Floating Wind and Ground Risk - New Thinking Required? - Part 1/3
A personal view from Mark Finch, Managing Director
I spent 4 years at Manchester University in the late 80’s studying civil engineering. In amongst the Haçienda, The International and Red Wedge – engineering, mathematics, fringe politics and music were my passions.
A lot has happened in the last 30 plus years but my fascination with complex engineering problems has stayed with me.
Since graduating, I've worked in offshore geotechnical engineering all around the world. I've been lucky enough to travel to many amazing places (from Russia to Alaska via Australia and South Africa) and spend much longer periods in London, Congo, Newfoundland and Paris (but mainly Scotland).
I've had the good fortune to work with some brilliant engineers and had mentors, teachers, colleagues, and friends who continue to be unbelievably generous with their time, energy and support. As Freddy Mercury said "I thank you all…"
I've been 'the soils guy' for offshore wind developers, oil & gas operators, consultants and contractors for many years now. One of the most common things I get asked is some variation of "Why should we spend all this money on a survey?" or "Do we really need a survey?" "We've done this loads of times before without any problems."
There is an often-quoted adage in geotechnical engineering that, 'you will pay for a survey whether you do one or not.' I disagree. You might pay for a survey many times over if you don't do one. You might also get away with not doing a survey and not have to pay at all – but remember, you are getting away with it. Every time you don’t do the right thing, you're taking a significant technical risk (however considered) and, in my experience, not doing the right thing will catch up with you in the end. Prof. Littlejohn is frequently quoted from his 1994 ICE publication 'Without Site Investigation Ground is a Hazard' and if you haven't seen the leaning tower of Pisa cartoon to reinforce the point, where have you been for the last three decades? But there is little definitive information to link poor ground risk management to project cost and schedule overruns.
Most engineers take the link to be self-evident – myself among them – but hard facts and causality are elusive. I understand there will be a paper on this very issue at the SUT OSIG conference this autumn. This is very welcome and long overdue.
But why does all this matter?
The ultimate result of inadequate survey and/or poor interpretation of the results is design conservatism. The result of design conservatism is, ultimately, cost – often lots of it. 'An engineer can do for a dollar what any fool can do for two.' Wise words from Arthur Wellington in the late 19th century. Any foundation can be made to work just about anywhere – if you're prepared to pay for it. This, in my experience, is the reason why site survey is often not taken that seriously. Conservative foundation design can hide a multitude of sins. Most of the time.
There is a reason why most offshore structures are piled with traditional tubular piles. To many – and particularly those who have been lucky enough not to know the pain of ground related issues – the seabed can be an irritation. But, as we move into XL and XXL monopile design and, floating wind anchor design, conservative design because of poor data or interpretation can have a disproportionate impact on your project (potentially far more than for piled jackets). It's (past) time to take notice.