Surface wave surveys for imaging ground property changes due to a leaking water pipe

• Published in: Journal of applied geophysics Vol. 174; p. 103923
• Main Authors: Dashwood, Ben, Gunn, David, Curioni, Giulio, Inauen, Cornelia, Swift, Russell, Chapman, David, Royal, Alexander, Hobbs, Peter, Reeves, Helen, Taxil, Julien
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2020
• Subjects: Geophysical monitoring; Multi-channel analysis of surface waves; Shear modulus; Trench excavation; Volumetric water content; Geophysical monitoring; Volumetric water content; Shear modulus; Multi-channel analysis of surface waves; Trench excavation
• ISSN: 0926-9851; 1879-1859
• DOI: 10.1016/j.jappgeo.2019.103923

This study demonstrates the use of Multi-channel Analysis of Surface Waves (MASW) to measure changes in Rayleigh wave velocity relating to both the initial trench construction and subsequent simulated failures (water leaks) of a buried water-pipe. The MASW field trials were undertaken in conjunction with a wider suite of geophysical monitoring techniques at a site in South-west England, within an area of clayey sandy SILT. The Rayleigh wave velocity through a soil approximately equals the shear wave velocity, which in turn is predominantly dependant on the shear modulus of the soil (G) and this can be inferred to give a measure of the relative strength of a soil. It is proposed that the time-lapse measurement of Rayleigh wave velocity may be used to monitor ongoing changes in soil strength and therefore the MASW technique could perform a significant role in monitoring the initiation/progression of any internal processes within a geotechnical asset, before they would otherwise be identified through visual inspection alone. •Non-invasive geophysical method to assess strength-related property changes of the soil hosting a leaking water pipe;•20% reduction in shear wave velocities in trench backfill wrt velocities in the ground prior to excavation of the trench;•Volumetric moisture content of the fill around the leak rose to over 50%, which led to the 20% velocity reductions;•Undetected leaks potentially cause localised (15-20%) decrease in ground strength, posing threat to supported infrastructure;•Non-invasive, geophysical surveys offer proactive inspection opportunities between nodes experiencing pressure drops.