The Profile Monitoring System for Tunnel Concrete Segments is a series of tilt meters, fixed to the tunnel wall on each of the precast concrete segments erected in place as tunnel lining by a Tunnel Boring Machine (TBM). This Profile Monitoring System using tiltmeters is a simplified version of the Tunnel Profile Monitoring System and its main advantage is that it can be deployed in the tight space available around the TBM, whereas the Tunnel Profile Monitoring System would be much more difficult to install in the same situation to monitor deformation. A data logging system and Geoviewer software are available to provide near real time displacement and generate a graphical representation of the tunnel. The system is based on the assumption that each concrete segment is a rigid body and that the complete ring deforms by rotation of the individual segments one relative to the other, and the rotation points are the contact surfaces between adjacent segments. This assumption is very often considered as acceptable by tunnel designers and reasonably close to reality, although spot checks using traditional convergence measurements or surveying methods should be conducted to confirm its validity for each individual tunneling circumstances.
Range: ±15° (other ranges upon request)
Resolution: ±2 arc sec. (±0.0006°) (0.01 mm/m)
Non-linearity: ±0.0125% F.S. (±0.002°) (0.03 mm/m)
Repeatability: ±0.0125% F.S. (±0.002°) (0.03 mm/m)
System Accuracy: 1 mm convergence typical
Sensor: MEMS (Micro-Electro-Mechanical Systems) Accelerometer,
Operating Temp.: -40 to 85°C

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