Laboratory measurements of compressional and shear wave properties in reconstituted mud and comparison to marine sediment acoustic propagation models

Abstract

Laboratory measurements were performed to characterize propagation of compressional and shear waves in mud, whose composition differs significantly from granular marine sediments like sand or silt. Muddy sediments are colloidal suspensions of thin, irregularly shaped platelets that carry surface charges linked to their cation exchange capacities. These suspensions result in flocculent structures, which cause mud to have high porosity and exhibit gel-like behavior. Samples of reconstituted mud were prepared by mixing kaolinite powder with distilled water and then placing them under vacuum to remove air bubbles entrained by the mixing process. Pairs of hydrophones and benders elements were immersed in the samples to measure compressional (50 kHz to 500 kHz) and shear (0.1 kHz to 1.5 kHz) wave speed and attenuation, respectively. A resonator tube technique was used to infer compressional wave speed at lower frequencies (1 kHz to 10 kHz). Wet-dry mass measurements characterized the density and porosity of dif...