Asset deterioration and degradation modelling of earthworks

Reflecting on recent discussions within the Geotechnical Asset Owners Forum (GAOF) Iain McKenzie, Principal Geotechnical Engineer, Welsh Government, provides his own perspective on the challenges, needs and opportunities associated with asset degradation modelling of earthworks.

Everything tends towards chaos. What’s true in thermodynamics turns out to be true for the earthworks supporting our transport networks. Perhaps chaos is too strong a word; maybe “managed decline” would be a better way of putting it. Everything tends towards a managed decline. Not quite as snappy perhaps but I guess for those of us managing geotechnical assets, the question should be – is this actually a universal law or is there something we can do about it?

The topic of “Asset Degradation” was the theme of September’s meeting of the Geotechnical Asset Owners Forum, focusing on the various challenges, needs and opportunities we face and, from my perspective (speaking from the Transportation Department of the Welsh Government looking after the trunk road and motorway network) it was heartening to hear our problems are not unique.

Wales has roughly 3,500km of earthworks along its strategic highway network. Cuttings, embankments, rock slopes. Many of them old and much of it built on sidelong ground following ancient routes though the hills. Gravity, time and the elements all take their toll.  But what are the biggest geotechnical challenges facing asset managers at the moment? In my opinion, amongst the many issues, some stand out.

Firstly, there’s environmental change, and specifically, the increasing number of high-intensity storms experienced each year. Wales feels very susceptible to these events; storm force winds and torrential rainfalls stress the network and while (bar the odd small retaining wall failure, the network seems to have got away with it relatively unscathed), we’ve definitely been repeatedly testing the same areas again and again for the last few years. 

Then there’s increasing demand and this come in two distinct forms; increased traffic numbers and the increasing length of the asset we maintain. New roads and assets continue to be built and sometimes the old assets need to be adopted as well – the net result is the pressure on budgets goes up.

Finally, amongst the challenges, there’s complacency; outside engineering circles, there seems to be a widely-held perception that as long as nothing’s collapsed, then everything’s fine.

So, is there anything we can do? How can we stop it raining in Wales? Could we make the country a bit flatter in the middle, get rid of some of those pesky mountains maybe? Well, there are probably some things we need to start doing better (and, I hasten to say, this is my personal opinion).

We really need to upgrade our drainage assets. It’s almost always water that’s the cause of any problems. This is not however going to be a quick fix and it’s not always easy to resolve; we recently did some (fairly non scientific) investing into our flooding hotspots and, in South Wales at least, concluded that at roughly a third of the sites, the highway drainage worked perfectly well provided enhanced maintenance is carried out, i.e. extra trips out to clear trash screens and clear debris from catch pits.

Another third of the sites we’re probably never going to be able to resolve without major re-engineering works. But that left roughly a third that could be significantly improved by relatively simple capital upgrade schemes and it’s these we need to target first. In conjunction with this, when building from new, we need to construct more resilient and easily maintainable geotechnical assets.

We already have systems in place to try and control this process but at the moment we’re still generating avoidable problems such as ground anchors built behind walls we struggle to test and reinforced soil slopes covered in flammable gorse bushes. As an overseeing organisation we need to influence these designs at an earlier stage. These things are getting better, I think, but there’s still work to do.

And for the optimists amongst us, there are opportunities too, regardless of the economic climate. First amongst these, the great hope, technology; satellite technology, remote monitoring via drones, laser scanning, lidar, fibre optic acoustic sensing, shape accel arrays, elctrokinetic geosynthetics. There’s a lot of new work happening in numerous fields. Time will tell what emerges as the most useful. 

Secondly, there’s the power to influence things for the better; in Wales at least, there is a pretty small pool of senior managers, civil servants and politicians to convince that action needs to happen. It’s actually a remarkably short chain from the highways inspectors tramping the network to the Cabinet Secretary with Ministerial responsibility for the Economy and Infrastructure. Small is beautiful, sometimes.

And finally there’s knowledge sharing; in this day and age, this is undoubtedly  faster and easier than ever before, and the long term asset management of geotechnical assets is now a well established area of work and learning from others and their experiences is invaluable. This is of course, very much the reason the Geotechnical Asset Owners Forum exists.

So perhaps not everything necessarily heads to a managed decline? Maybe it should be “everything tends to a managed state with intelligent mitigation measures and planned series of appropriately timed strategic interventions”? That’s really not very snappy, I think I might need to work on this more…

Iain McKenzie, Principal Geotechnical Engineer, Transportation Department of the Welsh Government
November 2016

To find out more and engage with the Geotechnical Asset Owners Forum (GAOF), visit www.gaof.org

CIRIA have a part-funded proposal P2730 Deterioration and degradation modelling of infrastructure assets (P2730) to take forward a programme of work that will enable organisations involved in asset management to share, compare and contrast their approaches to predictive modelling and utilisation of associated decision-support tools. Acknowledging what others are doing across different sectors and learning from their respective developments should be an empowering exercise for all involved.

Click here to find out more about P2730