Shear wave attenuation measurements were made
using ceramic bimorph transducers to excite transverse
vibrations in a cylindrical column of unconsolidated
sediment. Three different water-saturated
sediments were used in an attempt to determine the
effects of grain shape and sorting on the frequency
dependence of attenuation. The mean grain size of the
sediments was held constant while the grain shape and
size distributions were varied. The sediment assemblages
used in the attenuation measurements included
a moderately-sorted angular quartz sand, a well-sorted
angular quartz sand, and well-sorted spherical
glass beads. The moderately-sorted sand showed the
greatest attenuation over the measurement frequency
range of 1 to 20 kHz. The well-sorted sand and the
glass beads showed generally lower attenuation with
the beads being the least lossy propagation medium.
All three sediments showed evidence of viscous attenuation
due to fluid-to-grain relative motion. This
mechanism leads to a non-linear relationship between
attenuation and frequency.
Sediment physical properties were measured for
use as inputs to a theoretical attenuation model based
on the Biot theory of propagation of waves in porous
media. The model allowed attenuation versus frequency
predictions to be made for each of the three sediment
assemblages. The resultant comparisons between the
measured and predicted attenuations demonstrated the
importance of using measured model inputs obtained
under controlled laboratory conditions when theoretical
model capabilities are being evaluated. The model
comparison shed significant light on the ability of
this particular model to predict shear wave attenuation
in non-ideal sediments. / Graduation date: 1984
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/26762 |
| Date | 23 June 1983 |
| Creators | Brunson, Burlie A. |
| Contributors | Johnson, Richard K. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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