In-Situ Soil Testing in the Central Indian Ocean Basin at 5462-m Water Depth

The optimum design of an integrated mining system for polymetallic nodule mining is mainly dictated by the soil properties of soft seabed at 5000–6000 m depth. The entire weight distribution and traction of the mining machine depends mainly on the bearing strength and shear strength parameters of the soil. The shear strength of the soil also provides useful information for the maneuverability of the mining machine. Also, it is imperative that the mining area be delineated to eliminate vulnerable areas of low strength where the equipment may sink suddenly beyond recovery leading to anchoring of the machine. A remotely operable in-situ soil tester has been developed for 6000m operations with a cone tester and a shear vane tester and tested for operations. This paper describes the methodology used for soil property measurements and equipment's performance at 5462 m water depth in the Central Indian Ocean Basin (CIOB)