[en] An experimental identification of the hydro-mechanical behaviour of an argillite rock is proposed within a multi-scale approach. In particular, interest is focused on the spatial and temporal localization of strain and damage in a specimen during hydro-mechanical loading. Firstly, we describe the techniques used to follow the rock evolutions under loading, and in particular Digital Images Correlation (DIC), Acoustic Emission, microscopy and mercury intrusion porosimetry. Measurement errors and device limitations are discussed. The studied material is the Callovo-Oxfordian indurated argillaceous rock (or argillite) of the Bure site where ANDRA has built an underground research laboratory to study the radioactive waste storage. Petrophysical characterizations and microstructural observations by optical and scanning electron microscopy provide an identification of the constitutive phase and a characterization of their spatial distribution and typical sizes. Argillite can be described as a composite structure with a continuous clay matrix and embedded mineral particles, essentially quartz and carbonates. The typical size of these particles ranges from a few micrometers to a few hundreds micrometers, with an average close to 50 μ.m. The general experimental procedure combines two steps: in a fist time, imposed suctions bring samples to a given degree of water saturation, and, in a second time, uniaxial mechanical compression tests are performed. To understand the evolutions of the material under hydric and mechanical loading, samples are instrumented with standard measurement techniques, but also with Digital Image Correlation, at both the global scale of the sample and the local scale of the composite microstructure, and with Acoustic Emissions recording. Moisture transfers are imposed by controlled suctions on the range of 150 to 2.8 MPa, corresponding to the relative humidity range of 32 to 98%RH. During pure hydric solicitation, the changes in physical parameters (weight, longitudinal and transverse strains) are continuously recorded until stabilization. When sample equilibrium is reached, uniaxial compressive tests are performed. Samples brought to lower relative humidity undergo an anisotropic shrinkage associated with a water content decrease. Samples in equilibrium at 98%RH swell and store water. Depending of the clay ratio, a significant contribution to this swelling can be shown to be due to the opening of these preexisting cracks and to the creation of new cracks. The macroscopic mechanical response and in particular its linearity and the spatial homogeneity of the strain distribution, depend on the initial rock microstructure (clay ratio) and on the microstructure induced by the suction (new crack network). When suction increases from 2.8 to 150 MPa, Young modulus and strength increase with a factor respectively close to 2 and 3. For dry states, macroscopic strain fields are homogeneous while at the microstructure scale, strain are heterogeneous and clearly correlated with the local distribution of mineral constituents; clayey areas are more deformable than other mineral phase. For wet states, overall and local strain fields are heterogeneous. Strain are affected by the presence of the cracks: close to them, local strain are important but at a distance from cracks large than a few hundreds micrometers, strain distributions are similar to those in the dry states. The main behaviour difference between dry and wet states seems to be due more to the presence of cracks induced by the suctions, than to an intrinsic evolution of the mechanical properties of the clay matrix. The multi-scale quantification of strain heterogeneity by Digital Image Correlation, and the determination of the damage appearance by Acoustic Emission, are useful input data for the development and validation of multi-scale constitutive models for argillite. (author)

No abstract available

[en] During the construction and the exploitation phase of the waste disposal, and after its closure, the rock mass will be submitted to various thermo-hydro-mechanical loadings. The rock, initially saturated, will partially de-saturate due to the ventilation of the galleries. The drying could generate tensile stresses at the galleries wall; however drying will also increase the rock strength and the creep strain rate will be made slower. In order to predict the short-term and long-term responses of the rock, laboratory experiments are conducted to build models and to determine the corresponding parameters which will be used to perform predictive numerical simulations. The hydro-mechanical models must be able to describe the transition between the saturated and unsaturated states. This paper deals with the modelling of some aspects of the unsaturated hydro-mechanical behaviour and transport properties of this argillite on the basis of the interpretation of laboratory experiments performed at different relative humidities

[en] The ventilation in underground galleries during the exploitation phase of a radioactive waste disposal will induce an unsaturated zone in the host rock. The suction gradient due to the drying can induce tensile stress which could modify the excavation damaged zone (EDZ). Such a situation has already been evidenced at Tournemire where tensile cracks occur due to the relative humidity changes. The purpose of the study is to investigate the effects of desaturation on Bure argillite samples submitted to decreasing relative humidity. (authors)

[en] In addition to direct mechanical perturbations, an excavation influences environmental conditions (hydraulic, thermal and chemical), which may strongly influence the physical properties of rocks. In particular, the modification of the internal fluid flows may drastically change their water content either by hydration or desiccation. The aim of the present study is to investigate the influence of the degree of saturation on the mechanical properties of shale rocks extracted from Andra underground research laboratory in Bure. (authors)

[en] The excavation of underground galleries is expected to create a damaged zone around the galleries. Additional damage could be induced by the desaturation-re-saturation due to the ventilation in galleries. Desaturation induced cracks have already been observed in the Tournemire shale (France) and break-up of shot-crete in the reconnaissance gallery has been caused by swelling of Opalinus clay (Switzerland) around borehole collars. The assessment of the damaged zone is of main importance to estimate the retention capacity of rock mass. The first step of understanding such as process consist s in studying the moisture transfer in rock samples, in order to access to the mass transfer kinetics and to the spatial extension of the unsaturated zone. (authors)

[en] The following topics were examined: (i) Methodology of fracture tests at temperature gradients and pressurized thermal shock (PTS) cooling tests on large specimens (1500x1200x140 mm) with a designed postulated crack and other smaller cracks in the cooled area (test performed on a ZZ 8000 (80MN) loading stand); (ii) simulation of radiation embrittlement of tested material near the end of the RPV designed life, the material is subjected to standard mechanical property tests and fracture tests of standard test specimens modelling the PTS regime of material loading; (iii) 100% NDT tests of a specimen before the beginning of tests and μTOFD before and after each particular test of a specimen; (iv) on-line monitoring of the test conditions based on instrumentation of a specimen with thermocouples, COD and strain gauges together with on-line monitoring of Acoustic Emission during the tests; (v) calculation of K_l at the critical points of the crack front during the test, based on monitored boundary conditions; (vi) fractographic analysis after the fracture of a specimen and evaluation of the whole test. (P.A.)

No abstract available

[en] This session gathers 30 articles (posters) dealing with: the three Dimensional analyses of combined gas, heat and nuclide transport in a repository considering coupled thermo-hydro geomechanical processes; the experimental study on the thermo-hydro-mechanical behaviour of boom clay; hydraulic in-situ measurements in the Opalinus clay in the frame of a heater test performed at the Mont Terri URL; the hydro-mechanical behaviour of natural boom clay in controlled-suction tests; a constitutive approach to address the thermal and hydric impacts in the concept of deep radioactive waste repositories; the numerical analysis on stability of boom clay tunnel by shield construction; a thermo-hydro-mechanical model for clay in unsaturated conditions; the 3D modelling of TER experiment accounting for fully anisotropic thermo-poro-elastic behaviour; the hydro-mechanical modeling of shaft excavation in Meuse/Haute-Marne laboratory; the modelling of drying damage in engineered and natural clay barriers for nuclear waste disposal; the elasto-viscoplastic behaviour of Meuse/Haute-Marne argillite: laboratory tests and modelling; the long-term behaviour of a lime treated soil under percolation conditions; the stress redistribution and hydro-mechanical effects due to excavation and drilling operations in TER experiment; a thermodynamic model on swelling of bentonite buffer and backfill materials; the 3D analysis of a heating test in the Opalinus clay; the THM analysis of a 'mock-up' laboratory experiment using a double-structure expansive model; the measurement of the effect of re-confinement on rock properties around a slot; a laboratory Study of desaturation - re-saturation effects on a clay-stone; the deformation induced by dissolution of salts in porous media; the bentonite swelling pressure in pure water and saline solutions; the mineralogy and sealing properties of various bentonites and smectite-rich clay materials; the evaluation of the geochemical processes occurring in the Opalinus clay formation subjected to a ventilation test; a Soil structure considerations in description of compacted and natural clay behaviour; the hydro-mechanical behaviour of Tunisian clayey soil used as discharge site of acidic waste; the Consolidation and rebound properties of Opalinus clay: a long-term, fully-drained test; the multidimensional modeling of a poro-elastic medium: identification of the behaviour of a clay formation from a stochastic representation of piezometric fluctuations; various approaches for the comprehension of the time-dependent behaviour of Callovo-Oxfordian argilite; a new approach of estimating the influence of drilling mud on the borehole pressure history; the thermo-chemical-hydro-mechanical modelling: contributions to the assessment of the long term behaviour of a nuclear waste disposal in a deep clay formation; and the impact of thermal load on the far field and galleries of a repository