Field trial of an acoustic emission early warning system for slope instability

Slope failures world-wide cause many thousands of deaths each year and damage built environment infrastructure costing billions of pounds to repair, resulting in thousands of people being made homeless and the breakdown of basic services such as water supply and transport. There is a clear need for low cost instrumentation that can provide an early warning of slope instability to enable evacuation of vulnerable people and timely repair and maintenance of critical infrastructure. Current instrumentation systems are either too expensive for wide scale use or have technical limitations. An approach, Assessment of Landslides using Acoustic Real-time Monitoring Systems (ALARMS), has been developed and demonstrated through research. An approach developed using measurement of acoustic emission generated during the onset of slope failure to provide quantitative information on slope displacement is described. Sensor operation, deployment strategy, laboratory validation and field performance is considered. The paper presents the results of a field trial of acoustic sensors on an active landslide at Hollin Hill, North Yorkshire, and introduces additional ongoing tri-als in the UK and Italy. Real-time monitoring of acoustic emission generated by the deforming slope has been compared to traditional inclinometer slope displacement measurements. Analysis of the results of the field trial has established that there is a direct relationship between AE and displacement rate trends triggered by rainfall events. Slope deformation events have a characteristic ‘S’ shaped cumulative AE vs. time relationship indicating initial acceleration followed by deceleration of the slide body.