Fibre Optic Rock Bolts for strain and shear monitoring

Over the life of an excavation, rock movements may transition from distributed to discrete as cracks and shear zone localise. As such it is important to accurately monitor the strain profile of fully grouted rock bolts.

By monitoring a rock bolt’s strain profile much can be learned and ascertained about the behavior of the rock mass.



Stress and strain monitoring

The fibre optic rock bolts supplied by Geosystems can be installed using standard methods. Once in place, the Fibre Optic Bolts can be connected to an optical analyser (which can be located hundreds of meters away). The analyser will provide data on the strain profile. This solution is particularly powerful for coal mining applications where the analyser can be placed in a safe zone quite distant from sensors. The fibre bolts can detect shear which makes them very unique and useful, the fibre analyser and cable enable very close spacings between data points resulting in high-resolution coverage along the bolt length, this is critical for detecting shear and virtually impossible with alternative electrical technologies. Both axial/longitudinal and shear influences on the bolts will be detected.

Geosystems’ Fibre Optic Rock Bolts provide the perfect solution to monitoring the strain profile of fully grouted rock bolts.

Rock Bolt Features:

  • Suitable for both rock mines and coal mines
  • Inherently safe and IS certifiable optical rock bolts
  • Measurement of strain profile rather than localized strains
  • Spatial resolution from 5cm down to 1mm
  • Operational accuracy better than +/- 10 microstrains
  • Instrumented optical bolt cost minimized
  • Suitable to a variety of rock bolts : rebar, threadbar, NMX, CT, AT & AX grade bolts
  • Clusters of bolts can be monitored simultaneously
  • Autonomous monitoring
  • Networking ready
  • Data plentiful and accessed remotely in real-time.

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