Fiber Optics Sensors Provide Early Warning for Landslides

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Fiber optic sensors could warn people of imminent landslides, potentially saving lives and reducing destruction.
A team at the Second University of Naples is developing sensor technology that could detect and monitor both large landslides and slow slope movements. The researchers hope to mitigate the effects of these major natural disasters, similar to the way hurricane tracking can prompt coastal evacuations.
Optical fiber sensors embedded in shallow trenches within slopes would detect small shifts in the soil, the researchers said. Landslides are always preceded by various types of pre-failure strains, they said.
While the magnitude of 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. Electrical sensors have long been used for monitoring landslides, but that type of sensor can be easily damaged, the researchers said. Optical fiber is more robust, economical and sensitive.
“Distributed optical fiber sensors can act as a ‘nervous system’ of slopes by measuring the tensile strain of the soil they’re embedded within,” said professor Dr. Luigi Zeni.
The researchers are also combining several types of optical fiber sensors into a plastic tube that twists and moves under the forces of the pre-failure strains. This will allow them to monitor the movement and bending of the optical fiber remotely to determine if a landslide is imminent.
The use of 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,” Zeni said.
He added that such sensors can be used to cover several square kilometers and monitored continuously to pinpoint critical zones.
The team will present their research at Frontiers in Optics in Tucson, Ariz., next month.

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