Reverse Head Extensometer / Chain Extensometer
With the Reverse Head Extensometer, deformations can be continuously observed during excavation in front of the tunnel face or during the removal of slopes or the excavation of excavation pits. The modular design based on a chain of single extensometers provides a large number of measuring points in small diameter boreholes. The big advantage compared to other extrusion measuring systems is the continuous measurement of deformations during tunnelling or excavation. The manual readout of the stored measurements is done in a few minutes with a portable PC or PDA. The recording rate for the measured values of the individual displacement transducers is freely selectable.
Applications
- Tunnelling: monitoring of axial displacements at several measuring points in front of the working face for control and optimisation of the excavation support
- Embankments: Monitoring of displacements during the removal of slopes for permanent stability control.
- Excavation pits: Heave and settlement measurements during excavation of deep excavation pits
Specifications
- Minimum borehole diameter: 56 mm
- Number of measuring points: up to 16
- Distance between measuring points: > 0.5 m
- Installation length: max. 80 m
- Deformation distance: 100 / 250 mm per measuring point
- Recording rate: between 1 min and 24 h freely selectable
- Resolution: 0.01 mm
- Optional: temperature and pressure sensors
Instrumentation examples: Excavation pit Marienhof Munich and tunnel TELT (base tunnel Lyon Turin)
