HR: 0800h
AN: MR11A-0905    [Abstracts]
TI: Measuring Porosity and Tortuosity of Rocks by Means of Air Ultrasound
AU: Hoffren, H
EM: hannu.hoffren@helsinki.fi
AF: Electronics Research Unit, Department of Physical Sciences, University of Helsinki, P. O. Box 64 (Gustaf H„llstr”min katu 2), Helsinki, 00014 Finland
AU: Karppinen, T
EM: timo.karppinen@helsinki.fi
AF: Electronics Research Unit, Department of Physical Sciences, University of Helsinki, P. O. Box 64 (Gustaf H„llstr”min katu 2), Helsinki, 00014 Finland
AU: * Kohout, T
EM: thomas.kohout@helsinki.fi
AF: Division of Geophysics , Department of Physical Sciences, University of Helsinki, P. O. Box 64 (Gustaf H„llstr”min katu 2), Helsinki, 00014 Finland
AU: Haeggstr”m, E
EM: haeggstr@mappi.helsinki.fi
AF: Electronics Research Unit, Department of Physical Sciences, University of Helsinki, P. O. Box 64 (Gustaf H„llstr”min katu 2), Helsinki, 00014 Finland
AU: Pesonen, L
EM: lauri.pesonen@helsinki.fi
AF: Division of Geophysics , Department of Physical Sciences, University of Helsinki, P. O. Box 64 (Gustaf H„llstr”min katu 2), Helsinki, 00014 Finland
AB: An ultrasonic burst reflection method for estimating porosity and tortuosity of rocks is being developed. This method is based on measuring ultrasound reflection from the first interface of a solid material as a function of incidence angle [1]. The reflected 600 kHz waveform is compared to the wave reflected from a polished steel mirror to obtain estimates for the porosity and the tortuosity of the sample. As a milestone on our way to prove the suitability of this method to determine the structural properties of rock materials we report on our first results measured on micro sphere - silicon samples of 5-50% porosity. The proposed method is intended for applications in rock physics where porosity is an important parameter that provides information about the origin and evolution of the rock sample. The method should also find application in meteorite characterization since meteorite porosity carries information about the evolution and structure of meteorite parent bodies. This method is fast, inexpensive and non-destructive in comparison to other current laboratory methods that determine the porosity. The samples are relatively easy to prepare for the measurement, as well. After some improvements this ultrasonic measurement system could be used as an automated portable field measurement device without moving parts. The only requirement is the presence of a flat and polished surface on the rock sample. The necessary surface preparation can also be performed with portable device [2]. References: [1] Z.E.A. Fellah, et.al., "Measuring the porosity and the tortuosity of porous materials via reflected waves at oblique incidence" J. Acoust. Soc. Am 113 (5) p.2424-2433 (2003) [2] http://mars.jpl.nasa.gov/mer/mission/spacecraft\_instru\_rat.html
DE: 5100 PHYSICAL PROPERTIES OF ROCKS
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting