http://lunainc.com/hd-fos-safer-stable-excavations-tunnels/
Tunnels and other underground excavations
typically require some form of ground support or reinforcement to increase the
stability of the excavation and improve safety. This support system often takes
the form of a combination of support components, such as rock bolts, tendons,
umbrella arches and forepoles.
Monitoring these
ground support components could potentially provide valuable information in
assessing the performance of the support system, as well as detecting ground
movement around the excavation. Unfortunately, traditional monitoring
approaches have provided only very coarse data and limited insight. Therefore,
a research team at the Geological Sciences and Geological Engineering
Department at Queens
University
The team evaluated
multiple fiber optic sensing technologies, and concluded that fiber optic
sensing based on the Rayleigh backscatter mechanism and measured using OFDR
techniques, otherwise known as high-definition fiber optic sensing (HD-FOS),
provided the best combination of capabilities for this application. In
particular, the low cost of HD-FOS sensors and the their sub-millimeter
resolution, which opens up the ability to both capture and identify local and
micro-scale ground support phenomena, were deemed as the most important
advantages.
The research team evaluated and verified the performance of standard
HD-FOS sensors directly coupled to ground support components in multiple tests
using Luna’s ODiSI measurement system for HD-FOS.
You can read all the details of the team’s work and conclusions in the paper
“The Application of Distributed Optical Strain Sensing to Measure the Strain
Distribution of Ground Support Members” available online here
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