Deep Sea Soil Sinkage Simulation and Experimental Studies for Development of Deep Water Mining Machine

Abstract

Abstract Technology is being developed to harvest polymetallic nodules from depths of 4,000‐6,000 m in the Central Indian Ocean Basin. Polymetallic nodules are found on the surface and just below the surface of the abyssal plains of the ocean. A deep-water polymetallic nodule mining machine has to reliably move on the soft soil seabed and collect the nodules. The seabed soil is water saturated, soft, and cohesive with a shear strength typically less than 2 kPa. It is vital to design and develop a mining machine and nodule harvesting systems considering the seabed soil environment, with regard to machine supportability, locomotion resistance, traction capability, and locomotion control. Thus, understanding of soil-machine interaction is important in the development of a deep-water mining machine. This study aims to simulate numerically static sinkage in very soft clay of shear strength less than 2 kPa and compare the results with experimental tests under various loading conditions. Finite Element Method‐based simulation using ABAQUS software using Coupled Eulerian Lagrangian technique has been used to predict the sinkage in various layers of soil having different strengths (from previously tested parameters) in close simulation of the actual seabed conditions. The paper includes a study undertaken with two types of grousers to observe the deformation of the soil. The effects of different bearing pressures on layered soil strength conditions with different grousers have been simulated in deducing the sinkage results.