Murphy Geospatial Monitoring Department was approached by long-standing client, Joseph Gallagher Limited, to assist them in providing a monitoring solution for a section of track in Croydon, South East London. JGL were undertaking a sizeable undertrack crossing using micro tunnel boring techniques to install services for the utility sector.
Murphy Geospatial put forward a track monitoring system consisting of a chain of precise wireless tri-axial tilt sensors which would be affixed directly to the track and sleepers. Along with the tilt sensors, Murphy Geospatial installed an accurate manual monitoring network consisting of reference targets installed outside the zone of influence of the works as well as ‘backup’ monitoring targets alongside the tilt sensors.
When working on rail, access is always an issue and a risk to our teams. We worked closely with our client and TfL to gain safe and secure access to the tramline to ensure we could install our tilt monitoring system and manual monitoring targets within the tight timeframes. Our client was very happy with our quick approach which allowed them to complete their works on time with no disruption to the live tram service.
Track gauge and cant (crossfall of the track) were recorded at each array or section where the sensors were placed, and a baseline reading for the track position and geometry was recorded. In addition, baseline readings were taken for the monitoring targets in the unlikely event that a tilt sensor should become damaged or dislodged. This allows Murphy Geospatial to return to site and carry out a manual reading to ensure no movement of the track has occurred.
We deployed a team of engineers for the installation and setup of the tilt sensors and manual monitoring network. We then scheduled regular visits for our survey team to carry out the manual checks at the required intervals. Our monitoring team are well-versed in the rail environment and have many years experience working in the fast-moving industry.
The output of the ongoing monitoring was that of two-fold. The monitoring data was collected by the automated system of tilt sensors as well as using the total station with a surveyor at the controls.
Figure 1 – Results from the automated tilt sensors affixed to the track; the green line at the extents of the graph is the green trigger threshold.
Figure 2 – Results from the manual monitoring surveys carried out on site. The fluctuations in data are the result of the accuracy of the total station (+/- 2mm).
For more information on this project, please contact Andrew Masters at firstname.lastname@example.org or +44 203 598 3775