Simulations of quasi-statically deforming granular materials : applications to the modelling of broken-ice fields

The objective of this thesis was to determine, by means of discrete element simulations of ice floes, information that could be used for continuum modelling of broken ice covers on waterways. The ice floes or 'particles' were modelled as random-sized circular disks. The internal angles of friction for cohesionless assemblies of particles under compression were determined using molecular dynamics type simulations of biaxial tests. Constant confining pressures as well as constant displacement rates were used for the biaxial tests. Stress-strain curves were obtained for a range of confining pressures. The yield envelopes were found to be represented by a Mohr-Coulomb failure criterion. The effect of the interparticle friction coefficient on the global angle of friction was examined. It was found that the internal angle of friction was essentially independent of the interparticle friction angle. Furthermore, assemblies with different particle size distributions were used in order to investigate the effects of this parameter on the internal angle of friction. It was found that as the particle size distribution is made wider, the magnitude of the internal angle of friction increases. Angle of repose simulations were performed in order to verify the internal angles of friction results. It is found that the angles of repose measured are in rough agreement with, but slightly higher than, the values found for the internal angles of friction in the biaxial tests. Finally, biaxial tests were performed on assemblies in which bonds were introduced between the particles in order to simulate an intact ice cover. Results were consistent with a cohesive Mohr-Coulomb material