An In Situ Vane System For Measuring Deep Sea Sediment Shear Strength

An In Situ Vane (ISV) system has been developed to determine the detailed strength profile of deep sea clay sediments. The device is designed for deployment of up to one year in water depths of 6000 meters (600 bars), is capable of measuring sediment shear strengths from 0.5 kPa to 70 kPa, and takes multiple measurements to depths of 1.5 meters in the sediment column. A shorter (60 cm penetration) prototype version has been successfully tested at a pressure of 550 bars for 30 days. The system consists of three separate units: a vane shear probe which is housed in a pressure-compensated, oil-filled housing to reduce the seal friction in the sensitive extendable probe, a microprocessor-based control and data acquisition system which is housed in a Benthos 17.8 cm diameter Deep Sea Housing, and a rechargeable battery power supply contained in a Benthos 43.2 cm Glass Sphere. Electrical connections are made using pressure-balanced, oil-filled cables and metal-shell connectors to reduce seawater intrusion problems.