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Quantification of acoustic emission from soils for predicting landslide failure

By M.P. Spriggs

Abstract

A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.Acoustic emission (AE) is a natural phenomenon that occurs when a solid is\ud subjected to stress. These emissions are produced by all materials during pre\ud failure. In soil, AE results from the release of energy as particles undergo small\ud strains. If these emissions can be detected, then it becomes possible to develop an\ud early warning system to predict slope failure. International research has shown\ud that AE can be used to detect ground deformations earlier than traditional\ud techniques, and thus it has a role to play in reducing risk to humans, property and\ud in mitigating such risks.\ud This thesis researches the design of a system to quantify the AE and calculate the\ud distance to the deformation zone, and hence information on the mechanism of\ud movement.\ud The quantification of AE is derived from measuring the AE event rate, the output\ud of which takes the form of a displacement rate. This is accurate to an order of\ud magnitude, in line with current standards for classifying slope movements The\ud system also demonstrates great sensitivity to changes within the displacement rate\ud by an order of magnitude, making the technique suitable to remediation\ud monitoring.\ud Knowledge of the position of the shear surface is critical to the planning of cost\ud effective stabllisation measures. This thesis details the development of a single\ud sensor source location technique used to obtain the depth of a developing or\ud existing shear surface within a slope. The active waveguide is used to reduce\ud attenuation by taking advantage of the relatively low attenuation of metals such as\ud steel. A method of source location based on the analysis of Lamb wave mode\ud arrival times at a smgle sensor is summansed. An automatic approach to source\ud location is demonstrated to locate a regular AE source to within one metre. Overall consideration is also given to field trials and towards the production of\ud monitoring protocols for data analysis, and the implementation of necessary\ud emergency/remediation plans

Topics: Acoustic emission, Source location, Waveguide, Slope instability, Lamb waves, AE event rate
Publisher: © Matthew Spriggs
Year: 2005
OAI identifier: oai:dspace.lboro.ac.uk:2134/10903

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