A porous medium model for mud

Abstract

The extended Biot model for sands and silts is repurposed to include mud, but modifications are needed. The boundary between pore water and skeletal frame needs to be redefined because a significant fraction of the pore fluid is adsorbed onto the solid frame by electrostatic forces, and a proportion of the solid particles may be suspended in the pore fluid. Revil's relationships are used to simplify the input parameters. The frame elasticity equations are corrected to accommodate the sparse skeletal frame, which is supported by electrostatic forces, and behaves differently to a mechanical packing of grains. The corrected, Revil, extended Biot model has just four fitting parameters and is compared with published measurements of wave speeds and attenuations in the literature of clay, silty clay, and clayey silt sediments including recently published measurements from the Seabed Characterization Experiment. The results indicate that the skeletal frame in clay has a high water-content and the pore water contains suspended particles. To fit all the currently available data, it was necessary to modify corrected, Revil, extended Biot by flattening the creep related relaxation loss spectrum. There is a similarity with the Viscous Grain Shearing models in the use of a fractional exponent.

Laboratory seismic measurements for layer-specific description of fluid mud and for linking seismic velocities to rheological properties

“…Meredith (1987) found that the S-wave velocities range from 740 to 1000 m/s using the inversion results from borehole logger data from 390 to 582 m below the seafloor. In the study by Chotiros (2021), the modeling of shear-wave velocities from low to high frequencies predicts a shear-wave velocity between 100 and 200 m/s at 1 MHz for the clay sample from Eckenforde Bay and a shear-wave velocity between 400 and 700 m/s at 1 MHz for the clayey silt sample from Eel River. The measurement technique, sediment type, and cementation contribute to the fact that the S-wave velocities we observe are higher-above 959 m/s.…”

“…Using physics-based models is challenging for predicting seafloor seismic properties (Jackson and Richardson, 2007). Empirical models (Hamilton, 1979) and physics-based models (Stoll, 1977;Buckingham, 1997;Buckingham, 2005;Chotiros, 2021) can be used to predict the propagation velocities of waves.…”