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Discrete Element Modelling (DEM) is a method which is designed to simulate the behaviour of a material
by modelling the interactions between discrete elements i.e. particles. The mechanical interactions between
particles and also between particles and the walls in are modelled by springs, dash-pots and friction sliders.
The properties of the material and interactions (Poisson's ratio, shear modulus and density, coefficients of
restitution, rolling and static friction) relate to the particle properties and not to the bulk properties. If DEM
(using software like EDEMTM & PFCTM) is reliable by validation with analytical models, it will have many
applications in dredging, specifically for investigating underwater cutting processes in sand, clay and rock.
Since people have no real experience with this method in dredging, the first step is to model a number of
well-known examples like passive earth pressure and the cutting of dry sand and compare the simulation
results with the analytical solutions. During this first step the relation between particle and bulk properties
has also been investigated. Since the EDEMTM software does not yet contain a code to calculate porosity
changes and pore water pressure (without coupling with CFD), this is implemented during a second step.
The final target of this study is to use the DEM software to possible modify Miedema and Evans analytical
solutions for sand and rock cutting at 3000 m water depths, but in the future the modelling of erosion could
also be a topic of research.
The current research consisted of becoming acquainted with the software and carrying out basic tests to
verify the outcomes. During the research it emerged that the shape of the particles determines whether the
expected behaviour of sand can be replicated. Also the relation between micro and macro properties, i.e. the
static friction of particle and the angle of internal friction, was investigated. Using a particle consisting of a
number of spheres with an irregular shape did give very good results. Passive earth pressure simulations
gave a very good match with the analytical solution, as did cutting tests in dry sand with a number of
cutting angles. Using a cutting angle of 90 degrees resulted in the occurrence of a wedge in front of the
blade with a wedge angle corresponding to literature.