26. Fiber Optics Sensing of Stressing and Fracture in Cylindrical Structures

The SCARC (Simulated Carbon Ash Retention Cylinder) model is being developed to model rock stressing, and fracture development, when underground ground voids are backfilled with mine wastes. SCARC specimens are hollow tubes, cast with cementitious materials, and are filled with different blends of mine wastes, such as tailing and post-processed slurry. To monitor the strain history of the concrete cylinder, fiber optical sensors are wrapped around the tube exteriors. This distributed fiber optic layout consists of eight FBG strain gages in a single loop, permanently affixed to the SCARC cylinder. The fiber optic sensors monitor the material expansion characteristics of the initial filling stage of the waste material, and perpetually monitor the induced strain over a 24 h period. The initial experiment, of SCARC specimens, indicates that fiber optic sensors can successfully monitor, and accurately report, the strain history of the cylinder, as well as detect the fracture location within the cylinder, by the distributed sensor array. The results indicate the potential of fiber optics as embedded sensors for monitoring the backfilling of waste into abandoned mines, which is suggested as a mine stabilization technology.