In this paper, the particular mechanical interaction relationships between a seafloor tracked miner and the sediment are obtained through laboratory-simulated experiments. Underwater sediments exhibit entirely different shear properties compared to land surface soils. An innovative user-written subroutine for characterizing the mechanical models of various soil types is compiled and linked to the RecurDyn simulation environment and then validated against an available commercial program and with laboratory tests. A new three-dimensional multi-body dynamic simulation model of the miner is developed in RecurDyn by integrating the developed mechanical model of the seafloor sediment. Simulations are conducted to measure the miner's geometric trafficability and locomotion performance. Additionally, a mathematical model to evaluate the miner's tractive trafficability in relation to its slip ratio and its primary design parameters is established, and the results demonstrate that there is an optimum slip ratio that produces a maximum traction force for the miner. This research provides a valuable and effective simulation modelling method for trafficability, locomotion predictions, design optimization and motion control of tracked-operated vehicles under various terrain conditions.

In this research, the mechanical characteristic parameters of the seabed massive sulfide (SMS) are obtained quantitatively using laboratory uniaxial compression strength (UCS) test and triaxial compression strength (TCS) test. A three-dimensional discrete element (DEM) model of the SMS is developed in the EDEM simulation environment and are then validated by numerically simulating the laboratory UCS and indirect tensile strength (Brazilian disc) tests. A new counter-rotating pick-type drum cutter for excavating the SMS is proposed, and a corresponding DEM model for the excavation process is established. Numerical simulations for the new counter-rotating cutter and a traditional single-rotating cutter are conducted, and the cutter forces in three orthogonal directions and the torques are obtained and compared. By integrating the new counter-rotating cutter, a three-dimensional multi-rigid-body dynamic model of a SMS mining machine is developed in the RecurDyn simulation environment, and simulations are conducted to evaluate its trafficability and mobility performance under the effect of the excavating cutter on the seabed complex terrain. This research can provide valuable and effective modelling methods for seabed mineral excavation process simulation, mining tool optimization and design and mining machine performance evaluation.