Inclinometer casings retrofitted with acoustic real-time monitoring systems

The paper details the concept of retrofitting inclinometer casings with active waveguides in order to provide subsurface instrumentation that can monitor the stability of slopes continuously and in real-time. The operation of the active waveguide, the unitary battery operated Slope ALARMS acoustic emission sensor and warning communication system are described. A field trial previously reported by the authors demonstrates that acoustic emission rates generated by active waveguides are proportional to the velocity of slope displacements, and can therefore be used to detect changes in rates of movement (i.e. accelerations and decelerations) in response to destabilising (e.g. rainfall) and stabilising (e.g. remediation) effects. The paper presents the results of a field trial of the acoustic monitoring system retrofitted inside an inclinometer casing in a reactivated landslide at Hollin Hill, North Yorkshire, UK. The study demonstrates that this approach can provide continuous information on slope movements with high temporal resolution. Converting manually and periodically read inclinometer casings into continuously monitored active waveguides using Slope ALARMS sensors is a cost effective solution to provide real-time information that could be used in the protection of people and infrastructure.