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This paper describes the development and application of inflow and outflow boundary conditions (BCs) for the material point method (MPM) in order to simulate fluid flow problems. This corresponds to velocity and pressure controlled BCs. Due to the coupled Lagrangian and Eulerian description of the fluid motion in MPM it is necessary to add and remove material points, with appropriate kinematic properties, to and from the computational domain. The newly-developed BCs have been used to simulate uniform open channel flow and the phenomenon of free overfall in open channels, which is transient conditions leading to non-uniform flow due to a sudden bed level drop. It is shown that the numerical results predict well the flow geometry including end depth ratio, pressure distribution and accelerations, therefore the velocities and displacements.

This paper presents the results of an experimental 1 and numerical investigation on the collapse of dykes involv-2 ing soft soils. Nine centrifuge tests were carried out to in-3 vestigate the dyke-subsoil interaction. The tests consisted in 4 placing a dyke made out of Speswhite clay or Baskarp sand 5 on a subsoil. The dykes and the subsoils were alternatively 6 changed to explore the different contrast in stiffness ranging 7 from stiff dykes on soft subsoil to soft dykes on stiff sub-8 soils. The small scale models were placed in the centrifuge 9 and were progressively accelerated up to a maximum of 100 10 G. The video recordings, which were then processed by Par-11 ticle Image Velocimetry (PIV), offered an insight onto the 12 deformation and failure mechanisms. The results showed 13 that dykes placed on a stiff subsoil underwent brittle fail-14 ures with the development of slip surfaces whereas the same 15 dyke placed on a soft subsoil underwent large deformation 16