Rockfill are made by coarse materials, blocks, whose size can reach one meter. Rockfill dams, composed by these blocks, show some relatively important deformations during time and during their filling or during an accidental flood. These deformations seems to be related to blocks ruptures in the inner structure, but they are unfortunately unknown after the dam construction.The settlements' prevision is then particularly important to ensure the structural integrity of the dam in a long time.The granular media behaviour is strongly related to the discrete nature of the medium. A discrete model is proposed to take into account rockfill particularities with local parameters that have clear physical sense. Ruptures are rockfill major features. The major idea in this work, consisted in developing a numerical discrete model to account for progressive and delayed blocks failure. Each block is considered as an assembly of particles with initial cohesive bonds which can decrease progressively during the loading. A damaging interface model is proposed to describe this progressive phenomenon. The model is composed by two yield surfaces (damage and fracture yield surfaces). A characteristic time is related to the damage evolution. The water influence is introduced by couplage with the parameters of the cohesion model, by decrease of the wedge and of the local friction. The modelling adopted is based on the “Non Smooth Contact Dynamics Method”, where grains and particles are rigid. The model is implemented on the discrete element code, LMGC90.Numerical simulations are realised at contacts, block and rockfill scales. First simulations consisted in modelling an assembly of unbreakable blocks disposed in a rockfill column and progressively filled by water. Simulations reveal that the buoyancy forces and the diminution of the local friction produce only low displacements in the medium. These simulations verify that blocks fracture is the major phenomenon responsible of the settlements of rockfill dams.Simulations of compression of breakable blocks and oedometric compression of an assembly of these blocks are realised. Results show that bonds ruptures and deformations are well correlated. Numerical simulations of oedometric compression tests composed by rockfill reveal some creep and relaxation responses. These tests reproduce the basic phenomena with only few parameters.
展开▼
