Why Geotech is key to having the best foundations designs on the market

And why it’s the foundation to Wood Thilsted’s design process

Nov 26, 2021 | 5 min read

We caught up with Paul Gibbs, Wood Thilsted’s Associate Director and Head of Geotechnical Engineering and Design, to understand more about Geotech and how it feeds into Wood Thilsted’s approach to cutting edge monopile design.

Why is Geotech so important?

I might be biased but…I think it’s very important, it’s the start of the process but can have a huge impact on the finished product. Our process starts with a desk study to find out about the ground and site conditions - are there any geohazards which would cause challenges? Underneath the seabed you can have variation in soil type, it might be too hard or too soft or a variety of both! This will bring challenges. Other issues we’ll be looking for are the behavior of the shallow soils, boulders and obstructions on the sea floor – anything that might cause problems with putting in foundations or cable design and installation. Then we’ll analyze all this against ground modelling data and where we’ve gone in to get soil samples to see if they tell the same story. At Wood Thilsted we manage all the early site investigations in house, we’ll send the samples to the lab for analysis and manage the surveys from a technical point of view. What this does is two-fold – it allows us to have access to all elements of the site investigations process, we can question data and have full access to the whole picture from the start and resolve issues early. It also allows us to influence the project development from the beginning – making sure that the final foundation choice is best suited to the site, which can result in huge cost savings later down the line - as well as a much more efficient and effective foundation design. So, it’s no underestimation to say that Geotech is key to having the best foundations designs on the market, and that Wood Thilsted can manage it all under one roof.

What affect does Geotechnical Design have?

I think the fundamental point is early Geotech input, obviously if you are putting anything into the ground you are going to consider Geotech, but at Wood Thilsted we are there at the outset. The more targeted you can be the more value you are going to bring, so you know where to put the effort in. Having detailed knowledge of a site and ground, what the soil is like, what the different layers are like and how they interact is crucial. There may a scenario whereby you have some gaps in your data despite even the most rigorous site investigations. For example, you may not know what soil conditions are like in the last 5 meters of where your monopile is going to go because there are limits to the soil investigation methods. Often when this is the case you have to err on the side of caution and assume the worst-case scenario (for example that it’s clay soil rather than sand), which usually means deeper monopiles, more steel, larger infrastructure to produce the monopiles and larger vessels required to transport and install them. Over a large area this produces significantly more cost, not to mention carbon emissions. However, if you have access to all of the data, and we as the Geotech team have done our job properly, we can challenge any data gaps. We can be confident of how the soil layers will work which means we can influence the design of the piles. Really good Geotech work gives you the confidence to be accurate with your monopile design development which transmits later down the line influencing the final design of the piles and ultimately to huge savings on the steel.

What’s different about Geotech at Wood Thilsted?

Well, I think there’s several things really, firstly as a geo leadership group many of us have previously worked for a client, so we know what is needed for project development, how to best manage risks and budgets and interfaces to other packages etc. Combine that with our bespoke in-house software and our ethos for constant interaction and collaborative working with the other disciplines within the company then we believe we deliver a really integrated approach. Even within Geotech, there are two different disciplines, that of the site investigations and then the actual Geotech interpretation and design which results from the site investigations, and both of those work together seamlessly at Wood Thilsted. Having the entire foundation design process from Geotech and Geophys, to Energy and Climate Analytics and Structural Engineering all under one roof means each area is seen as just part of the bigger picture, rather than each area being a separate entity. So, it’s more of a holistic approach which makes the whole process more nimble and agile. We have such great experience within the team, we’ll take data from the Geophys team, we might want to hone-in-on a particular area, for example you might find a channel in the seabed which can be problematical, so we’ll go back and look in more detail. It’s a constantly evolving picture and we are always working between the different disciplines. Eventually there will be some foundation concept designs, a characterization of the site with some soil profiles, which we’ll give to the Structural Engineers. As we learn more, we’ll refine everything, we’re always moving towards a final ground model and foundation. This is fairly unique to Wood Thilsted because you have all the information, you don’t have to take things at face value. We know the history of the data, how it was collected and why, which gives us the confidence to challenge ideas and ultimately influence the very best foundation design for each particular site. There is no silo working where you receive the data and detail of a site in isolation. The whole process just means frictionless borders between all the different expertise.

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