A study on simplification of the Biot–Stoll model in water-saturated porous medium

Abstract

A practical approximate method based on the Biot–Stoll model to represent acoustic waves in the ocean in the presence of porous sediment is presented. The ocean sediment can be described individually by four models; visco-fluid, visco-elastic, equivalent fluid, and water-saturated porous medium. The first two models are approximate forms of the Biot–Stoll model. The equivalent fluid model of Zhang and Tindle [J. Acoust. Soc. Am. 98, 3391–3396 (1995)] derived for the fluid/solid interface is extended to the fluid/porous-medium interface for analytical derivation of the reflection coefficient. Then, the reflection characteristics as functions of frame stiffness (Kb/Kr) and frequency region (f/fc) are discussed for all four models. In weak stiffness and high-frequency region, the equivalent fluid and visco-fluid bottom models describe ocean bottom better than the visco-elastic bottom model. Two-phase property is dominant in strong (high) stiffness or high-frequency region. This demonstrates that the visco-fluid and equivalent fluid models are useful approximate models in weak stiffness porous material such as the marine sediment.