Experimental Study on the Shear Characteristics of Deep-Sea Sediments Based on a Mining Machine Walking Test Platform

The exploitation and utilization of deep-sea mineral resources is an important measure to ensure the safety of resources. The shear characteristics of deep-sea sediments are fundamental parameters for the design of a machine for mining polymetallic nodules. To investigate the shear characteristics of deep-sea sediments, a comprehensive experimental platform is designed independently to drive mining machines. This platform can perform a series of simulated shear tests between the track board and deep-sea sediments. The shear tests investigate the effects of earth pressure, shear rate, and overlying water on shear characteristics between tracks and sediments. The results show that the shear deformation process of deep-sea sediments has four obvious stages, namely linear elastic stage, strain hardening stage, strain softening stage, and residual stress stage. The shear strength of deep-sea sediments increases with the earth pressure. The shear strength of deep-sea sediments decreases significantly under the influence of the overlying water. When the overlying water is applied for 1 h, the peak strength decreases by about 26% and the residual strength by about 70% compared to the strengths without water. When the overlying water is applied for 1 day, the peak strength decreases by about 36% and the residual strength by about 90%. This study provides a theoretical basis for analyzing the running behavior and structural design of crawler mining machines.