Two Decades’ Worth of Lessons Learned from the Use of Distributed Fiber Optics for Ground Characterization and with Tunneling

Over the past two decades, the author along with his research group and industrial partner began to develop a novel Rayleigh-based distributed optical strain sensing technology capable of monitoring strain along a ground support scheme at sub-centimeter spatial resolution. This came out of the requirement to monitor and understand the geomechanics of composite ground support systems at the micro-scale. This line of research has been extended to monitor fully grouted rock bolts (FGRB) and rock mass deformation with an increased resolution of sub-millimeter spacing (0.65 mm). This distributed optical sensing technique has been tested in the laboratory and been implemented at multiple sites around the world. Within this context, this paper summarizes key lessons learned (i.e., spatial resolution, QA & QC, and industrial applications) over the past two decades regarding the use of fiber optics for monitoring the ground conditions and support elements in underground excavations. Through such monitoring, the goal is to improve current design and guidelines.