Geophysical Condition Assessment of Railway Earthworks (GEO-CARE)

Lead Research Organisation: Queen's University of Belfast
Department Name: Sch Planning Architecture and Civil Eng

Abstract

Many parts of the UK's rail network were constructed in the mid-19th century long before the advent of modern construction standards. A recent study conducted by Network Rail, who own the largest network of earth structures in the UK, has revealed that 50% (5000km) of their network of earthworks are considered to be in a "poor" or "marginal" condition thereby necessitating significant maintenance. With the expected changes to the UK's precipitation patterns over the next 70 years likely to have a significant effect on railway earthworks, it is crucial that appropriate approaches for assessment of their stability are developed, so that repair work can be better targeted and failures avoided wherever possible. The consequence of failures of major infrastructure elements is severe and can include loss of life, significant replacement costs, line closures and major disruption to services which can often last for several months. Advance assessment and remediation of earthworks is always significantly less costly than dealing with failures reactively.
The aim of this project is to investigate the potential use of a rapid, cost effective and non-destructive approach for assessing earthworks at risk of failure. This involves an investigation into the sensitivity of a recently developed geophysical method, the Multichannel Analysis of Surface Waves (MASW), for measuring variations in fluid induced pressure changes, resulting from rainfall. This potentially provides a practical and relatively robust means of assessing the stability of earthworks. Despite the advantages that the MASW method provides, it has not been tested previously for assessing fluid induced changes in slopes or earthworks. Therefore, from the point of view of scientific timing, an opportunity currently exists to explore the novelty of this application. The importance of this opportunity is highlighted further when consideration is given to the current and future industrial needs to improve assessment of earthworks as a result of climate variability.

Planned Impact

A range of economic, societal and academic impacts will be accrued during and long after the completion of this project, the aim of which is to develop a means of assessing infrastructural earthworks at risk of failure. The consequence of failures of major infrastructural elements is severe and can include loss of life, significant replacement costs, line closures and major disruption to services. Each of these consequences may have serious societal and economic implications. In addition to the obvious safety hazard presented by infrastructural failures, quality of life may be significantly impaired as a result of line closures and service disruption, for example by increasing commuting times for rail passengers. Failure of one part of an integrated transportation network can have serious consequences for the effectiveness of other parts, with any spare capacity quickly becoming saturated and then the entire network overloaded. For example, a single railway earthwork failure may lead to serious increases in road traffic and journey times as commuters are forced to use alternative forms of transportation. The economic consequences of earthwork failures are also considerable. According to Department for Transport the annual average Network Rail spend on earthworks for the period 2004/5 to 2008/9 was £83 million, with an average of 65 earthwork failures per year recorded during this period. Network Rail have recently revealed that 50% (5000km) of their network of earthworks are in "poor" or "marginal" condition, thus requiring excessive and expensive maintenance.
Advance assessment and remediation of earthworks is significantly less costly (societally and economically) than dealing with failures reactively. As such, one of the main objectives of this project is to develop a rapid, cost effective and non-invasive means of assessing the stability of earthworks using seismic surface waves. From the point of view of academic impact, an opportunity currently exists to explore the novelty of this application. The importance of this opportunity is highlighted further when the potential effects of expected increased rainfall and more frequent extreme weather associated with climate change are considered.
Although the project will focus on railway earthworks due to their generally poor condition, the proposed approach also applies to other forms of earthwork construction (e.g. for roads and waterways) and for natural slopes. It is intended that in future we will widen our focus to investigate these areas. This proposal also responds to the call in the UK government's National Infrastructure Plan of 2010, for "maximising the potential of existing road and rail networks". This clearly requires knowledge of how to cost-effectively assess and maintain infrastructure.
Beyond the societal and economic costs that this project will potentially impact, organisations receiving immediate benefits from the development of an approach to assess earthworks include those responsible for earthwork maintenance such as, Network Rail, Highways Agency and British Waterways, all of whom have written letters of support for this project. Commercial geophysical and geotechnical companies will also benefit from development of a novel application and methodology for surface wave geophysical testing. In particular, the UK based companies, Zetica Ltd. and In-Situ Site Investigation Ltd., who will provide support for this work, will benefit from their link to the project, as all publications and presentations arising from this research will acknowledge their contribution.
The training of the post-doctoral research officer to be employed on this project also comprises an important impact. In addition to the impact that this project will have on the individual's career development, the skills and knowledge gained throughout this process will benefit their future employers and, depending on their future career path, potentially society in general.
 
Description GEOphysical Condition Assessment of Railway Earthworks (GEOCARE) has produced the following key findings:
1) A suitable methodology has been developed for rapid and non-invasive 2D acquisition and processing of seismic data for assessment of railway earthwork condition. This methodology is based on the Surface Waves (SW) geophysical approach.

2) This project has demonstrated that reliable, time-lapse seismic datasets of the near surface may be obtained using the SW approach. The relevance of the observed time-lapse variations were verified with respect to the experimental data uncertainties.

3) It has been shown that this approach is capable of portraying temporal fluid induced geotechnical property variations in partially saturated earthworks in a field setting. Consistent spatial and temporal variations for these data were observed on an unstable railway earthwork, with an increase of Rayleigh velocities in the spring-summer months, and vice versa lower velocities recorded during the autumn-winter period. This temporal trend correlates well with the precipitation pattern, soil water content and pore water pressure data measured at the test site.

4) The results obtained in terms of acquisition and processing of MASW data, are particularly relevant from an engineering point of view, as they demonstrate the potential of this non-invasive, time and cost-effective approach for time-lapse monitoring of climate induced geo-mechanical property variations of railway earthworks at risk of failure.
Exploitation Route Geophysical researchers will benefit from the novel approach developed for assessing fluid induced changes in slopes or earthworks. Researchers from Japan and France, for example, have already tested our methodology and published comparative findings. Although the project focused on railway earthworks due to their generally poor condition, geotechnical, geological and transportation researchers may be interested in applying the approach to other forms of earthwork construction (e.g. for roads and waterways) and unstable natural slopes.
A recent project, funded by NERC (Seismic imaging for improving flood defence management, NE/R008884/1) aims to translate the findings of GEOCARE, to managers of water retaining earthworks that protect large areas of the UK from flooding. This project aims to enable our partners (Environment Agency, Canal & River Trust, Northern Ireland Water), to diagnose the internal condition of their geotechnical assets using a non-invasive geophysical approach. This will allow our partners to establish proactive (rather than responsive) intervention strategies, and to introduce adaptive solutions to improve asset drainage and stiffness, thereby increasing the resilience of the UK's critical water retaining infrastructure to future climate variations.
Sectors Construction,Environment,Culture, Heritage, Museums and Collections,Transport

 
Description International geophysical consultancies have recently started using the adopted methodology for time lapse subsurface monitoring of geotechnical properties. The approach was also used to assess climate effects on the stability of a natural slope beside a road operated by Transport NI. Landslides are a common occurrence on this particular stretch of road on the Northeast coast of Co. Antrim. Road closures caused by mudflows have societal impact, resulting in increases to road traffic and journey times as commuters are forced to use alternative routes or forms of transportation. Queen's University Belfast hosted the 6th international workshop on Civil Structural Health Monitoring (CSHM-6) in conjunction with the International Society for Structural Health Monitoring of Intelligent Infrastructure (ISHMII) in May 2016 (weblink:https://www.qub.ac.uk/sites/CSHM-6/). As part of this event Dr. S. Donohue hosted a session on "Geotechnical monitoring of civil infrastructure to extend life and improve safety". This provided an excellent opportunity to disseminate the outcomes and recommendations from GEOCARE to an combined industry/academic audience. Recent work funded by the QUB EPSRC Impact Acceleration Account has enabled the technology to be showcased to the Environment Agency who are interested in employing it at along their network of flood defenses. As part of this work, in January 2017 an MASW survey of a section of the River Thames flood defence network (at the Hadleigh Marshes, near Southend) was carried out (in conjunction with EA and Team2100). In 2017, NERC provided funding, under the Environmental Risks to Infrastructure Innovation (ERIIP) scheme to assist with further translation of the research to a number of UK asset owners of water retaining earthworks. These included the Environment Agency, Northern Ireland Water and the Canal and River Trust. This project commenced in November 2017. With further research and industrial engagement it is anticipated that additional societal and economic impacts will be produced as the technology becomes implemented into asset owner monitoring systems.
First Year Of Impact 2015
Sector Environment,Transport,Other
Impact Types Societal,Economic

 
Description EPSRC Impact Acceleration Account (QUB)
Amount £24,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 01/2017 
End 03/2017
 
Description Environmental Risks to Infrastructure Innovation (ERIIP) Scheme
Amount £140,999 (GBP)
Funding ID NE/R008884/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 11/2017 
End 02/2019
 
Description Fusion
Amount £31,000 (GBP)
Organisation InterTradeIreland 
Sector Private
Country United Kingdom
Start 04/2016 
End 03/2017
 
Description BGS 
Organisation British Geological Survey
Country United Kingdom 
Sector Academic/University 
PI Contribution Development of test site, monitoring of seismic data, installation of field sensors, publication of papers, chairing project meetings
Collaborator Contribution Monitoring of resistivity data, installation of further field sensors, publication of papers, attendance at project meetings
Impact Bergamo, P., Dashwood, B., Uhlemann, S., Chambers, J., Gunn, D.A. and Donohue, S. (2016). Time-lapse monitoring of climate effects on earthworks using surface waves. Geophysics 81 (2), DOI: 10.1190/GEO2015-0275.1 Bergamo, P., Dashwood, B., Uhlemann, S., Chambers, J., Gunn, D.A. and Donohue, S. (2016). Time-lapse monitoring of fluid induced geophysical property variations within an unstable earthwork using p-wave refraction. Geophysics, In Press. Bergamo, P., Donohue, S., Gunn, D.A., Dashwood, B., Uhlemann, S., Chambers, J., and Ward, D. (2015). Time-lapse Monitoring of the Slopes of a Heritage Earthwork by Means of Near-surface Seismic Technique. Near Surface Geoscience 2015 - 21st European Meeting of Environmental and Engineering Geophysics, Turin. DOI: 10.3997/2214-4609.201413717 Gunn, D.A., Donohue, S., Dashwood, B., Bergamo, P., Rains, M., Uhlemann, S., Chambers, J. (2015). Earthworks ground model development using surface wave surveys. Investigation, Classification, Testing, and Forensics, ICE publishing. XVI European Conference on Soil Mechanics and Geotechnical Engineering, Edinburgh. DOI: 10.1680/ecsmge.60678.vol6.556 Gunn. D.A., Dashwood, B., Williams, G., White, J., Raines, M., Donohue, S. and Bergamo, P. (2015). Ground models for assessing seismic wave propagation in the shallow subsurface. Proceedings of the 13th International Conference on Railway Engineering, Edinburgh. Donohue, S., Bergamo, P., Hughes, E., Gunn, D.A., Dashwood, B., Uhlemann, S., Chambers, J., and Ward, D. (2014). Assessing climate effects on railway earthworks using MASW. Near Surface Geoscience 2014 - 20th European Meeting of Environmental and Engineering, Athens. DOI: 10.3997/2214-4609.20141995
Start Year 2013