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The predicted depth of mines buried in marine muds is generally based on estimates of sediment shear strength (often unreliable). Conversely, sediment states of marine muds are water-dependent, defined empirically by the Atterberg Limits (liquid limit and plastic limit), and allow the sediment to be described as having fluid-like, plastic-like, or semi-solid consistency. When the natural water content and the liquid limit of normally and unconsolidated marine muds are approximately equal at depth below the seafloor, the mud at greater depth is considered to no longer behave as fluid-like, but plastic-like. This relationship provides a predictable conservative minimum mine burial penetration depth. Mine burial depths at two sites were shown to closely agree with predicted burial depths based on the natural water contents and the liquid limits (Bennett et al., SEAPROBE, Inc., Technical Report Number SI-0004-01, p., 89, 2004, funded by ONR). Prediction of selected sediment physical properties using acoustic impedance as a function of depth below seafloor may provide a method to estimate and evaluate sediment states. Comparison of subbottom natural water contents with a database showing known liquid limits for different types of marine muds should make possible prediction of conservative, minimum, mine burial depths.

The study and quantification of selected sediment properties important to the modeling of high frequency sound interaction in ocean sediments is the long-term project goal. Understanding of the coupling of sound into sediments, of propagation and attenuation within sediments, and of scattering from the sediment-water interface are the ONR program goals (Thorsos et al., 2001). The environmental measurements research thrust is twofold. Part I is the in situ three-dimensional measurement and quantification of sandy sediment permeability. Part II is a quantitative study of the sediment microfabric, pore fluid pathways, porometry, and bio-organic components. A goal of the microfabric investigations is the development of microfabric models and related numerical analysis that describe important sediment properties such as fluid flow characteristics, tortuosity, isotropy and anisotropy, and stress-strain behavior.