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When the earth really does move

Image of Dr Esther Norton

When the earth turns to liquid things are not looking good. An ARU project is looking at ways to increase communities’ resilience in the face of the devastating phenomenon of soil ‘liquefaction’.

It sounds like a scene from a sci-fi movie: the earth underfoot starts rumbling, vibrating faster and faster until it starts turning to liquid… what do you do? This terrifying prospect is in fact a phenomenon of many earthquakes and can cause huge amounts of damage, as in recent quakes: Emilia-Romagna, Italy in 2012, Christchurch, New Zealand in 2011 and the Great East Japan Earthquake in 2011.

‘Called ‘liquefaction’ it occurs when the ground is subjected to seismic vibrations and behaves like a liquid. For this to happen certain conditions must be met. For example, it only happens in specific soil types (sand), and in soils in a particular compacted state (loose) and most importantly the soil must be fully saturated with water. If all these conditions apply, the vibrations caused by the earthquake transfer pressure to the water, pushing the soil particles apart, and causing the soil to liquefy.

Thankfully East Anglia – indeed the UK in general – is not a part of Europe known for seismic activity. But a team from our Department of Engineering and the Built Environment is, nevertheless, leading a major new earthquake-related research project. The LIQUEFACT project is funded by the EU under its Horizon 2020 Research and Innovation programme, and runs until October 2019. It is looking at how the effects of liquefaction on infrastructure and communities can be mitigated.

Dr Esther Norton, deputy head of department and a geotechnics expert, explains that although not all earthquakes lead to an Earthquake-Induced Liquefaction Disaster (EILD), those that do often cause the worst damage: “Essentially, if you have a building on this type of strata when this happens, it will literally be floating on a liquid, rather than being on solid ground,” she says. Regardless of how well constructed a building might be, it can “just topple over,” she explains. “Since EILD events generally happen near water, you will find that harbour walls fail and bridges collapse as the soil beneath the piers loses all bearing capacity.”

A lot of research into liquefaction has been carried out, after EILDs in Niigata, Japan in the 1960s through to Christchurch, New Zealand in 2011. What has been less examined, though, is the way in which a community can improve its resilience to such an event. This is where the LIQUEFACT project comes in. “It’s to do with ways of preparing communities to be resilient in the face of an EILD,” says Esther. So the project is looking at critical infrastructure “and coming up with ways of assessing vulnerability, mitigating the risks and improving the community’s resilience.”

With Esther’s specific expertise in geotechnics, she will be using lab and field results from the partners across Europe to come up with “indices that we can apply to any scenario: to extrapolate from the specific to the general”.

The plan is that these indices can be used to predict where liquefaction is most likely to happen, which public buildings are most vulnerable, and how to protect these buildings in terms of retrofitting, design procedures and critical use location analysis.

Five key outputs of LIQUEFACT

  • European Liquefaction Hazard GIS Mapping Framework: a way of identifying the areas in Europe where liquefaction is most likely to happen, mapping seismicity, groundwater and geology
  • Simplified Structural Vulnerability Assessment Methodology: a means of evaluating a building’s vulnerability, on a scale of zero to five
  • Liquefaction Mitigation Planning Framework: how to assess a particular building and identify the best ways to mitigate against liquefaction
  • Urban Community Resilience Model Framework: assessing a community’s resilience to liquefaction induced disasters, on both a sociological and structural level
  • Overall Integrated LIQUEFACT Reference Guide (LRG): A software toolbox that will pull all the project’s findings together, including a cost-benefit analysis for critical infrastructure asset managers

Anglia Ruskin as overall manager

The team is working with six other European universities and several companies who are providing equipment and engineering expertise. Anglia Ruskin’s role is to manage the project, “conducting the cost-benefit and asset management analyses, coordinating and aligning all the research carried out by the various partners as well as overseeing the whole project.”

Professor Keith Jones, Head of our Department of Engineering and the Built Environment, is overall project leader. Esther remarks: “He’s a very good manager, great at working with people. We’ve got individuals from many culturally it can be quite tough keeping everybody on script.”

The make-up of their department has also been key, she believes: “We’re a very multi-disciplinary group – we have civil engineers, mechanical engineers, architects, quantity surveyors, building surveyors and construction managers. A broad spectrum of built environment professionals. So we can take very technical information and make it into real management and asset-management tools that can be used by critical infrastructure managers.”

A very strange feeling

Having begun her own research into earthquakes and liquefaction while living in Chile, Esther has herself experienced earthquakes first hand. “It’s a very strange feeling, but you get used to it,” she admits.

But with an apparent increase in earthquake activity over the last 60 years it seems that, unfortunately, the role of projects like LIQUEFACT and experts like Esther are going to be a vital support for affected communities across the world for many years to come.