Optimisation of acoustic emission sensor- waveguide assembly for soil slope instability measurement

Abstract

Acoustic emission technology (AET) based soil slope monitoring is one of the most innovative and economically viable method that exhibits immense potential in the framework of a landslide early warning system (LEWS). Essential components of AET are AE sensor for soil originated AE signal detection and capturing, active wave-guide to tackle with high AE signal attenuation of soil media, and data acquisition and analysis system (DAAS) for AE parameter extraction, signal conditioning and data storage. AE signal parameters can be exploited to assess and evaluate the soil slope instability. The magnitude, rate, and acceleration of soil slope deformation are direct measures of slope instability. Research articles oriented around AET based soil slope monitoring are prominently focussed on the correlation between slope deformations and its AE behaviour, leaving the AE sensor and waveguide assembly effects unattended. The sensitivity of AET based LEWS is reliant on the performance of the AE sensor and active waveguide, since these are the components responsible solely for collecting relevant AE data from the slope. We have experimented with variety of active waveguide materials and designs, and optimised it for better performance with respect to soil slope deformation parameters. In the studies, two kinds of AE sensors are utilised: one resonant AE sensor and one broadband AE sensor. Steel and aluminium are used as waveguide material. Different grades of high-density polyethylene pipes are used as flexible membrane of the active waveguide. The experimental design and results are described in this article. For simulating real-time landslide slope conditions, a tilt trolley set-up is used for testing the optimised AE sensor-waveguide set-up. Futuristic aspects of the set-up in context of design and development of a LEWS are also discussed.