Binks Institute for Sustainability: Protection of critical infrastructure in developing countries through bioengineering and intermediate technology

Earthquakes create a range of hazards for engineers, key amongst which is the need to keep critical infrastructure such as bridges open in the crucial few hours after the event. A major obstacle to this is soil liquefaction, whereby the earthquake shaking can temporarily cause the soil to lose shear strength and undergo large displacements. This can lead to the sloping ground in the vicinity of bridge approaches flowing downhill and damaging or destroying the bridge, hampering rescue efforts and placing a strain on rebuild resources. Hard engineering solutions exist but are expensive and require specialist contractors, so are rarely employed in the developing world.

A previous Dundee PhD student of Dr Brennan, Ke Wang (“Effectiveness of synthetic fibres as liquefaction remediation”), established that fibrous inclusions in the ground have the potential to reduce displacements in liquefying soil. A follow-up project, funded by the Leverhulme Trust “Influence of plant roots on soil resistance to earthquake-induced liquefaction” (with Prof Bengough of James Hutton Institute) used scale model 3D printed root systems (pioneered at Dundee by Prof Knappett), together with fibres, in a series of physical model tests, demonstrating that even if these treatments were near-surface then they retained potential to limit displacements. Plant roots therefore seem a promising intermediate technology solution for stabilising sloping ground and riverbanks in developing countries – they can be applied without specialist skill, they are cheap, they are sustainable and if selected carefully they could positively impact on the existing ecosystem. However, further work is required, particularly in appropriate species selection, and in verifying treatment efficacy.

At the University of Dundee, we have access to a geotechnical centrifuge and earthquake simulator, which enables small scale models of the ground to be tested at full scale stress levels. This technique has previously been applied to a number of liquefaction-related problems and is a powerful tool for measuring ground response to earthquakes and proving the effectiveness of solutions. This will be the principal method of investigation used. Both named supervisors have extensive experience in earthquake centrifuge modelling, specified and commissioned the UoD facility and have strong international peer esteem in this area. 

The proposed project aims to continue the work carried out in the above projects by bringing bioengineered solutions closer to implementation. Objectives would be (i) identifying the barriers to implementation, (ii) identifying two or three case study sites in different countries where treatment design can be considered (iii) identify target species suitable for engineering each site (iv) create physical models of each species and each site, and carry out a programme of centrifuge testing to measure the response of each during earthquakes and demonstrate how effective each scheme can be (v) based on this experience, create some design rules that can be followed to establish best practice for the method.

This joint engineering-plant science approach will require input from plant scientists, so (as with the Leverhulme project) Ken Loades and David Boldrin at JHI have agreed to be partners and provide valuable multi-disciplinary input.

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