On the practical use of the Material Point Method for offshore geotechnical applications

Abstract

The Material Point Method (MPM) has been developed as a special finite element-based method for large deformation analysis, material flow and contact problems. When it comes to applications in soil, MPM can provide solutions where conventional FEM faces its limitations. Examples of geotechnical applications include landslides, silo filling and emptying, soil pushing and shoveling, as well as structure-soil penetration and installation problems (piles, anchors). In offshore geotechnics one can find several applications of the latter type where an MPM analysis can provide significant added value, such as for monopile penetration, (suction) anchor installation, spud can punch-through and trenching for pipelines and cables. In order to use MPM on a daily basis in practical applications, several numerical difficulties had to be overcome, such as inaccuracies, (numerical) instability, irregularities in strain and stress, contact formulation, boundary determination (applying boundary conditions), and last but not least, dealing with the required computing power. The latter is relevant, since MPM calculations are far more demanding than FEM calculations with a similar calculation grid. In this paper we highlight important numerical solutions that we have implemented for a practical use of MPM in geotechnical applications. Examples are the use of high-order elements and the Dual Domain Material Point method (DDMP) to smoothen strains and stresses, the use of an implicit integration scheme to stabilize calculations, the use of an augmented Lagrangian formulation to enhance the contact algorithm, and the use of dynamics and inertia to deal with local soil failure. Furthermore, the paper demonstrates a number of practical cases where MPM can provide added value in offshore geotechnical applications.