Strain-Rate Dependence of Strength of the Gulf of Mexico Soft Sediments

Many marine civil engineering applications require knowledge and understanding of the behavior and strength properties of soft cohesive marine sediments under high strain-rate conditions, typically encountered during impact penetration events of sediment probes and other objects as a result of free fall through the water column. To investigate these effects, a series of variable rotational rate vane shear tests was performed on a sample of Gulf of Mexico marine mud, using a precision rheometer and spanning the rotational rate range of 0.25-1000 r/min. A wide range of water contents from 55% to 95% (liquidity index: 1.5-3.3) was examined as a primary influence on the response of a particular saturated silty clay material. Nonlinearities in the behavior of this soil were analyzed, and applicability and precision of various models were examined. A modified rate equation is suggested yielding good correlation with experimental data at all water contents and all rotational rates explored. A testing schedule for a complete material constant derivation procedure is outlined.