Wave Propagation in Water-saturated Sand and Grain Contact Physics

Abstract

Measurements in sandy ocean sediments 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 observations may be explained in terms of the Biot‐Stoll model with frequency‐dependent complex frame bulk and shear moduli that are governed by the grain‐grain contact physics, and random motion at the grain level. In the case of water‐saturated sands, the contact stiffness is dominated by squirt flow and viscous drag of a thin fluid film that permeates the contact area. Using this approach, the observed sound and shear wave speeds and attenuations may be modeled over a broad band of frequencies.