SUMMARYThis paper presents a new constitutive model for the time dependent mechanical behaviour of rock which takes into account both viscoplastic behaviour and evolution of damage with respect to time. This model is built by associating a viscoplastic constitutive law to the damage theory. The main characteristics of this model are the account of a viscoplastic volumetric strain (i.e. contractancy and dilatancy) as well as the anisotropy of damage. The latter is described by a second rank tensor. Using this model, it is possible to predict delayed rupture by determining time to failure, in creep tests for example. The identification of the model parameters is based on experiments such as creep tests, relaxation tests and quasi-static tests. The physical meaning of these parameters is discussed and comparisons with lab tests are presented. The ability of the model to reproduce the delayed failure observed in tertiary creep is demonstrated as well as the sensitivity of the mechanical response to the rate of loading. The model could be used to simulate the evolution of the excavated damage zone around underground openings.

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A simplified model for calcium leaching in concrete is presented. It is based on the mass balance equation for calcium in the porous material. This model is implemented in a Finite Volume code and validated by comparison between numerical simulations and experimental results found in the literature, for cement pastes and mortars as well as for concretes, with a satisfactory agreement. Then, a parametric survey has been performed. It enlightens the large influence of porosity and diffusivity on the leaching kinetic. In complement, a large experimental campaign, which aims at acquiring data on the material characteristics variability (within several batches for a same concrete mix design) has been undertaken. This campaign investigates porosity and the degradation depth at different times considering accelerated leaching under variable temperature. Nevertheless, the coefficient of tortuosity (which partially controls diffusivity in concrete) cannot be directly measured, although it is an important parameter to model the calcium diffusion process. Therefore, an inverse identification tool is developed and validated, based upon

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SUMMARYDamage induced by microcracking affects not only the mechanical behaviour of geomaterials but also their hydraulic properties. Evaluating these impacts is important for many engineering applications, such as the safety assessment of radioactive waste disposal facilities. This paper presents a new constitutive model accounting simultaneously for the impact of damage on hydraulic and mechanical properties of unsaturated poroplastic geomaterials. The hydro-mechanical coupling is formulated by means of the thermodynamic framework for partially saturated media, extended by taking into account isotropic damage and plasticity. State and complementary laws are governed by the so-called plastic effective stress and equivalent pore pressure. Assuming a bimodal pore size distribution for cracked porous media, the hydraulic part (water retention curve and hydraulic conductivity) is modelled using phenomenological functions of damage variable. The participation of damage on both mechanical and hydraulic part enables this model to describe bilateral couplings between them. This coupled model is then validated against a number of experimental data obtained from Callovo-Oxfordian argillite, which is the possible host rock for a radioactive waste disposal in France. Parametric studies are also carried out to check the consistency and to better demonstrate the bilateral couplings in the model.

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