventurous foundation types in new environments for offshore wind. This will result in a competitive edge for
UK foundation contractors that will allow them to export their expertise internationally.
- Offshore wind farm developers will be able to choose from a greater range of foundation solutions coupled with subsea structure alternatives (monopod or jacket structures) that give the
greatest economic and performance benefits. Installation contractors will be able to plan, design, build and invest in infrastructure that is appropriately scaled to actual
deployment requirements. This reduction in uncertainty will make it easier to attract financial investment in adventurous and novel techniques. In turn this will give UK machine and
equipment developers economic advantage over competing overseas technology.
- The research will contribute to new analysis techniques that will be implementable in commercially available pile design software (e.g. OPile) and as a module within mooring analysis
(e.g.Orcaflex). This will assist with take up of screw piles as a beneficial alternative foundation technology both onshore and offshore. Development of 3D large deformation modelling that
can simulate complex installation processes (such as screwing a pile into soil and determining the effect on the soil state) and which can then be implemented in a standard FE code has a wide
potential for take up in the modelling of other complex geotechnical installation processes and similar processes in other engineering disciplines.
- The proposed technique will be a comparatively 'silent' approach compared to driven piles. The greatly reduced noise and vibration will be less disturbing to marine mammals. It will
therefore also have an associated additional economic benefit in removing the need for expensive noise-mitigation techniques.
- The installation process can be applied in reverse to 'unscrew' the piles from the ground at the end of the project's life.This ability to completely decommission has benefits over classic pile
types that are either left insitu of cut off below the seabed, thus the site can more easily be returned to its original state. The ability to remove the piles would potentially also allow
re-use in future applications.