CACTUS

Climate Adaptation Control Technologies for Urban Spaces (CACTUS)

Academic Team: Dr Katerina Tsiampousi, Prof. Dave Potts, Prof. Lidija Zdravkovic (Imperial College London)
Prof. D. Toll (PI), Dr K. Jonson, Dr P. Hughes, Dr A. Osman (Durham University)
Prof. S. Glendinning, Dr C. Davie, Dr R. Stirling (Newcastle University)
Dr Anthony Leung, Dr A. Bengough, Dr J. Knappett, (University of Dundee)
Prof. S. Tripathy, Dr S. Rees (Cardiff University)
Dr V Sivakumar, Dr S Donohue (Queen’s University of Belfast)

Imperial Post-Doctoral Research Associate: Dr Alexandros Petalas (Imperial College London)

Funding: EPSRC and industrial sponsors
Duration: January 2018 – December 2023

Overview
CACTUS started in January 2018 with funding from EPSRC (£2.2M FEC) and Industry (£135k; contributions from AECOM Ltd UK, Arup, Geosynthetics Ltd, Royal Haskoning, Northumbrian Water Ltd, Skanska Technology Ltd, Transport NI, NHBC National House-Building Council, Welsh Local Government Association, Welsh Government).
It is a collaborative research project between Imperial College, Durham University, University of Newcastle Upon Tyne, University of Dundee, Queen’s University Belfast and Cardiff University, aiming to develop climate adaptation control technologies for urban spaces (towns and cities). Novel composite barrier systems are being developed which will limit the impact of extreme rainfall events and long-term climate change on urban geo-infrastructure.

Background
As precipitation events become more intense, and warm and cold temperatures acquire greater amplitude because of climate change, severe flooding, extreme drying and freezing and thawing pose an increasingly serious threat to geotechnical infrastructure. Retaining structures, road subbase, shallow foundations, buried utilities are few examples of affected infrastructure. The costs of damage due to shrink/swell movements on clay soils have resulted in economic losses of over £1.6 billion in the UK during drought years.
Developing "climate adaptation composite barrier systems" which can prevent movement of water into the soil below foundation level or into zones of backfill behind retaining walls has the potential to limit the impact of a changing environment on geotechnical infrastructure and increase their engineering sustainability and resilience.

Collaborative Research
The Cardiff, Queen’s Belfast and Durham teams are working in close collaboration to identify through laboratory experiments a range of potential soil types (homogenous and composite) that will meet the desired requirements of climate adaptation engineered barriers (hydraulic conductivity and water holding capacity).
The researchers at Dundee and Durham are exploring suitable vegetation types that can enhance transpiration and provide ecological balance and quantifying carbon capture potential of the barrier systems.
Using physical (1g and centrifuge tests) Queen’s Belfast, Dundee and Durham are developing adaptation measures and are quantifying their effectiveness in mitigating potential issues.
Imperial, Durham and Newcastle are developing with the aid of numerical analysis design protocols which can account for current and future weather patterns in the UK and be applied to the whole-life cycle of the barriers.
A trial implementation is taking place in Newcastle to evaluate the feasibility of employing the new technologies at full scale and to develop construction protocols.

Research at Imperial College
Our research is aimed at developing design protocols for the barrier systems. To this end, we are using the in-house numerical code ICFEP to assess the effectiveness of the proposed adaptation measures for water holding and prevention of water ingress/egress in underlying soils under current and future weather patterns. We are identifying and proposing modifications to the soil properties (permeability, compressibility) of the engineered barrier, and we are exploring the effect of soil-atmosphere interaction. We are modelling the unsaturated soil behaviour of the compacted layer carefully using our advanced constitutive, permeability and soil-water retention curve models. Complex, highly non-linear boundary conditions that we have developed simulate the effects of precipitation and vegetation on the barrier. We are extending the capabilities of ICFEP to model freezing-thawing in addition to drying/wetting cycles.