Tunnel Profile Monitoring System

Geonor, Inc - Precision Instrumentation


The RST Tunnel Profile Monitoring System is a series of linked rods, fixed to the tunnel wall, to monitor deformation. A data logging system and related software is available to provide near real time displacement and generate a graphical representation of tunnel performance.

A system of linked arms is affixed to the tunnel wall. Each arm is fitted with a high accuracy displacement sensor and precision tilt meter. Spatial displacement of the pins and arms results in changed tilt and displacement readings. The data logger system automatically collects the data and transmits it to a computer. The computer then analyzes the data, and calculates the displacement profile for presentation.

The system is available in either open or closed loop configurations. The closed loop method is analogous to conventional closed end survey techniques, while the open loop must be referenced to a known location.


  • Low profile design, with multiple arms that fit close to the tunnel wall and may be bent in the field to accommodate obstructions on the tunnel wall.
  • No tunnel traffic interference.
  • High system accuracy of up to 0.06 mm of deformation.
  • Custom engineered by RST to suit each individual application.
  • Built in connectors for manual tape extensometer connection to verify operation, and aid in initial installation and commissioning.
  • Integral multi stage transient lightning protection.
  • Immune to the air density related problems inherent in optical systems.
  • On board electronics to minimize electrical noise problems, and permit tilt sensor calibration independent of cable length effects. Cable length may be changed without affecting sensor calibration.
  • GeoViewer near-real time software with full graphic and alarm capability.
  • Direct measurement of displacement, rather than calculating displacement from a tilt measurement.
  • Digital Bussed System: single cable per arm to simplify installation and reduce cost.


  • Monitor underground openings during construction for control and safety.
  • Monitor tunnel deformation due to nearby construction activities.
  • Monitoring long term deformation and performance of existing tunnels.


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