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Victoria Station - Track Monitoring

CLIENT: London Underground / TWBN

How the flexibility and mobility of FlatMesh™ enabled a grouting team to stabilise ground below London Underground tunnel at Victoria Station without damage to track

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Victoria Station Upgrade Project

Challenge

The upgrade to London’s Victoria Railway Station was a large and complex undertaking. As part of the project, an underpass had to be tunnelled directly beneath a shallow brick-lined tunnel carrying the District and Circle Line. In order to stabilise the permeable ground before the tunnelling took place it was treated using the TAM grouting process. The work had to be conducted during short Engineering Hours access windows. In order to manage the risk of ground heave damaging the tracks, the client required a real-time, high-precision monitoring solution that could be quickly deployed during each shift. Optical methods were rejected because lines of sight could not be guaranteed. Wired monitoring systems were also rejected because they would have been prone to damage and would have been slow to deploy. A wireless monitoring solution using the Sencieve FlatMesh platform was selected.

Solution

During grouting, movement could occur in any part of the 30 metre zone across two separate tracks. TWBN employed Senceive’s patented and specially upgraded magnetic mountings to secure the 20 wireless sensors directly onto  the  surface  of  the  rail. Using the highly responsive FlatMesh™ wireless communications platform the system was operational within a few minutes of installation at the start of each shift.   It was able to report any movement in excess of 0.009 degrees of angular tilt.  Reporting frequency was set at no more than one minute. All this was carried out without signal or power cables.

Outcome

The sensors communicated in real-time to a gateway attached to a laptop computer on the site. For this project, functionality was added to ensure that clear visual alerts and audible alarms would be triggered by any movement above pre-set trigger levels. This meant that the computer did not have to be permanently manned, allowing the engineer responsible for monitoring to complete other tasks.

The data were characterised by a  high level of stability throughout the grouting programme. The small  levels of movement that were identified were corroborated by levelling surveys. No false alarms were raised.

This unique use of Senceive’s award-winning tunnel and rail-focused technology was installed on site within three weeks of the initial proposal.  Senceive specialists worked alongside shift engineers for the first two nights, to ensure all was well and the system was fully understood. After that, the monitoring was exclusively carried out by TWBN engineers who were extremely pleased with its overall performance and benefits.

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Key Points

  • Installed and removed for every night shift
  • Operated by non-specialists
  • Sub-minute reporting intervals
  • Reliable, precise measurement of movement enabled ground stabilisation team to operate with confidence.