Revolutionising the inspection of railway tenanted arches
Project challenges
Network Rail is responsible for maintaining viaducts supporting operational railway across the UK, which must be inspected at regular intervals to ensure these are safe to use.
Business challenge
Process Innovation
Sector
Road & Rail
Technology or capability
Metrology & NDT
Project Challenges
Network Rail is responsible for maintaining viaducts supporting operational railway across the UK, which must be inspected at regular intervals to ensure these are safe to use.
Many viaduct arches are commercially let and are therefore commonly termed tenanted arches. These tenanted arches are typically fitted with decorative cladding that obscuring the underlying brick-built arch structure. This however means the examine the structural integrity of arches, the mandated manual visual and tactile tap testing surveys requires the complete removal of the installed cladding as well as tenants’ fittings before an inspection, followed by reinstallation post-inspection.
There are several issues with the current process such as the removal and reinstatement of cladding being very slow and costly, as well as causing major disruption to tenants. Current examination processes are also subjective, lack high precision and require a skilled workforce. There is therefore a strong desire for a new inspection process that does not require the removal of cladding (i.e. inspect through it) that offers high accuracy and digital traceability.
MTC's Solution
MTC conducted a comprehensive review of all potentially suitable Non-Destructive Testing (NDT) technologies for the inspection of masonry arches through cladding. Through our downselection process, X-ray Backscatter (XBS) and Ground Penetrating Radar (GPR) technologies were selected as the most appropriate solutions.
XBS was shown to be viable for imaging defects related to the surface of brickwork through plastic and metal cladding, such as fractures, spalling, missing mortar and calcite deposition. GPR was shown to be capable to detect sub-surface defects such as ring separation of brickwork and voiding.
The capability of these technologies has been demonstrated both within controller workshop trials as well as a series of realistic tenanted arch inspection trials, alongside the development of processes for the semi-automated identification and reporting of defects from the NDT systems. Future work to fully automate the NDT examination of tenanted arches is underway utilising robotics and machine learning approaches.
Firstly, this technology is seen as critical to how we deliver tenanted arch examinations as it has the potential to reduce the both the cost of tenanted arch examinations and overall examination time by reducing disruption to tenants and reduced enabling works. This will improve our examination compliance and asset understanding. Secondly, it may provide more repeatable, consistent and interpretable outputs than a traditional masonry arch examination which can be applied to all arches.
Colin Hall, Principal Engineer (Structures), Network Rail
The Outcome
- NDT being successfully used to identify a diverse range of surface and sub-surface defects from on-site trials in tenanted arches, establishing XBS and GPR performance for masonry examination with cladding in situ.
- Full technical specification developed for the integrated data acquisition, processing, and reporting.
- Up-skilling of current arch inspectors on the deployment of new NDT approaches as part of a wider process to adopt the technology within the industry.
Benefits to the Client
- XBS and GPR examination can be conducted with cladding in place, enabling inspection of tenanted arches on schedule, with minimal disruption to tenants and reduced costs.
- Full data traceability between inspections allows for enhanced understanding of the condition of tenanted arches and could help inform predictive maintenance approaches.
- These technologies enable objective characterisation and measurement of defects, with potential for automation of both data acquisition and processing that is currently being investigated by the MTC.
