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1. Index
2. CMCS at BRE
3. Development of AMS
4. Non-destructive testing of Marine Jetties
5. Fixed sensor monitoring of Diaphragm walls
6. Monitoring Buildings during Redevelopment
7. Tunnel Monitoring
8. Embankment Systems
9. Loggers
10. Tunnel Distortion Monitoring
11. In-place tilt monitoring system
12. Tunnels Interaction System
13. Re-Development of Small Properties
14. Viaducts
15. DLR at Mansion House
16. Tunnel Monitoring System (Discrete beams)
17. CTRL 240
18. Dams
19. Electro-levels
20. Movement indicators
21. Results of Charing Cross Load Cells
22. Non-destructive testing of concrete structures
23. Radio in Construction Monitoring
24. Settlement Reducing Piles
25. Land Surveying and Total Station Monitoring
26. Vibration Monitoring
27. Monitoring the complete strain history of concrete elements
28. Past CMCS Projects

CMCS in conjunction with Fugro install CMCS monitoring equipment in the London Underground Limited (LUL) Central Line of tunnels at Stratford. The monitoring equipment was installed to safeguard the normal operation of the Central Line trains during the construction of two 8 m diameter main line railway tunnels for the new Channel Tunnel Rail Link (CTRL) from Stratford into Central London. The new tunnels pass under the LUL tunnels within 100 m of leaving the launching box, see photograph (below).

Due to the stiffness of the tunnels concerns were expressed that the expected ground movements would crack the tunnel linings. Circumferential bolts were loosened at intervals along the axis of the tunnels, thereby converting them into a series of articulated sections, between 3 and 10 m long, within the zone of influence of the CTRL tunnels. Both the East and West bound LUL tunnels were fitted with arrays of electro-levels to monitor changes in deflection, rotation, twist and shear of the articulated sections. In addition linear movement transducers were fitted to monitor axial movements between the articulated sections.

Data from the instruments were recorded by CMCS loggers and transferred via GSM modem to both the CTRL site control office and LUL offices. CMCS software displayed the large volume of data in a relatively easy to understand format on site computers as well as warn on call engineers via mobile phones if set limits in the data were exceeded.

Details showing the relative positions of the CTRL tunnels are shown in the diagrams below.

The section (above left) shows the relative distances between the new CTRL tunnels and the existing LUL Central line tunnels. The tunnel monitoring systems was installed within a 5 week period along side other activities taking place in the LUL tunnels. Despite the relatively short space of time the system was operational in sufficient time to allow the first of the CTRL tunnels to pass under the LUL tunnels before the Christmas 2003 break.

LUL engineers satisfied with the stability, resolution of the system and software display allowed the TBM to under their tunnels.

During the critical stage of the first drive under the Eastbound tunnel CMCS engineers were on site to respond instantly to any problems. There were no problems, the information from the electro-levels showing the movement of the tunnel long before the precise surveys carried out during engineering hours confirmed the magnitudes that occurred.

Comments from both LUL and the London Bridge Associates (consultants for the project) were extremely complimentary to the performance of the monitoring system and CMCS's response during the initial phase of the work. CMCS were not needed on site during the driving of the second CTRL tunnel, but were contactable by telephone to give advice.