New acoustic early warning system for landslides developed
By Ben Coxworth
October 22, 2010
People living in landslide-prone areas will be glad to know that a new technology has been developed which monitors soil acoustics to determine when a landslide is imminent. The system consists of a network of sensors, buried across a hillside considered a risk. As soil moves within the hillside, it creates noise – the more the amount of movement, the louder the noise. When that noise reaches a threshold level, the system sends a text message warning to local authorities, that a landslide is about to occur.
The system was developed by Dr. Neil Dixon, a professor of geotechnical engineering at Loughborough University in the UK. “In just the same way as bending a stick creates cracking noises that build up until it snaps, so the movement of soil before a landslide creates increasing rates of noise,” he explained. “This has been known since the 1960s, but what we have been able to do that is new is capture and process this information so as to quantify the link between noise and soil displacement rates as it happens, in real time and hence provide an early warning.”
Each sensor consists of a long steel tube, known as a wave guide, topped with a piezo-electric transducer. Vertical holes are bored along the hillside, which can extend tens of meters beneath the surface, depending on the depth of the unstable soil. Wave guides the same length as each of those holes are then inserted, and gravel is packed in around the outside of them, from top to bottom.
As the soil in the hillside moves, the gravel moves also, and the acoustic stress waves created by its movements travel up the wave guides, where they are registered by the transducers. The transducers convert the energy of the waves into electrical signals, which are sent to a central computer. When that computer determines that there’s too much soil movement, it sends out a warning.
Dixon and his colleagues are now working on simpler sensors that don’t require a central computer, but instead are each capable of emitting their own visual and/or audible alarms. They are intended for use in developing nations, that can’t afford more complex systems. The Loughborough team is working with the Engineering and Physical Sciences Research Council to commercialize the technology, and hopes to have a finished product available within two years.