A broadband model of sandy ocean sediments: Biot-Stoll with contact squirt flow and shear drag

Unlike the application of the Biot model for fused glass beads, which was conclusively demonstrated by Berryman [Appl. Phys. Lett. 37(4), 3 82-384 (1980)] using the experimental measurements by Plona [Appl. Phys. Lett. 36, 259-261 (1980)], the model for unconsolidated water-saturated sand has been more elusive. The difficulty is in the grain to grain contact physics. Unlike the fused glass beads, the connection between the unconsolidated sand grains is not easily modeled. Measurements over a broad range of frequencies show that the sound speed dispersion is significantly greater than that predicted by the Biot-Stoll model with constant coefficients, and the observed sound attenuation does not seem to follow a consistent power law. The sound speed dispersion may be explainable in terms of the Biot plus squirt flow (BISQ) model of Dvorkin and Nur [Geophysics 58(4), 524-533 (1993)]. By using a similar approach that includes grain contact squirt flow and viscous drag (BICSQS), the observed diverse behavior of the attenuation was successfully modeled. (C) 2004 Acoustical Society of America.