Rooting for sustainable performance

Lead Research Organisation: University of Dundee
Department Name: Civil Engineering

Abstract

More frequent intense rainfall events, associated with climate change, increase the likelihood of shallow slope failures that lead to costly disruption of road and rail journeys, with risk to life and property. There have been recent slope failures adjacent to transport corridors in the UK, sometimes disrupting important road and rail routes for days. Vegetation has a stabilising effect on slopes: Plant root systems interlock with the soil, increasing its stiffness and strength. Uptake of water by root systems dries the soil profile, again increasing soil stiffness and strength. However, engineers need to be able to predict the combined root reinforcement and soil drying effects on slope stability, so that vegetation management can be used proactively to decrease the probability of slope failure. Vegetation has numerous benefits over conventional hard-engineering solutions, in terms of burying carbon in the soil, enhancing biodiversity, and improving the aesthetic quality of the environment for society.

This project will develop and test a quantitative coupled hydro-mechanical model for the in-service and ultimate-failure performance of slopes planted with vegetation. Rooted-soil represents an innovative sustainable construction material, with distinct mechanical and hydrological properties, that can be used in geotechnical systems. The model will be applicable to both slopes covered with natural vegetation and slopes where vegetation and soil have been chosen and managed according to engineering principles. The validated model will provide a clear framework for assessment and remediation of slopes with potential for reducing economic and carbon costs.

The model will be developed within a multi-scale continuum modelling framework. It will build on knowledge of the elemental components of the system, working from individual soil-root interaction, to continuum soil-root system, and to complete slope, incorporating spatial variability of materials. Modelling will be informed by X-ray CT imaging of the 3-D deformation of rooted soil undergoing shear, using the micro-VIS facility at the University of Southampton, and by field data from slopes containing established vegetation. Predictions of slope performance will be validated against scaled-slopes in the Dundee geotechnical centrifuge under different rainfall regimes. The geotechnical centrifuge enables the testing and monitoring of small-scale slopes containing roots at realistic stresses, which can be manipulated until the slopes ultimately fail.

Template guidelines will be produced for a manual of combinations of plant species, soils and management schemes for optimum performance of designed soil-plant systems suited to emerging climatic conditions. Example data will also be included to allow cost-benefit analyses when designing for slope improvement using vegetation. The potential to translate research findings into related areas will be investigated (e.g. river banks, sand dunes, flood embankments, agricultural and amenity systems). We will engage with an important group of Project Partners, representing key industrial sectors and infrastructure owners, to facilitate the rapid adoption of research findings.

Planned Impact

It is well recognised that vegetation generally improves the stability of soil slopes, but it is difficult currently for engineers to quantify the likely reinforcement. This project will increase substantially our ability to predict the effects of vegetation on the mechanical properties of the root-soil system, in relation both to direct mechanical reinforcement offered by roots, and to associated change in the soil water regime. Vegetation can be financially more cost-effective than hard engineered facings and soil nailing, whilst environmentally enhancing biodiversity, sequestering carbon, and mitigating local flooding risks. Vegetation can be both aesthetically pleasing and important in stabilising soil in agricultural and forestry systems, as sometimes illustrated dramatically when vegetation clearance results in landslides and soil erosion, occasionally resulting in injury and loss of life.

The proposed research therefore has the potential to impact a wide spectrum of the civil engineering, forestry and agricultural industries, and both private and government owners of land and major infrastructure. This includes:
* Engineering consultants and contractors through better guidance on how to incorporate the effects of vegetation into geotechnical calculations and analyses, and advice on long-term management of vegetation to optimise performance.
* Infrastructure and land owners, through better managed and maintained slopes.
* Insurance industry, who assess risk associated with the integrity of engineered or natural slopes.
* The general public, through fewer disruptions to transport and other services, and other positive environmental benefits such as the aesthetic appearance of slopes, biodiversity and carbon fixation.

At the core of this project is a group of stakeholders (EPSRC Project Partners) composed of major UK industries and academics with an interest in the mechanical and hydrological interaction between vegetation and soil. The Partners include infrastructure owners (London Underground, Network Rail, Highways Agency), their engineering service providers (TRL Scotland, Mott MacDonald, CH2MHILL), and research and development organisations (Rail Safety and Standards Board, Forest Research). They will provide a client's and practitioner's view of the benefits of the research, thereby helping to direct its development and dissemination.

All of the Partners have provided Statements of Support that explain how they will contribute to the research, the benefits that it will bring to their organisation, and how they will help to ensure impact. The major inputs into the project by the Partners will be: attendance at and hosting steering meetings and workshops; reviewing detailed research findings; dissemination within partner organisations, including via presentations and meetings; authoring of joint publications, with particular involvement in the project guidance report; providing access to monitored sites and other site data.

Potential beneficiaries will have access to the results of the research through a programme of dissemination that will span both UK and international industry and government. Dissemination of scientific results will be carried out via publications in top international geotechnical and plant science journals, and articles will be published in wider readership journals and magazines. A final project guidance manual will be produced, outlining the scope and design of ideal soil-root systems.

Two workshops will be held, one at the start of the project, particularly to engage with new potential end users of the research, and the wider international community, and another towards the end of the project to disseminate results. Regular research updates and key outputs will be added to the project website, incorporating a RSS feed, and linked from appropriate academic websites and scientific/social media.
 
Description China Scholarship Council PhD Studentship
Amount £45,600 (GBP)
Organisation University of Leeds 
Department China Scholarship Council
Sector Academic/University
Country United Kingdom
Start 09/2017 
End 09/2020
 
Description Newton Advanced Fellowship (Overseas visiting - Prof. Likitlersuang)
Amount £71,945 (GBP)
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 11/2017 
End 11/2019
 
Title Use of geotechnical centrifuge for scaled testing of rooted slopes 
Description Development of scaling methods for testing rooted slopes in geotechnical centrifuge 
Type Of Material Improvements to research infrastructure 
Year Produced 2017 
Provided To Others? Yes  
Impact Young plants grown in centrifuge models of slopes were found to represent the mechanical reinforcement associated with mature root systems in the field. A paper was published describing the study and its implications for geotechnical centrifuge studies of root reinforcement. 
URL http://dx.doi.org/10.1016/j.ecoleng.2017.06.067
 
Title Analysis of coupled axial and lateral deformation of roots in soil - figure data 
Description This data archive is linked to the following publication: 'Analysis of coupled axial and lateral deformation of roots in soil' by G.J. Meijer, D. Muir Wood, J.A. Knappett, A.G. Bengough and T. Liang, as published in the International Journal for Analytical and Numerical Methods in Geomechanics (https://doi.org/10.1002/nag.2880). This data achieve contains all data required to replot any graph in this manuscript (Figures 8-18 and 20-22). Note that this paper is covered by a CC-BY license, see https://creativecommons.org/licenses/by/4.0/ 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
 
Description Assessing the Performance of Grass and Soil in Resisting Erosion - Phase 1 project with CH2M and Environment Agency 
Organisation CH2M HILL
Country United States 
Sector Private 
PI Contribution We are working with CH2M (Project Partner), having been invited by them to tender as subcontractors to this Environment Agency Phase 1 project, conerning the role of grass vegetation in resisting soil erosion of flood embankments.
Collaborator Contribution Working jointly to deliver recommendations for further measurement/monitoring of grassed flood embankments, in view of literature review in progress.
Impact Collaboration has just started.
Start Year 2017
 
Description 13th Geotechnique Lecture (ICE) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Dr Knappett was invited to give the 13th Biennial Geotechnique Lecture at the Institution of Civil Engineers, London, UK on 14 November 2017. The topic was "The use of vegetation in low carbon geotechnical engineering", and included a section talking about the Rooting for Sustainable Performance project. The audience was predominantly national (>100 in the lecture theatre), but was also live web-broadcast (and now archived online via the ICE's website) which reached internationally (>100 additional people were registered as watching online).
Year(s) Of Engagement Activity 2017
URL https://www.ice.org.uk/eventarchive/geotechnique-lecture-2017
 
Description Conference presentation at ALERT Geomaterials workshop 2019, 1st October 2019, Aussois, France 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited talk to conference by Dr G Meijer, continues to build on collaboration with Grenoble University
Year(s) Of Engagement Activity 2019
URL http://alertgeomaterials.eu/2019/02/alert-geomaterials-workshop-2019/
 
Description Friends of University of Dundee Botanic Gardens talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Talk to Friends of the University of Dundee Botanic Garden, and interested members of the general public, concerning Plants and Engineering.
Title: Carbon-friendly engineering of soil with plants.
Location: University of Dundee Botanic Gardens,
Date: 7 September 2018, Dundee.
Year(s) Of Engagement Activity 2018
URL https://www.dundee.ac.uk/botanic/news/2018/article/plants-and-engineering-with-dr-neil-paterson-and-...
 
Description Inaugural talk to public audience at University of Dundee "Discovery Days" event 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Approx 200 audience (combined general public, students and academics) attended, sparking considerable discussion and interest.
Year(s) Of Engagement Activity 2018
URL https://www.dundee.ac.uk/media/dundeewebsite/revealingresearch/documents/2018-Discovery-Days-Program...
 
Description International Society of Root Research Medal Lecture 2017 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The ISRR2017 medal lecture invites an eminent scientist who explores root-soil interactions to Dundee to present a lecture, preceded by talks and poster sessions by predominantly early career researchers. This year the invited speaker was Prof Michelle Watt from Juelich.
Year(s) Of Engagement Activity 2017
URL http://www.hutton.ac.uk/events/root-rhizosphere-workshop-and-2017-isrr-dundee-medal-lecture-root-res...
 
Description Invited joint keynote: 8th Plant Biomechanics International Conference. 30th November - 4th December 2015, Nagoya, Japan. (invited keynote) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Dupuy L and Bengough AG. 2015. Keynote paper presented by Dupuy "Physical factors affecting root growth and interactions with the soil environment. "
Year(s) Of Engagement Activity 2015
 
Description Invited participation in 25th New Phytologist Workshop (at Sommieres, France) on root traits as predictors of plant-soil functions 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Approximately 20 international scientists (mainly Europe and USA) invited to the 25th New Phytologist Workshop looking at functional interactions between root ecological traits and soil/ecosystem functions. A special topic chosen at the meeting was to focus on soil stabilisation as an important root trait function, and Alexia Stokes and helped to lead a session on this topic.
Year(s) Of Engagement Activity 2019
URL https://www.newphytologist.org/workshops/25
 
Description Invited seminar at University of Grenoble, September 2019 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact Invited seminar by G Bengough to Grenoble Geotechnical Engineering department, collaboration with joint PhD student is ongoing...
Year(s) Of Engagement Activity 2019
 
Description Invited seminar to ETH Zurich 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Prof Paul Hallett provided a talk on how soil structure interacts with plants. This drew on both agronomic and engineering applications.
Year(s) Of Engagement Activity 2015
 
Description Keynote lecture at international workshop in Barcelona 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited keynote by G Bengough at international workshop. September 19-20, Barcelona, Spain. Approx 45 participants.
Year(s) Of Engagement Activity 2019
URL https://congress.cimne.com/MUSLOC2019/frontal/default.asp
 
Description NERC Planet Earth Article 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Article in the NERC Planet Earth magazine, written by journalist Julia Horton. This covered a range of projects conducted by University of Aberdeen scientists on tropical agriculture. The work draws on both our direct research in tropical countries and strategic research on plant-soil interactions, so it cuts across P. Hallett's funding portfolio.
Year(s) Of Engagement Activity 2017
URL http://www.nerc.ac.uk/planetearth/stories/1879/
 
Description Presentation for Interdisciplinary Plant Group (University of Missouri, Columbia USA) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited presentation to approx 200 participants of 34th Annual IPG meeting at University of Missouri, Columbia concerning biophysics of root-soil interactions.
Year(s) Of Engagement Activity 2017
URL https://ipg.missouri.edu/feature-stories/34thAnnu_07012017.cfm
 
Description Presentation to Annual Hutton Symposium 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact 300 plant and environmental scientists attended meeting to discuss research activities associated with The James Hutton Institute. Talk prompted new collaboration.
Year(s) Of Engagement Activity 2017
 
Description Repeat of 13th Geoetchnique Lecture for ICE Scottish Geotechnical Group 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact This was a repeat (with some updating of results of ongoing work) of the 13th Geotechnique Lecture (see separate entry) as part of the ICE Scottish Geotechnical Group evening seminar series. The title of the lecture was "The use of vegetation in low-carbon geotechnical engineering". See separate entry for further details.
Year(s) Of Engagement Activity 2018
 
Description Root-soil/slope Workshop and ISRR Medal Lecture in Root Research (2016) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Meeting on root-slope interactions, designed to engage with both practitioners (including members of our EPSRC Project Advisory Group), postgraduate students, and researchers.
Year(s) Of Engagement Activity 2016
URL https://roots-dundee.eventbrite.com
 
Description Workshop on grass reinforcement of floodbanks 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Stakeholder meeting with approx 40 attendees to discuss problems of grass erosion on floodbanks. Purpose was to refine and develop business case options for potential project with Environment Agency on improving the use of grass on floodbanks in the UK.
Year(s) Of Engagement Activity 2018
URL http://evidence.environment-agency.gov.uk/FCERM/en/Default/FCRM/Project.aspx?ProjectID=A4D87116-F4D3...