Files in this item



application/pdf3153250.pdf (16MB)Restricted to U of Illinois
(no description provided)PDF


Title:Coupled Acoustic and Electromagnetic Disturbances in a Granular Material Saturated by a Fluid Electrolyte
Author(s):Block, Gareth Ian
Doctoral Committee Chair(s):Harris, John G.
Department / Program:Theoretical and Applied Mechanics
Discipline:Theoretical and Applied Mechanics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Physical Oceanography
Abstract:We devised two reciprocal experiments to study these phenomena. "EK transmission" occurs when an applied voltage creates an electro-acoustic wave; in practice, this leads to thermoelastic motion, as well as electrokinetics, so that we have had to account for both effects. Conversely, "EK reception" occurs when a pressure wave generates a measurable voltage in electrolyte-saturated sediments. The EK reception apparatus made use of a submerged, acoustic transducer to insonify a water-sediment interface with short, 50 kHz sine-wave bursts and chirped pulses from 10--800 kHz. The resulting wave motion was monitored using Ag/AgCl electrodes fixed in a vertical array above and below the sediment interface. We measured the conductivity dependence of two kinds of EK behavior: (1) voltages generated within the samples that were localized around the transmitted "fast" waves, and (2) electromagnetic (EM) waves produced at the water-sediment interface. Fast-wave voltages were often greater than 500 muV, while the EM-wave potentials were usually 100 muV in magnitude. A model of plane-wave reflection from a water-EK-Biot interface leads to theoretical predictions that compare very well to experimental data for sand and glass microspheres. Both EM- and fast-wave voltages are caused by relative fluid motion in the sediment, a feature that is characteristic of poroelastic media---but not predicted by either fluid or solid models.
Issue Date:2004
Description:160 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2004.
Other Identifier(s):(MiAaPQ)AAI3153250
Date Available in IDEALS:2015-09-28
Date Deposited:2004

This item appears in the following Collection(s)

Item Statistics