Numerical Simulations on Liquefaction of Iron Ore Fines under Roll Motion of Bulk Carriers Using Fluid Coupling Scheme in DEM

Numerical simulations are conducted to investigate the dynamics and mechanical characteristics of saturated iron ore fines in bulk carriers by the roll motion using the microscopic fluid coupling scheme devised in the discrete element method. The scheme solves pore water pressure in particle assemblies by the change of void spaces and flows between them. Updated pore water pressure is applied to related particles around void spaces. Two types of bulk carriers are modeled, as well as changing roll conditions for simulations. The results represent liquefaction-that is, the pore water pressure increases while effective stress decreases in particle assemblies as the roll motion proceeds. The relative motion between particles increases especially in the upper area, with particles moving laterally along the surface, such that the surface tilts relative to the lateral direction. In the case of a bulk carrier with a roll angle of 20 degrees, the ratio of excess pore water pressure to initial effective overburden pressure reaches about 70% at a depth of 5 m, and the magnitude of particle velocities is about 5 m/s on the surface; also, the surface tilts about 6 to 8 degrees during the motion. It was verified that the scheme enables one to examine the dynamics and mechanical characteristics of saturated iron ore fines in bulk carriers and could be a more useful tool to guide their safe carriage if further studies for the unsaturated condition are advanced.