Characterization of Near Seabed Surface Sediment

摘要

Accurate measurement of the shear strength profile in the upper 1 m of soft sediments is crucial for pipeline and riser design, particularly for deep water developments. In this paper, some existing approaches for the strength characterization of seabed surficial sediments are reviewed and the conclusion reached that performing in-situ strength tests within box core samples is the most reliable means of characterizing the shear strength of soft surficial sediments. A box corer for recovering high quality undisturbed sample of the very soft seabed surficial sediments (upper 0.5 m of the seabed) and a new manually operated penetrometer (DMS) for measuring profiles of undisturbed and remoulded undrained shear strength within the box core sample are described. Field data for DMS tests in box cores recovered from a site in the Gulf of Mexico are presented and compared with the strength data measured by motorized miniature vane tests to evaluate the potential of the DMS in characterizing the shear strength of seabed surficial sediments. These data showed that performing DMS tests in box core sample can provide a reliable and time effective means of obtaining strength profiles (undisturbed and remoulded) of soft seabed surficial sediments.