A fluid-solid coupled micromechanical simulation of a seabed foundation will be presented using the waLBerla multiphysics framework [1] for the analysis of localized fluidization (so-called piping erosion) [2] during the installation process of a suction bucket for the basement of an offshore wind turbine [3]. The fully-resolved simulation will involve a discrete element method representation of the solid phase (i.e., the structural element and the single grains of the sandy seabed) and a lattice Boltzmann hydrodynamic model of the percolating water. We focus on the local phenomena around a representative cut of the full-scale foundation during the first meters of the suction-driven installation. To enable the latter scenario, we will be concerned at first with the creation of the initial seabed conditions in terms of a representative granular fabric involving layered deposition, granular cementation, and a realistic state of intergranular forces and relative density throughout the embedment depth. The subsequent simulation of the grain-resolved flow will pose a significant computational challenge, for which we use highly optimized and parallel code utilizing the capabilities of state-of-the-art heterogeneous supercomputers containing Graphics Processing Units (GPUs). We employ momentum exchange between the fluid and solid phases. The relevance of potential improvements to the current two-way coupling will be investigated, for instance, with the inclusion of lubrication models. The proposed approach enables novel insights into the triggering conditions for piping failure of suction buckets during the installation process of an offshore wind turbine foundation. [1] M. Bauer at al., walberla: A block-structured high-performance framework for multiphysics simulations. Computers & Mathematics with Applications, 2021. [2] R. Ragnir at al., Observations during suction bucket installation in sand. International Journal of Physical Modelling in Geotechnics, 2020. [3] H. Sturm, Design aspects of suction caissons for offshore wind turbine foundations. Unearth the Future, Connect beyond. Proceedings of the 19th International Conference on Soil Mechanics and Geotechnical Engineering, 2017.