Sound Speed and Attenuation Measurements in Unconsolidated Glass Bead Sediments Saturated With Viscous Pore Fluids.

摘要

During the sediment acoustics experiment (SAX99) independent sound speed and attenuation measurements were made in a well-characterized sandy sediment. These measurements covered a broad frequency range that made it possible to test both Biot theory and Buckingham's more recent grain-to-grain attenuation model. Biot theory was able to model sound speed well but was unable to predict attenuation measured above 50 kHz. A series of measurements was made in the laboratory to test the hypothesis that this modeling deviation was due to scattering within the sediment. The measured attenuation in the glass bead sediments exhibited the same frequency dependence observed in the SAX99 data, indicating that scattering is not the relevant attenuation mechanism. A sediment model is proposed which is a hybrid of the Biot and Buckingham theories. This hybrid model is able to predict both attenuation and sound speed in the SAX99 sediment and in the laboratory sediments. The implications of the success of the hybrid model are discussed.