Acoustic emission monitoring of active waveguides to quantify slope stability

The active waveguide is installed in a borehole that penetrates stable stratum below any shear surface or potential shear surface that may form beneath a slope. It comprises a metal waveguide rod or tube that provides a low resistance path for acoustic emission to travel from the source at the shear surface to the sensor at the ground surface. The annulus surrounding the waveguide is backfilled with granular soil. When the host slope deforms, the column of granular soil also deforms and this induces inter-particle friction and releases relatively high levels of acoustic emission that can propagate along the waveguide. Field trials and laboratory experiments reported by the authors have demonstrated that acoustic emission rates generated by active waveguides are proportional to the velocity of slope movement. This summary describes the operation of the active waveguide and Slope ALARMS acoustic emission sensor for use in slope stability monitoring. An on-going research project aiming to develop an algorithm that can quantify slope displacement rates through monitoring active waveguide generated acoustic emission is introduced.