Listening for landslides

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Landslides happen around the world and often have disastrous consequences, costing thousands of lives and damaging critical infrastructure. Engineers from Loughborough University have developed an early warning system that listens for the acoustic emissions created by underground soil movements, and alerts those above ground that a landslide is imminent.

The system has two versions: Slope ALARMS, used to monitor critical infrastructure, and Community Slope SAFE, a low-cost version of the early warning system that is operated by local people in communities at risk of landslides. The research has been commercialised by Canadian firm RST Instruments, which has produced the Geo Acoustic Aware Slope Monitoring System.

Dr Alister Smith worked on the project, led by Professor Neil Dixon, through two fellowships from the Engineering and Physical Sciences Research Council (EPSRC). Smith said: "Traditional landslide early warning systems were prohibitively expensive or had technical limitations.

"Our system ‘hears’ a landslide forming, and is useful for at-risk communities, as well as infrastructure owners and operators around the world."

The first version was Slope ALARMS, developed with the British Geological Survey. Community Slope SAFE followed, in collaboration with Datalink Electronics. It was aimed at low- and middle-income countries, so had to be affordable and easy to use and maintain.

A steel tube called a waveguide is driven into the slope in landslide risk zones. Inside its protective cover is a solar battery-powered sensor. If the slope moves, the soil in and around the tube generates high-frequency noises known as acoustic emissions. These are transmitted from within the slope, up through the tube and to the sensor, where the mechanical energy is converted into an electrical signal. If a threshold is exceeded, a warning is transmitted.

Omitting background noise was critical, Smith explained, "We developed the interpretation system to exclude low-frequency noise from sources like transport and agriculture, even heavy rain, to avoid false alarms.

"The success of an early warning system depends on the context and the knowledge at hand. This isn't a magic wand. Areas at risk will still need a geotechnical engineer to understand the nature of the potential landslide and help predict its behaviour."

Community Slope SAFE has been trialled in several locations. A system has been trialled in a hilltop area of Kuala Lumpur since 2017. Local and national politicians attended briefings to find out how the system works and its potential outcomes in an area with a history of slope failures.

In 2018, it was installed in Chin state in Myanmar, where landslides had caused loss of life and damage to infrastructure. Twenty young volunteers were recruited through a local radio appeal, and were trained to install, operate and maintain the system.

Smith and his colleagues at Loughborough University are now applying the acoustic emissions approach to ground behaviour scenarios.

"We initially focused on landslides, but now we’re looking at the impact of ground movements on all sorts of critical infrastructure, from buried pipes to dams.

"Using acoustic emissions to monitor the health of infrastructure is an entirely novel approach. This could transform how we monitor geotechnical assets."