Multiscale investigations on the failure mechanism of submarine sand slopes with coupled CFD-DEM

In terms of the construction of gravity offshore foundation systems, the short- and longterm stability of submarine sand slopes is of crucial importance. The heavy structures cannot be placed directly on the sea ground. The weak topsoil has to be excavated to place the structure on more stable ground, which results in a pit. A steep but stable inclination of its slopes would thereby meet both economic and ecologic interests as the disturbed area is reduced. Different hydrodynamic disturbances as tidal streaming or waves are hereby influencing the stability of the submarine slopes. The changes in pore water pressure due to the hydrodynamic disturbances and the interaction of the soil grains with the surrounding pore water significantly influences the stability of the slope and its failure mechanism. To take into account these effects, the numerical simulations are carried out with a multiscale approach, namely a coupling of the Computational Fluid Dynamics (CFD) and the Discrete Element Method (DEM). In this method, the soil particles are modelled on a microscale level, tracking velocity and position in a lagrangian way. The fluid phase is modelled at a macroscale level using CFD. The numerical modelling aims on investigating the effect of tidal streaming on submarine sand slopes with different packing densities to take into account the influence of dilatancy and contractancy.