Coupled micromechanical modelling for the analysis and prevention of erosion in hydraulic and offshore infrastructures – COMET

The scope of this project concerns the water-flow erosion of geomaterials in relation to the failure of civil engineering infrastructures with large socio-economic relevance such as flood protection dykes and offshore wind-farm foundations. We aim to clarify the underlying mechanisms by which such systems are stressed by a fluid flow until a local dislocation is finally generated within the solid medium, leading to a material loss and eventually to the mechanical instability of the whole structure.
For this, we want to bridge the gap between the micromechanical phenomena at the grain scale and the macromechanical application for engineering problems by developing efficient large-scale coupled simulation models that reproduce directly the interactions between a fluid phase and the bonded assembly of solid particles. To this end, we will couple relevant simulation techniques for the fluid and solid phases (the Lattice Boltzmann Method and the Discrete Element Method, respectively).
We envisage a progressive development of representative models at different scales, at first on a meso-scale to reproduce local phenomena in small setups of our laboratory tests for sake of validation of the numerical calculations, and then increasing in size and complexity up to the real scale of the engineering problems. The models shall feature a solid contact scheme for intergranular cohesion and transient material damage, which are key elements that may govern the macromechanical failure modes of geotechnical systems. A key task at the development stage will be the adaption of our algorithms for parallel computation by means of graphical processors and clusters.
A first field of application shall be the assessment of erosion in hydraulic constructions such as a river levee. In this respect, we will develop detailed micromechanical models of typical erodibility assessment scenarios and analyse the dependencies of the resulting parameters on the granular properties and geotechnical characterizations of the soil. The validated scenarios shall then be upscaled to simulate locally their real-scale counterparts within a practical levee erosion problem for which we already have experimental data from previous in situ tests in 2016 and 2017.
In parallel, the second field of application concerns the foundation structures for offshore wind-turbines. A detailed assessment of different scouring scenarios shall provide a basis for optimized foundation designs and help reduce the costs of windfarm developments. Besides, promising innovative foundations in the offshore field, such as the Suction Buckets, are still not well established due to largely unresolved questions concerning their dual interaction to both the marine soil and the pore water. The stability of the suction mechanism as well as the possibility of a localized hydraulic failure (piping) of the buckets during their installation are key questions that will be addressed here. The development of the intended models dealing with such phenomena from a micromechanical perspective shall provide answers which have been missing in the offshore practice so far.