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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

The project involved converting an existing listed building originally built as a coaching house into modern London premises that included a sublevel swimming pool, gymnasium and garage (accessed by lift). The construction work involved forming a basement under the whole plot, while retaining most of the built structure above the excavation at ground level. To prevent damage to surrounding buildings and support the excavation, a propped diaphragm wall was constructed.

The monitoring contract, part designed by CMCS, consisted of:

• Monitoring continuously horizontal movement profiles at selected locations around the diaphragm wall. Warn automatically if threshold levels were reached so that remedial action could be taken.
• Measurement of the load in selected props used to support the diaphragm wall, similar warning as above.
• Measurement of the shear strains imposed on existing brick walls terminated at ground level while their foundations were undermined by the excavation beneath.
• Weekly checks on movements of the diaphragm walls using manual surveys (carried out by CMCS).
• Total station surveys at specified times through the contract by an independent survey company, or as indicated by the automatic monitoring.
• Automatic alarms of any parameters exceeding pre-determined levels.
• Remote data retrieval by the consulting engineers (at four remote locations).
• On site display of data so that any actions required to control movements could be carried out by on site personnel immediately, i.e. increasing jacking loads on the supporting props to reduce inward movement of the diaphragm wall.

Diaphragm wall measurements were made using electro-levels solidly cast into the wall - an installation technique unique to CMCS. Prop loads were monitored using vibrating strain gauges. Currently CMCS use radio-logging systems so that cabling is kept to a minimum. The electro-levels are capable of detecting movements of the piles of less than 1mm from initial zero readings, 12 months earlier.

The data from the system was available on line to the consultants as well as on site for the contractor to take instant action if required to safeguard the project. An example of the computer display screen is given above. The boxes containing the data changed colour if any of the data they represented exceeded safe threshold levels. Clicking on any of the boxes calls up time plotting routines for that instrument.

The photographs (above, right and below) show how congested a redevelopment site can become during the construction process.

The photograph (right) shows a CMCS radio transmitter used on a large, also congested, site at White City, London. The advantage of using radio is two fold:

1. It eliminates the risk of other site operatives cutting vulnerable cables and
2. Installation is made easier.