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International audienceThis modelling study deals with the time-dependent behaviour of rockfill media, which is of particular interest during the life of rockfill dams. Breakage of rock blocks and crack propagation are the main processes responsible for rockfill creep and collapse. The modelling procedure presented here is performed on two scales: on the rock block scale, where the grain is taken to be an assembly of rigid particles initially endowed with cohesive bonds, and on the rockfill scale, which is taken to involve a set of breakable grains interacting via contact and friction processes. The grain breakage process is described in term of a thermodynamically consistent damage interface model, where the damage is a gradual delayed process. This model was implemented in a non-smooth contact dynamics code. The effects of the main parameters involved were analysed by performing numerical studies. The ability of the model to predict the creep behaviour of rockfill media is confirmed by presenting several simulations

Geosynthetics are used as reinforcing elements in a wide variety of structures: reinforced slopes and walls; embankments on soft soils; piled embankment; reinforcement in the base layers of railroad and road constructions; reinforced foundation mattresses; bridging of sinkholes or reinforced abutments. In some cases, these reinforced structures require anchorage areas. Designing the required dimensions of this anchorage remains problematic. This paper focuses on the simple run-out and wrap around anchorages. Laboratory tests, performed with these two anchorage benches, consisted of the pull-out of three geotextiles (uniaxial or biaxial with different stiffness) anchored following various geometries in different kinds of soil. In order to confirm and to complete the experimental studies presented in these anchorage systems, a specific two-dimensional discrete-element model has been used. The soil was described by discrete elements and the geosynthetic behaviour was taken into account by the use of thin finite elements. The interface behaviour between the soil particles and the geosynthetic elements was considered at each contact point by using a Coulomb contact law. The numerical model reproduced the experimental campaign and the anchorage mechanisms reasonably. The load transfer between the geosynthetic and soil was visualised by the force and displacements distribution along the geosynthetic sheet. The numerical procedure could also be used to define the conditions of stability for reinforced slopes or walls.

Old tunnels suffer from deterioration and it is necessary to assess their residual strength to properly organize their repair and strengthen them. The stress state of underground structures evolves over time, firstly because of the advancement of the working face during construction, then due to gradual changes in soil properties and mechanical properties of materials composing the infrastructures, such as reduction of cohesion, loss of strength and (or) stiffness, etc. These changes are caused by combined actions such as creep and (or) weathering processes as well as the appearance of cracks that induce redistribution of stresses and therefore strains. This study investigates tunnels and galleries of the Paris underground. Macromodeling based on the finite element method allows consideration of different scenarios of tunnel-lining deterioration, specifically at the extrados of the galleries or tunnels. To understand changes in the stress state, and also damage occurrence and associated redistributions (stress and strain), it is necessary to model the delayed deformations. To model the infrastructure behavior, a time-dependency approach has been chosen. This approach can quantify the damage and predict the residual strength of this type of underground structure. An elastic–viscoplastic constitutive model with strain-softening is used to reproduce the appearance of the degraded zones and their behavior. The results obtained with the numerical approach reproduce Paris metro tunnel behavior, corroborate geoendoscopy results, clarify their interpretation, and improve the management of infrastructure repairs.

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