Acoustic emission characterization of soil shear deformation using active waveguide systems

Acoustic emission (AE) sensing offers a non-destructive approach for monitoring deformations in granular geomaterials with potential for landslide early warning system (LEWS). In this study, the AE characteristics generated during controlled large-scale soil shear deformation were investigated using active waveguide system (AWS) embedded in a custom-developed shear apparatus. Constant shear displacement rates ranging from 0.005 to 30.0 mm/min, along with accelerating and decelerating deformation histories, were imposed to examine the evolution of AE activity, cumulative counts, signal duration, energy, and frequency-domain characteristics across defined deformation velocity scales. Cumulative AE counts exhibited a quadratic relationship with elapsed time for all constant-rate tests. The square root of the quadratic coefficient (√β) was proportional to the imposed shear displacement rate, demonstrating the potential of cumulative AE counts for laboratory calibration of deformation velocity. Under the controlled laboratory conditions, frequency-domain analysis revealed concentrated centroid-frequency of 70-90 kHz and concentrated peak-frequency of 30-80 kHz, representing the combined response of granular source mechanisms and the soil-AWS-sensor system. Variable-rate experiments also showed the sensitivity of AE parameters to transitions between successive deformation regimes. The proposed relationships provide a laboratory-calibrated framework for non-destructive characterisation of soil shear deformation and establish a basis for future site-specific calibration of AE-based LEWS.