Autonomous Seafloor Strength Profiler: Comparison of In-Situ and Core Results

The autonomous seafloor strength profiler (ASSP) has been developed to determine the strength profile of the upper 1.5 m of marine sediments. The system can operate in water depths to 6000 m and is designed to remain in a dormancy state of up to one year. The instrument consists of four integrated packages: controller and data acquisition system, mechanical system, volume/pressure compensator, and power supply. This paper describes the ASSP system and presents results of in situ vane tests in a deep sea (5845 m) illitic clay and shallow water (60 m) clayey silty fine sand. The in-situ shear strengths of the deep sea clay are 26% higher than those of core samples. The shear strength profile for the shallow water sediment is quite different from that of a nearby core.