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MPM modelling and simulation of soil-fluid interaction for dredging applications

Final Report Summary - MPM-DREDGE (MPM modelling and simulation of soil-fluid interaction for dredging applications)

Economic activities, population growth, falling land levels and climate change are generating increasing pressure on available resources of (renewable) energy and habitable space in deltas, river basins and coastal areas throughout the world. Advanced technologies and developments in engineering fields (e.g. geotechnical and hydraulic engineering) enable to shift boundaries for exploration and exploitation of oil, gas and wind energy further off coast, and to develop ports and reclaim new land. The latter requires bigger and better defensive structures like breakwaters, revetments and scour protections. In order to be able to protect economically vital and at the same time vulnerable areas against flooding and erosion, today and tomorrow, the dredging industry is forced to persist in pushing back frontiers.

From an engineering point of view, realising structures in this type of hostile environments is much more challenging than building on land. During their construction and use, these structures are not only affected by wind and gravity. They are also constantly exposed to waves, currents and changing seabed characteristics caused by important processes like erosion and deposition. Moreover, the conditions are very site-specific, meaning that standard solutions are often not applicable. Dedicated materials and construction techniques are to be used and a dedicated numerical tool is needed to determine an optimal unique solution.

One approach in investigating soil-fluid interaction is the performance of physical experiments. However, considering the extreme costs of these often large scale experiments, the dredging industry cannot perform those on a regular basis. With the advent of computers and computational mechanics it has become feasible to develop numerical tools for the simulation of dredging operations. In particular the pioneering work of the University of Cambridge (UK) and Deltares (commercial international centre for applied research, based in The Netherlands) constitutes a sound basis for the numerical simulation of soil-fluid interaction. Both institutes have recognised the high potential of the so-called Material Point Method (MPM) for solving soil-fluid interaction problems, and have joined their forces in the MPM-DREDGE project (see http://www.mpm-dredge.eu/project-mpmdredge). With the support of the four largest European dredging companies (i.e. Royal Boskalis, Dredging International, Jan de Nul and Van Oord), the MPM-DREDGE project has focused on three applications for the dredging industry: the dropping of geocontainers, the modelling of liquefaction and the modelling of erosion processes including scouring around offshore structures.

During the MPM-DREDGE project a joint 3D computer code based on the Material Point Method (MPM) has been developed, for modeling large deformation problems for soil-fluid interaction, including generation and dissipation of (excess) pore pressures. New methodologies have been developed and implemented in the joint software Anura3D (http://www.anura3d.com) that combines earlier pioneering work of Cambridge and Deltares in the field of soil-fluid interaction.

Simultaneously, during the MPM-DREDGE project the practical applicability of this numerical tool (specifically for the simulation of dredging applications) has been intensively validated and demonstrated. After all, without a proper validation and verification, the dredging industry cannot be expected to apply such a new numerical method in the dredging practice. For the validation and demonstration, available scale model tests and benchmark problems have been used, and real field applications have been considered through intensive collaboration between (dredging) industry and academia.

In parallel, the project has strengthened and expanded the collaborative link between the MPM-DREDGE partners, and has established a strong and strategic alliance to increase the R&D input and innovation in the (combined) geotechnical and hydraulic engineering fields. This has led to the foundation of the MPM Research Community (see http://www.anura3d.com) which is a strong cooperation of seven equal partners: Univèrsitat Politecnica de Catalunya (ES), University of California (Berkeley, USA), Technical University Delft (NL), Università degli Studi di Padova (IT), Technische Universität Hamburg-Harburg (DE), University of Cambridge (UK) and Deltares (NL). The approach in the collaborative work of this MPM Research Community is problem driven, i.e. the numerical tools are developed in order to solve challenging problems of practical importance for the supporting partners in the dredging business.