Application of Biot Theory to the Study of Acoustic Reflection from Sediments

摘要

Wave Propagation in fluid-saturated poroelastic media may be described using thetheory developed by M. A. Biot between 1941 and of 1962. The treatment is phenomenological and encompasses a wide range physical mechanisms that affect the acoustic properties of porous media. Novel aspects of the theory are the prediction of a second slow compressional wave, frequency dispersion of compressional and shear wave velocities, and an attenuation that is not linearly dependent on frequency. These predictions have been experimentally confirmed only relatively recently. Biot theory may also be used for prediction of reflection and transmission of acoustic waves at a fluid-porous media boundary. In this work, wave propagation in fluid-saturated, porous media are reviewed. Examples of velocity and attenuation dispersion as functions of frequency are shown. The ocean bottom reflection coefficient for a medium sand bottom computed using the Biot theory as functions of grazing angle and frequency is compared against the more common fluid-fluid and fluid-solid interface models. Finally, shallow water propagation loss measurements are compared with model results using Biot theory to predict frequency-dependent bottom loss. Good agreement with measured data is found at all frequencies considered, from 100 to 8000 Hz. Acoustic Reflection, Longitudinal Wave, Biot Theory, Medium Sand Sediment. Bottom Loss,