Geophysical Condition Assessment of Railway Earthworks (GEO-CARE)

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.

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.