The Role of Geophysics in Railway Asset Management
08 November 2004 16:02
Aperio director Simon Brightwell considers the trend toward using non-destructive and geophysical surveys on a network scale to provide rail engineers with objective knowledge of the construction, condition and value of their assets. This approach is especially relevant on the railways, where Network Rail and their overseas counterparts are moving more towards machine based data.
Geophysical and non-destructive surveys are still relative newcomers to the engineering world. For most of their, give or take 15 years, lifetime they have been used at specific sites to investigate specific problems. Things are changing, however: as the technology is maturing and is becoming more accepted, it is being used to provide information on a much bigger scale. Aperio’s clients are not just asking for site-specific information but also want an overview of the asset to provide knowledge of its construction using objective and repeatable measures that can be compared across the entire network. This knowledge can then be used to save time and money by targeting resources to where they are most needed.
The Rail Context
Simon Brightwell believes that Aperio are doing their job best when they are assimilating a vast bundle of information (such as ground penetrating radar files, network referencing data, and records such as cores and trial holes), and reducing this information to a neat tidy package that transfers knowledge to the client quickly and efficiently. Simon Brightwell has seen shelves groaning under the weight of hard copy reports from GPR trackbed surveys. This is the antithesis of what they are about, because in that form the information is useful to one person at one time and is unlikely to be re-used.
A recent innovation that provides a better alternative is viewing the Aperio GPR data through the OmniSurveyor3D package provided to UK rail clients by Omnicom Engineering Limited. Omnicom Engineering have the contract for an annual video survey of the UK rail network that is delivered to more then 800 users in Network Rail through a server-based solution. The data is viewed in a powerful software package that not only shows the track and other infrastructure from numerous camera views, but comes with tools to measure distances to millimetre accuracy and superimpose virtual objects such as new signal positions. This enables engineers to effectively ‘visit’ any part of the track without leaving their desk and view everything above the ground.
As the OmniSurveyor3D system records an accurate 3D profile of infrastructure it is also possible to import other geographically positioned data sets onto the video. Aperio and Omnicom Engineering have developed a means of viewing the thickness and condition of the trackbed either as a continuous thickness profile or as a colour wash painted onto the track video, providing the user with the visual comparison of conditions above and below the surface. The user can now define high or low thresholds in the data and look for exceptions such as ballast deeper than 700mm that could indicate settlement, or patches at risk of intermixing or forming ‘wet beds’.
For the Aperio data to be useful in OmniSurveyor3D, or used alongside any other track geometry data collected from the numerous survey trains, the process needs to be repeatable and the output needs to be a numerical string. The Aperio development team have therefore come up with a five-point condition index where a rating of one represents apparently clean ballast with a well-defined boundary with the materials below, and a rating of five represents ballast contaminated with fines or water. The algorithm analyses the amplitude of the radar reflections and reports results in a simple green/red colour scale.
This is just one example of how Aperio have refined the process from an artform to an objective science with repeatable methods and outcomes and this gives some interesting possibilities in terms of asset management. It is now feasible to repeat surveys of trackbed over, say, an annual cycle to look at condition trends and the influence of maintenance works. This approach is not limited to what lies below the rails however. Tunnel inspections are currently based on visual inspection and tactile testing (a rather elaborate description of hitting the brickwork with a piece of metal). Whilst there are access challenges such as getting around the overhead electrification, it is quite feasible to monitor the subsurface condition of a tunnel over a period of years more objectively using GPR.
A recent survey of the 51 masonry tunnels in Network Rail’s Western Territory to map unrecorded construction shafts provides another example of linking the geophysical data to the asset management strategy (in this case Network Rail’s Tunnel Management Strategy or TMS). Having analysed the GPR data for evidence of shafts, Aperio compared their results with historical and visual data and gave each result a confidence rating based on consistent inputs across the entire territory. Network Rail client Phil Roderick is keen on this approach. He said: “The methodology of applying a universal confidence rating to data gives us consistency across the 51 tunnels to further guide our hand in prioritising subsequent work. We have a good idea of where we should be devoting resources and digging holes, and in what order or priority. Aperio’s solution has been very successful and has given us value for money”.
Whilst Aperio expect to still be surveying individual sites to answer individual questions for many years, they do believe that their future lies in providing clients with results that are sufficiently robust, repeatable and well referenced to feed into asset management plans that will project 20 to 30 years into the future.
For more information on this company:
Aperio - Geophysical and Non-Destructive Surveys
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