Acoustic emission monitoring of a soil slope: Comparisons with continuous deformation measurements

Abstract

Acoustic emission (AE) has become an established approach to monitor the stability of soil slopes. However, the challenge has been to develop strategies to interpret and quantify deformation behaviour from the measured AE. This paper presents the first comparison of continuous AE (measured using an active waveguide) and continuous subsurface deformation measurements. The active waveguide is installed in a borehole through a slope and comprises a metal waveguide rod or tube with a granular backfill surround. When the host slope deforms, the column of granular backfill also deforms, generating AE that can propagate along the waveguide. This paper presents results from a field trial at a reactivated soil slope in North Yorkshire, UK. The measurements confirm that AE rates generated are directly proportional to the velocity of slope movement (e.g. the AE rate versus velocity relationship determined for a series of slope movement events produced an R 2 value of 0?8) and demonstrate the performance of AE monitoring of active waveguides to provide continuous information on slope displacements and displacement rates with high temporal resolution.

Monitoring buried pipe deformation using acoustic emission: quantification of attenuation

“…A band pass filter attenuated signals outside of the 20 to 30 kHz range to eliminate low-frequency background noise (<20 kHz) and to keep the monitored range consistent with that used in slope monitoring field trials using active waveguides (e.g. Smith et al, 2014a;Smith et al, 2014b;Dixon et al, 2015a;Dixon et al, 2015b;Smith, 2015). Amplification of 70 dB was used to improve the signal to noise ratio.…”

“…Moreover, AE generated by deforming soil is continuous throughout the period of deformation, which could be hours or even days (e.g. Smith et al, 2014a). Because soil generated AE is highly variable and is continuous over long durations, it is not appropriate to attempt to replicate soil-generated AE with a single transient source.…”

“…Generated AE rates are proportional to applied displacement rates, where the coefficient of proportionality Smith et al Monitoring Buried Pipe Deformation Using AE: Quantification of Attenuation 17/08/2016 3 is dependent on the depth to the shear surface and the distance AE propagates along the waveguide to the ground surface where it is measured. Quantifying this magnitude of attenuation for each installation is essential to deriving slope displacement rates from measured AE rates, which can be used to warn users of accelerating slope deformation behaviour to enable evacuation of vulnerable people and timely repair and maintenance of critical infrastructure (Koerner et al, 1981;Nakajima et al, 1991;Smith et al, 2014a;Smith et al, 2014b;Dixon et al, 2015a;Dixon et al, 2015b;Smith, 2015;Smith & Dixon, 2015;Smith et al, 2016).…”

Stability monitoring of a rail slope using acoustic emission

“…Beard, 1961;Cadman and Goodman, 1967;Chichibu et al, 1989;Dixon et al, 2003Dixon et al, , 2014aDixon et al, , 2014bFujiwara et al, 1999;Naemura et al, 1991;Nakajima et al, 1991;Rouse et al, 1991;Smith et al, 2014aSmith et al, , 2014b. Fine-grained soils generate relatively low-energy AE signals, which attenuate significantly over short distances.…”

“…A recent development is the ShapeAccelArray (SAA) (e.g. Abdoun et al, 2013 andSmith et al, 2014a detail case histories where the SAA has been used), which comprises a string of microelectro-mechanical systems (MEMS) sensors installed at regular increments along the length of a borehole (available SAA gauge lengths are 0 . 2, 0 .…”