The effect of mesh size on 3D finite element collapse settlement analyses for a large dam

3D finite element analyses of the construction of and subsequent impounding behind a large central clay core embankment dam in a steep sided valley are carried out. Collapse settlement in the upstream rockfill due to the rising reservoir is included in the modelling, which incorporates first a linear elastic and then a critical state elastoplastic model. The analyses are repeated for a "coarse" and a "medium" mesh with the principal object of assessing the effect of the mesh refinement. Secondary objectives were to find out what is involved in a complex three dimensional simulation such as this and to comment on the engineering significance of the findings. It was found that the mesh size did not significantly affect the results. The suitability of the procedures was confirmed and the particular suitability of the critical state model highlighted. One interesting result is the ability of this model to reproduce localisation of strain in the core near the crest of the dam similar to what has been observed.