Researchers in Italy are embedding distributed optical-fiber sensors in shallow trenches within slopes to detect and monitor both large landslides and slow slope movements. The team will present their research at The Optical Society's (OSA's) 98th Annual Meeting, Frontiers in Optics (Oct. 19-23; Tucson, AZ). The motivation is to create a landslide early-warning technology.
Predicting landslides by detecting land strains
Landslides are failures of a rock or soil mass, and are always preceded by various types of pre-failure strains known as elastic, plastic, and viscous volumetric and shear strains. While the magnitude of these pre-failure strains depends on the rock or soil involved, ranging from fractured rock debris and pyroclastic flows to fine-grained soils, they are measurable.
Conventionally, electrical sensors are used for monitoring landslides, but such sensors are easily damaged. Optical fiber sensors are more robust, economical, and sensitive.
Luigi Zeni, who is in the Department of Industrial & Information Engineering at the Second University of Naples, and his colleagues combined several types of optical fiber sensors into a plastic tube that twists and moves under the forces of pre-failure strains. The movement and bending of the optical fiber can then be monitored remotely to determine if a landslide is imminent.
The use of novel fiber optic sensors "allows us to overcome some limitations of traditional inclinometers, because fiber-based ones have no moving parts and can withstand larger soil deformations," says Zeni. "These sensors can be used to cover very large areas -- several square kilometers -- and interrogated in a time-continuous way to pinpoint any critical zones."
Presentation FTu2B.4, "Distributed Fiber Optic Sensing Techniques for Soil Slope Monitoring," takes place Tuesday, Oct. 21 at 11:30 a.m. MDT at the Arizona Ballroom, Salon 9 at the JW Marriott Tucson Starr Pass Resort in Tucson.
Frontiers in Optics (FiO) 2014 is The OSA's 98th Annual Meeting and is being held together with Laser Science, the 30th annual meeting of the American Physical Society (APS) Division of Laser Science (DLS). For more info, see www.FrontiersinOptics.org.