Monitoring of mining induced subsidence through measurement of ground strains with Fiber Bragg Grating sensors
In this paper the application of Fiber Bragg Grating based sensors for the monitoring of mining induced subsidence phenomena is illustrated. A high number of sensors were installed in the pavement of a major highway thanks to the use of Bragg Grating arrays encapsulated in composite rods. The sensors and the associated demodulation equipment provide continuous measurements and allow the immediate implementation of safety measures by the authorities responsible for the highway.
Fibre Optic Sensing Based Slope Crest Tension Crack Monitoring System for Surface Mines
The stability of slopes in surface mines is of high concern due to the risk to both personnel and excavation plant. A variety of slope stability monitoring systems have been developed and implemented in the industry in order to predict slope failures before they occur and to minimise the damage to peopleand plant. This paper examines the technical challenges of the current slope tension crack monitoringsystems and demonstrates the feasibility of an innovative FBG-based crack sensing system. The results of preliminary experiments show that with the application of the mechanical displacement converter, the slope crack generation can be measured using FBG strain sensors.
Degradation of graphite/bismaleimide laminates with multiple embedded fiber optic sensors
This paper summarizes the reduction in mechanical properties of graphite/bismaleimide (Gr/BMI) laminates due to the presence of multiple embedded fiber-optic sensors. Previous work has shown that small quantities of optical fibers embedded parallel to the loading direction have only a negligible effect on the tension behavior of laminated structures. This work establishes the significance of larger quantities of embedded optical fibers on the tensile and compressive behavior of composite laminates. Experimental strength and modulus data from six test groups of seven tension and seven compression specimens are compared to a control group. All specimens were fabricated from G40-600/5245C Gr/BMI pre-preg tape to form a [°3/9o2/°]s stacking sequence. The quantity of optical fibers embedded parallel to the loading direction was varied in the different test groups. Uniaxial compression testing using an IITRI fixture and uniaxial tension testing were performed in accordance with ASTM Standards. Catastrophic failure was induced by fiber fracture. Results indicate that large quantities of embedded optical fibers reduce the static tensile strength up to 4% and stiffness up to 9%, while reducing the static compressive strength up to 24% and stiffness up to 20%. It is concluded that large quantities of embedded optical fibers result in significant degradation of the compressive strength of laminated composite structures, but do not significantly affect the tensile behavior.