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.


  • 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


  • 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)



Markus Stolz

Civil Engineer

Member of the extended executive board
Division manager geotechnics /
Geotechnical instrumentation and measurements / hiDCon

T 0041 44 806 29 41

Médéric Piedevache

Engineering Geologist ENSG

Member of the extended executive board
Branch manager Nancy, France

T 0033 3 83 94 04 50

Holger Wörsching

Civil Engineer

Member of the extended executive board
Division manager geotechnics /
Development of measuring systems / TDR probes /
Geotechnical instrumentation and measurements

T 0041 44 806 29 43

Dr. Sebastian Brenne


Project Manager

T 0049 234 904 4717