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A sensitivity study is presented to evaluate the influence of different parameters on the simulation of an underground excavation in the Callovo-Oxfordian (COx) argillaceous formation performed in the Meuse/Haute-Marne underground research laboratory. An elasto-viscoplastic constitutive law representing the characteristic behaviour of indurated mudrocks and stiff clays has been employed. It incorporates anisotropy, strain-softening, creep deformations and dependence of permeability on damage. In addition, a non-local formulation, able to simulate localised deformations objectively, has been incorporated in the analyses. The following features affecting the excavation have been studied: initial stress, strength and stiffness anisotropy, strength parameters, hydraulic and hydromechanical parameters, and scale effects. A simulation reported in a companion paper provides the base case for benchmarking. The results are compared in terms of extent and configuration of the excavation fractured zone, vertical and horizontal tunnel convergences, and the development and evolution of pore pressures in the rock. From the comparisons, an enhanced understanding of the hydromechanical mechanisms associated with underground excavations in COx claystone, and other similar argillaceous materials, has been achieved. We are grateful for the financial and technical assistance of the French national radioactive waste management agency (Andra) to the work presented. The technical assistance of Plaxis is also gratefully acknowledged. The first author has been supported by a Conacyt scholarship (Reg. No. 270190).

This work aims at investigating the effect of aleatoric uncertainty of creep rock properties on the stability of an underground structure. This uncertainty relates to the spatial variability of the mechanical parameters representing the time-dependent behavior of geological rock formation due to the change in its mineralogy. The chosen methodology consists of representing the aleatoric uncertainty of rock properties by random fields, written as correlation functions with respect to the spatial correlation length. The adaptation of the well-known Expansion Optimal Linear Estimationmethod (EOLE) is performed to account for the cross-correlation of the random fields of the viscoplastic parameters of the host rock. Then, the Kriging-based reliability analysis is undertaken with respect to the discretized random fields, which allows elucidating the effect of spatial variability. As an application, the proposed approach is chosen to study the stability in the long-term of a deep double-lined drift within the geological disposal facilities (Cigeo project) conducted by the French National Radioactive Waste Management Agency (Andra). The drift will be excavated in Callovo-Oxfordian (COx) claystone (if the Cigeo project is licensed), considered as a potential host rock for the deep geological nuclear waste disposal in France. The results show that the chosen Kriging metamodel for the reliability analysis can be appropriate for the case of high correlation length represented by a moderate number of random variables (up to about 50) after the discretization of random fields. Further, the consideration of aleatoric uncertainty exhibits a lower probability of exceedance in comparison with the case where spatial variability is ignored. Still, more investigations need to be conducted in the future to conclude this observation.

In the 1980s, HADES (High-Activity Disposal Experimental Site) was the first underground research laboratory (URL) dedicated to the study of the geological disposal of radioactive waste in a deep clay formation, the Boom Clay. It was not until the early 2000s, after a siting process, that ANDRA implemented the Meuse/Haute-Marne URL, in the Callovo-Oxfordian formation at a depth of about 500 m in order to develop the Cigéo project (French industrial centre for geological disposal). ANDRA therefore relied heavily on the work carried out in HADES, through numerous co-operation projects (participation in in situ experiments) both between ANDRA and ONDRAF/NIRAS and SCK CEN (EURIDICE) and/or with Mont Terri consortium, and within European projects (CLIPEX, RESEAL, etc.). This was driven by a dual objective: (1) to prepare its own experimental programmes in the Meuse/Haute-Marne underground laboratory (methodology, experimental devices and protocols, etc.); and (2) to acquire general knowledge on the behaviour of argillaceous rocks, in particular in terms of similarity and differences between the various argillaceous rocks. This paper illustrates the contribution of HADES to the ANDRA programme. This concerns the characterization of the claystone behaviour, host rock and swelling clay-based seals (hydromechanical, thermo-hydromechanical, excavation damaged zone, etc.), and the design and the behaviour of underground structures and seals in deep clay formation (constructability, lining/support, etc.).

Demonstrating the feasibility of constructing tunnels in deep clay formations is an important goal of the Belgian RD&D programme on the geological disposal of radioactive waste. In 2002 a major achievement was reached when the HADES Underground Research Laboratory (URL) in Boom Clay was extended with the construction of the Connecting Gallery. This demonstrated that it is feasible to construct galleries in poorly indurated clays using industrial techniques. To monitor the mechanical behaviour of the gallery and assess its stability, strain gauges were embedded in the segmental gallery lining and prisms were installed on the segments. These sensors provide valuable information that will support the design of future galleries. This paper presents 20 years of monitoring data in the Connecting Gallery and a first analysis of these data in terms of Boom Clay behaviour. In addition, the key findings are compared with those of a similar analysis performed by Andra (the French Radioactive Waste Agency) at the Meuse/Haute-Marne URL. The latter URL is excavated in the Callovo-Oxfordian claystone. The comparison identifies general trends and highlights similarities between the behaviour of tunnels in poorly indurated clay (Boom Clay) and in claystone.

This work aims at proposing the methodology on the basis of the extension of the famous reliability analysis, joining the Kriging and Monte Carlo Simulation (AK-MCS) metamodeling technique for analyzing the long-term stability of deep tunnel support constituted by two layers (a concrete liner covered with a compressible layer). A novel active learning function for selecting new training points enriches the Design of Experiment (DoE) of the built surrogate. This novel learning function, combined with an appropriate stopping criterion, improves the original AK-MCS method and significantly reduces the number of calls to the performance function. The efficiency of this modified AK-MCS method is demonstrated through two examples (a well-known academic problem and the case of a deep tunnel dug in the rock working viscoelastic Burgers model). In these examples, we illustrate the accuracy and performance of our method by comparing it with direct MCS and well-known Kriging metamodels (i.e., the classical AK-MCS and EGRA methods).

To assess the operational capacity of human resources in maternal and child health services, in order to provide equitable and sustainable universal health coverage in Benin, the Workload Indicators of Staffing Need (WISN) study was conducted. Method: A total of 487 health facilities and public hospitals were sampled, representing 75% of the public health facilities. Health professionals involved in maternal and child health care were exhaustively included. Results: Overall, 487 health facilities with 3,870 human resources of all categories were evaluated for their workloads. The analysis shows that the country does not have the necessary manpower to handle the workload. The time spent by the health professional on activities changes according to the type of activity. Finally, it is noted that there is work pressure on health professionals which changes according to the type of activity. Discussion: The shortage situation leads to inequity in the distribution of human resources and is a reason for allocative and technical inefficiency. It is observed that qualified human resources devote little working time to the main activities, which explains the observed high morbidity and mortality rates, particularly for mothers and children. In conclusion, the analysis of the results shows that the pressure of work is greater in rural areas than in urban areas for the professional categories most encountered in rural areas and that the health system is fragile in the country.

International audience; The thermo-hydro-mechanical behavior of the host rock is essential while designing an underground radioactive waste disposal repository, and in particular, while considering the long-term safety of the facility. In 2000, the French National Radioactive Waste Management Agency (Andra) started constructing an underground research laboratory located in the Meuse Haute Marne to carry out a research program aiming to demonstrate the feasibility of constructing and operating a radioactive waste disposal facility in the Callovo-Oxfordian claystone, and to optimize its implementation. To study the thermo-hydro-mechanical effects of the early thermal phase on the clay host rock of a deep repository, Andra has performed various in situ heating tests; one of them is called the TED experiment. The aim of the TED experiment was to measure the evolution of the temperature and pore pressure fields around several heaters and to back-analyze the thermo-hydro-mechanical properties of the Callovo-Oxfordian claystone. Thermal conductivity and heat capacity values were determined based on the back-analysis of the in situ measurements and compared to those measured on samples. The in situ experimental data and numerical model confirm the anisotropic behavior of the claystone. The TED experiment results demonstrate the ability of current models to predict the evolution of temperature and pore pressure in the far field of disposal cells.

The Meuse/Haute-Marne Underground Research Laboratory (MHM URL) is an outstanding scientific tool that provides reliable data on the behaviour of Callovo-Oxfordian (COx) claystone. More than 10,000 sensors have been installed in the argillaceous formation to measure rock properties and behaviour under several configurations in order to assess coupled processes. Since 2004, data have been acquired continuously through several measurement campaigns –mainly in galleries at the main level, −490 m (clay unit level –, i.e. UA level), but also in a gallery at −445 m [silty carbonate unit level (USC)]. This experiment has increased understanding of the hydro-mechanical behaviour of claystone and highlight various phenomena. The research program carried out in the MHM URL galleries also is dedicated to technology improvement and demonstration issues of several disposal systems. 1 At MHM URL, the principal horizontal major stress ( σ H ) is oriented at NE150° , and the principal vertical stress ( σ v ) is nearly equal to the principal horizontal minor stress ( σ h ) that is oriented NE065° . The ratio σ H ∕ σ h is close to 1.3 and varies with depth and the rheological characteristics of the respective layers. This paper presents the hydro-mechanical coupling (i.e. interaction between the interstitial water and the solid skeleton) during and after excavation work. The influence of the in-situ stress fields on several types of support was studied for a gallery oriented according to the principal minor horizontal stress ( σ h ). This paper presents an analysis of measurements recorded during and after the construction of an experimental gallery, referred to as the GER, from 2013 to 2015. The GER experimental gallery is an 83-m-long tunnel, in which four different supports were tested: sliding arches; shotcrete; compressible wedges; and poured concrete. Sliding arches, shotcrete and compressible wedges constitute the initial supports that were installed during excavation. The poured concrete was set up about 9 months after the section excavation as a final support, first at the bottom and then at the vault of the gallery. Hydrogeological and geotechnical measurements help to describe the hydro-mechanical response of the surrounding rock mass. Experimental results highlight the anisotropy of the loading from the surrounding rock mass and the influence of the stiffness/flexibility of the support.

Anisotropic mechanical properties of the sedimentary Callovo-Oxfordian clay rock were investigated with triaxial compression and extension, cyclic compression, and creep tests. The tested cylindrical samples differ in bedding orientation. The compression was accomplished by increasing axial stress at constant radial stress. The extension was carried out vice versa: radial stress was increased while axial stress was kept constant. Moreover, extension was also achieved by simultaneously increasing radial stress and decreasing axial stress under constant mean stress. Five independent elastic parameters were obtained at different deviatoric stresses during cyclic loading-unloading compressions. The deformation and strength were determined in relation to the load direction inclined to bedding and in relation to the load paths. The claystone exhibits elastoplastic stress-strain behaviour with volume compaction until failure. The strength is dependent on both load path and load direction to the bedding. For a given major load direction, the compressive strength is higher than the extensional one and the lowest strength occurs by extension at constant mean stress. In each load path, the maximum strength values are reached parallel and normal to the bedding, while the minimum occurs at the load orientation of about 45° during compression and of about 30° during extension. The elastic stiffness increases with deviatoric loading due to hardening. The deformability is time dependent.

The Andra’s (French National Agency for Radioactive Waste Management) Meuse / Haute-Marne Underground Research Laboratory in Bure is currently under extension (4th extension), with the excavation of new galleries having different shapes and support types. The galleries are excavated in the Callovo-Oxfordian (COx) claystone, with a creeping behaviour, at 490 m depth. The continuum rheological model which has been considered (among the available ones) is an elasto-visco-plastic model with the Hoek-Brown failure criterion and the Lemaitre creep law. The choice of the rock parameters to be used for the design studies of the 4th extension (aiming to verify the stability of support systems over a service duration of 20 yr) has been based on two sets, defined in previous studies and calibrations. The in-situ measurements, provided by the R&D division of Andra, of three galleries and a shaft, excavated about 10 yr ago, have been back-analysed with these two sets of parameters. The comparison of results led to the choice of the most suitable set of parameters for the design of the new extension galleries.

In France, a deep geological disposal for high-level radioactive waste (HLW) and intermediate level long life radioactive waste (IL-LLW) called Cigéo is planned to be constructed in a deep Callovo-Oxfordian claystone (COx) formation, if it is authorized. The heat emitted from the waste leads to a temperature increase in the low permeability host porous formation, which induces a pore pressure increase essentially due to the difference between the thermal expansion of the pore water and the solid skeleton. This study aims at assessing the effect of nonlinear behavior of COx, especially creep, on the THM response of the HLW repository. Different approaches, from perfectly MohrCoulomb model and simplified time-dependent models (power and Norton) to an advanced model, have been considered. These approaches lead to common conclusions that (1) the creep reduces the pore pressure increase compared to poro-elastic approach; (2) the nonlinear instantaneous response in the near-field resulting from cell drilling does not affect the THM response in the far field and (3) the thermal load does not induce any supplementary damage of the host rock

In the context of feasibility study for geological disposal of radioactive waste, this work focuses on numerical modeling of hydromechanical response and induced damage zones around an experimental gallery at the underground research laboratory (URL) at Bure in France. A new phase-field method is first proposed by considering two independent damage fields in order to easily describe both tensile and shear cracks. The phase-field method is extended to saturated porous media by incorporating the effect of fluid pressure. The proposed method is implemented in a finite element code and applied to the experimental gallery. The evolutions of hydromechanical responses and induced damaged zones are analyzed in both excavation and post-excavation phases. Numerical results are compared with experimental observations and measurements. It is found that the proposed method is able to well describe the main features of hydromechanical responses and damage processes such as tensile and shear cracked zones.

In France, a deep geological disposal for high level radioactive waste (HLW) and intermediate-level long-lived radioactive waste (ILW-LL) called Cigeo is planned to be constructed in a deep Callovo-Oxfordian claystone (COx) formation. The heat released from the HLW packages leads to a temperature increase in the host rock, which causes a pore pressure increase essentially due to the difference between the thermal expansion of the pore water and the solid skeleton. The low permeability of the COx and its relative rigidity inhibit the discharge of the induced pressure build-up. Moreover, thermal loading also induces thermo-mechanical stresses within the formation. The French National Radioactive Waste Management Agency (Andra) participated in the DECOVALEX-2019 project (Task E) to model the Thermo-Hydro-Mechanical (THM) responses of a benchmark exercise inspired of a HLW repository based on the French concept. This paper aims at studying the THM behavior of the HLW repository by taking into account the inherent spatial variability of the properties of the host rock through thermo-poro-elastic numerical simulations. Only the most influential parameters were selected to perform the spatial variability analysis by using Monte Carlo simulations coupled with the Random Finite Element Method . The selection of the most influential parameters was based on two parametric sensitivity analyses consisting in computing the Sobol indices, which determine the contribution of each input parameter to the overall model output variance. The temporal evolution of the Terzaghi effective stress in the far field is defined as indicator of the influence of each parameter on the THM response.

Author(s): Seyedi, DM; Plua, C; Vitel, M; Armand, G; Rutqvist, J; Birkholzer, J; Xu, H; Guo, R; Thatcher, KE; Bond, AE; Wang, W; Nagel, T; Shao, H; Kolditz, O | Abstract: The coupled Thermo-Hydro-Mechanical (THM) behavior of the Callovo-Oxfordian claystone (COx) is of great importance for the design and safety calculations of the high-level radioactive waste disposal project in this potential host rock in France. The heat emitted by the waste causes a pore pressure increase within the surrounding rock essentially due to the differential thermal expansion of the pore water and the solid skeleton. The low permeability of the COx and its relative rigidity inhibits the discharge of the induced pressure build-up. Moreover, thermal loading may provoke thermo-mechanical stresses within the formation due to mechanical confinement by the rigidity of the surrounding host rock. An important research program has been conducted by the French National Radioactive Waste Management Agency (Andra) since 2003 in order to investigate the THM response of the COx under thermal loading, through laboratory tests, in-situ experiments, model development and numerical modeling. Within Task E of the DECOVALEX-2019 project, five research teams investigated upscaling THM modeling from a small-scale in-situ experiment (TED) to a full-scale in-situ experiment (ALC). The upscaling modeling started with a verification test to validate the numerical codes. Then, an interpretative modeling of the TED experiment was performed to calibrate the THM parameters of the COx. Finally, the calibrated THM parameters were used for a blind prediction of the ALC experiment. The modeling teams each adopted a thermo-poro-elastic approach which yielded satisfactory results. The blind prediction of the temperature field showed an overestimation of less than 2 °C which was considered acceptable. On the other hand, pore pressure was well predicted only in the direction parallel to the bedding whereas the slow dissipation of the pore pressure in the direction perpendicular to the bedding was not captured by any of the modeling teams – which remains an open question of the present study.

The French National Radioactive Waste Management Agency (Andra) is in charge of studying the disposal of high-level and intermediate-level long-lived waste (HLW and ILW-LL) in a deep geological repository (Cigéo project) within the host formation is the Callovo-Oxfordian claystone (COx). The heat emitted from waste packages induces a thermo-hydro-mechanical (THM) coupling within the structural elements and the host rock. This study focuses on the behavior of the concrete lining of an ILW-LL cell subjected to THM loading during its construction and operational phases. The mechanical behavior of the host rock is represented by an elasto-visco-plastic model taking into account the anisotropies in stiffness and strength. The coupled THM formulation is based on the Biot theory. Different simulations including full THM coupling and HM coupling with or without creep behavior of COx claystone have been performed to show the effect of the thermal load (generated by the waste packages), of the water seepage and of the creep strain of the host rock on the stress evolution in the concrete liner. The results show the preponderant role of the creep strain of COx claystone on the stress state of the liner during the operational phase, while the effect of the heat loading is moderate and that of the seepage is not significant.

International audience; Continuous monitoring around drifts excavated in the Underground Research Laboratory (URL) of The French National Radioactive Waste Management Agency (Andra) in Callovo Oxfordian claystone revealed the development of a fractured zone (extensional and shear fractures) induced by the excavation. Moreover, the field monitoring during the excavation showed an anisotropic pore pressure field around the drifts with zones of marked overpressure. For drifts parallel to the horizontal major principal stress, even though the initial stress state in the drift section is quasi-isotropic, the pore pressure evolution and the mechanical response are anisotropic. These observations suggest that the intrinsic anisotropy of the material plays a key role in the response of rock formation. A poroelastic analysis of the pore pressure change induced by drift excavation is performed. The principal objective is to simulate the main trends of the pore pressure evolution with a simple model taking into account the elastic anisotropy of the material. It is shown that depending upon the permeability and the degree of anisotropy of the rock, strong overpressures can be induced by the excavation. Furthermore, it is observed that the distribution of overpressures around drifts depends also on the drifts orientation. Finally, an analysis of the onset of failure shows the key role of the hydro-mechanical coupling on the extension of the failed zone around the drifts.

The Callovo-Oxfordian claystone (COx) is considered as a potential geological formation to host an industrial radioactive waste repository in France. A detailed understanding of the thermo-hydro-mechanical (THM) behavior of the COx is a key issue for design of different repository structures and the safety calculations of the project. More particularly, numerical modeling of induced fracture networks around drifts excavated at the main level of the Andra’s Meuse/Haut-Marne Underground Research Laboratory (M/HM URL) and short and long term behavior of the COx around these drifts are of great interest. Several constitutive models have been developed/used in the framework of the R&D and simulation programs of Andra. A model benchmark exercise has been launched since 2012 to provide an overall view of the developed models regarding the in situ observations. In this view, two series of test cases, respectively at material point scale and at drift excavation scale are defined. Different kinds of constitutive models based on the elasto-visco-plasticity concept, continuum damage mechanics, the rigid block spring method and two-scale computational homogenized model (CHM) are used within this exercise. The obtained results show that accounting for material anisotropy and strain localization treatment techniques can improve the obtained results when elasto-visco-plastic models are used. Damage mechanics based approaches and methods accounting for discontinuities through discrete elements provide also interesting insights especially when fracturing processes must be modeled. However, more efforts are necessary to improve the robustness of these kinds of approaches in the complex context of COx response to excavation works.

This paper addresses the microstructure change induced by swelling for natural stiff Teguline clays. The predominant clay mineral measured by X-ray diffractometry was identified to be illite and no swelling clay minerals were found. Significant swelling occurs upon wetting, illustrating the process of suction release from a nearly fully saturated condition. Mercury intrusion porosimetry (MIP) and scanning electron microscopy were used to identify the change in microstructure with swelling during wetting. It is found that the soil swelling mainly leads to an increase of macropores (0.15–350 μm), and a slight decrease of micropores (0.006–0.15 μm) and inaccessible pores (350 μm). Furthermore, swelling was found to occur in the direction perpendicular to the bedding plane, indicating an anisotropic swelling behaviour. The creation and development of cracks during wetting were also investigated. It appears that most cracks caused by swelling have the size of macropores (0.15–350 μm) identified by the MIP test. These findings call enough attention to the significant change in microstructure by wetting-induced swelling that can strongly influence the thermohydromechanical properties of stiff clays.

This paper is devoted to the study of the Thermo-Hydro-Mechanical (THM) responses of a porous rock with low permeability under thermal loading in the context of deep geological disposal of radioactive waste. To this aim, numerical simulations of a benchmark exercise of a hypothetical high-level radioactive waste (HLW) repository were performed. This benchmark exercise considered as a host formation the Callovo-Oxfordian claystone (COx), which has been selected for a deep geological disposal in France. Within the framework of the DECOVALEX-2019 project, five modelling teams (Andra, LBNL, NWMO, Quintessa, UFZ/BGR) adopted a thermo-poro-elastic approach and proposed different 3D representations of the HLW repository. The differences between the teams consisted mostly in the simplification of the geometrical model and the interpretation of the boundary conditions. Numerical results for temperature, pore pressure , and effective stress evolution in the far field (i.e., at the mid-distance of two HLW cells) were compared between the teams, to quantify the impact of modelling simplifications/assumptions for the assessment of the HLW repository. The THM behaviour of the COx formation in the near field (i.e., excavation damaged zone around the HLW cells) is not the objective of this study. Moreover, plane strain conditions were considered and evaluated in comparison to 3D modelling. Key parameters influencing the THM responses of the HLW repository were assessed by both mono- and multi-parametric analyses. Spatial variability analyses of THM parameters were also carried out to study the influence of the spatial correlation length on the Terzaghi effective stress and to estimate its probability distribution. The conclusions of this study provide reliable numerical techniques for modelling large-scale deep geological disposals and deduce the main behavior of the HLW repository.

This study is part of numerical simulations performed on an in situ heating test conducted by the French National Radioactive Waste Management Agency (Andra) at the Meuse/Haute-Marne Underground Research Laboratory (URL) to study the thermal-hydromechanical behavior of the host Callovo-Oxfordian COx claystone in quasi real conditions, through the international research project DECOVALEX. The emphasis is put on the pore pressure increase generated by the heat released from high level radioactive waste and the consequence on the damage evolution of the host rock. A phase-field method is proposed to describe the evolution of damaged zones around the heating borehole. Both tensile and shear cracks are taken into account. The evolution of damage is coupled with temperature variation, rock deformation, and fluid pressure change. Moreover, the structural anisotropy of elastic properties, permeability, and heat conductivity of the host rock is taken into account. Numerical results are compared with in-situ measurements.

Within the context of deep geological radioactive waste disposal, the French National Radioactive Waste Management Agency (Andra) is conducting a research program including in-situ experiments at the Meuse/Haute-Marne Underground Research Laboratory (MHM URL), which aims to demonstrate the feasibility of constructing and operating a High Level Waste (HLW) disposal facility in the Callovo-Oxfordian (COx) claystone formation and to improve it. ALC1604 experiment is an in-situ heating test reproducing a full-scale HLW disposal cell. Heating devices were placed in the last 15 m of a 25 m long steel cased micro-tunnel to mimic the heat emitted by the HLW packages. The present experiment allows to study the response of the cell and the surrounding rock under thermal loading. More specifically, this experiment studied the thermo-mechanical (TM) behavior of the steel sleeve, equipped with strain gauges, displacement sensors, temperature sensors, etc., and monitored the evolution of the annular space (the gap between the sleeve and the rock). It also studied the thermo-hydro-mechanical (THM) behavior of the near/far field rock through pore pressure and temperature measurements installed in peripheral boreholes. The TM response of the steel sleeve and the THM response of the surrounding rock are numerically reproduced and the chosen THM parameters are compared with previous small-scale in-situ experiments conducted at the MHM URL in order to improve the reliability of the material parameters of the COx. The lessons learned from this experiment has provided valuable feedback towards implementing new full-scale heating experiments consistent with a new benchmark concept. DECOVALEX is an international research project comprising participants from industry, government and academia, focusing on development of understanding, models and codes in complex coupled problems in sub-surface geological and engineering applications; DECOVALEX-2019 is the current phase of the project. The authors appreciate and thank the DECOVALEX-2019 Funding Organizations Andra, BGR/UFZ, CNSC, US DOE, ENSI, JAEA, IRSN, KAERI, NWMO, RWM, SÚRAO, SSM and Taipower for their financial and technical support of the work described in this report. The statements made in the report are, however, solely those of the authors and do not necessarily reflect those of the Funding Organizations. The experimental work presented in this article has received funding from the European Atomic Energy Community's Seventh Framework Program under Grant Agreement n◦269905, the LUCOEX project. The financial support is gratefully acknowledged.

This paper summarises the numerical and experimental studies of brittle, hollow, cylindrical particles, called shells. It addresses the influence of shell properties both at the particle and assembly scales. Extreme compressibility has been recorded in the oedometer tests. Due to the large internal porosity of the shell, the breakage phenomena lead to highly compressive deformations with a significant stress dissipation. Using the Discrete Element Method (DEM), we have investigated in depth the micro-mechanical phenomena governing this macroscopic response. By quantifying the breakage and separating the double-porosity of the material, the foundations of a future constitutive model have been established throughout a simple prediction model applicable to the engineering practice.

Author(s): Xu, H; Rutqvist, J; Plua, C; Armand, G; Birkholzer, J | Abstract: We apply thermoporoelasticity and a sequentially coupling technique for modeling thermally-driven coupled Thermo-Hydro-Mechanical (THM) processes in tight claystone. A THM benchmark case with a corresponding analytic solution for thermoporoelasticity under a constant heat loading verifies the model. Thereafter, two in situ heating experiments are simulated for model validation: a smaller-scale heating experiment (TED experiment) and a larger-scale experiment (ALC experiment) in Callovo-Oxfordian (COx) claystone at the Meuse/Haute-Marne underground research laboratory in France. The model exhibits good performance to match the observed temperature and pore pressure evolution for the smaller-scale TED experiment. For the larger-scale ALC experiment, general trends of thermal-pressurization are captured in the modeling, but pressure is underestimated at some monitoring points during cool-down. This indicates that the THM response in the field may be affected by the variability of rock's properties or irreversible or time-dependent mechanical processes that are not included in the current thermoporoelastic model. The main contributions of this work are as follows: (1) we verify and validate the numerical simulator, TOUGH-FLAC, to be a valuable coupled THM modeling tool; (2) prove that the laboratory determined material parameters can be used as reference values for upscaling experiments. However, to better identify and quantify THM processes with modeling of in situ tests, more emphasize should be dedicated to obtaining high-quality mechanical deformation data.

This study focuses on highly compressible granular material incorporated in novel tunnel-lining technology, precisely, the prefabricated tunnel segments called voussoirs. The material composed of hollow, brittle, tube-shaped particles were designed such that the crushing of the constituent particles results in high material compressibility. This paper is essentially dedicated to discrete-element simulations that involve both the breakage of the particles at micro scale and the resulting effects on macro scale. Firstly, a 3D model was proposed in order to adequately reflect the complex geometry and the breakage manner. In applied strategy, the tube-shaped particle is modelled as a cluster of bonded, rigid, sphero-polyhedral sectors. Then, the identification of the parameters that control the mechanical response and the strength of the particles is presented using a radial compression test. This step was supported by laboratory experimental tests. Finally, six assemblies of cluster under oedometric loading were studied by means of Discrete Element numerical simulations. We analysed the influence of the sample size on the evolution of particles breakage and void ratios. This analysis resulted in the definition of new framework for void ratio and a model capable of predicting breakage as a function of the strains.

Les epoux B. demandent au tribunal de condamner le conseil general de l’Eure a reparer le prejudice moral subi par eux-memes et par leur fille ainee a l’occasion du suicide de leur fille cadette. Cette derniere, confiee a l’aide sociale a l’enfance du departement a la suite de fugues repetees, s’etait enfuie de l’hopital ou elle etait soignee apres une tentative de suicide. Violee lors de cette fugue par des pensionnaires d’un autre foyer departemental de l’enfance, elle se suicide apres avoir ete auditionnee dans le cadre de cette affaire. Le rapporteur public, apres avoir rejete la prescription quadriennale invoquee par le defendeur, conclut a la responsabilite du conseil general de l’Eure et demande au tribunal de le condamner.

International audience; The main purpose of this paper is to analyze the convergence measurements in drifts of the Underground Research Laboratory (URL) of the French National Radioactive Waste Management Agency (Andra), excavated in Callovo-Oxfordian claystone. These measurements show an anisotropic closure, which depends on the drift orientations with respect to the horizontal in situ stresses. This anisotropic character of the deformation is taken into account by assuming that the drifts section evolves following an elliptical shape. The characteristics of the deformed elliptical section are evaluated following the methodology proposed by Vu et al. (Rock Mech Rock Eng 46:231–246, 2013). Then, using the semi-empirical law proposed by Sulem et al. (Int J Rock Mech Min Sci Geomech Abstr 24:145–154, 1987), the convergence evolution is fitted independently for each axis of the ellipse. This method allows to distinguish two effects: the face advance and the time-dependent behavior of the ground. The results for the two drift orientations (along the major horizontal stress and perpendicular to it) show very close values for the parameters describing the time-dependent properties of the ground, the distance of influence of the face, and the extent of the decompressed zone around the drift. Finally, the model is validated by keeping these parameters as constants and by simulating the convergence data on a new drift. It is shown that with a period of about 40 days of convergence monitoring, the model can provide valuable insights for predictions of the convergence evolution in the long term.

Summary The Excavation Damaged Zone (EDZ) surrounding a drift, and in particular its evolution, is being studied for the performance assessment of a radioactive waste underground repository. A specific experiment (called CDZ) was designed and implemented in the Meuse/Haute-Marne Underground Research Laboratory (URL) in France to investigate the EDZ. This experiment is dedicated to study the evolution of the EDZ hydrogeological properties (conductivity and specific storage) of the Callovo-Oxfordian claystone under mechanical compression and artificial hydration. Firstly, a loading cycle applied on a drift wall was performed to simulate the compression effect from bentonite swelling in a repository drift (bentonite is a clay material to be used to seal drifts and shafts for repository closure purpose). Gas tests (permeability tests with nitrogen and tracer tests with helium) were conducted during the first phase of the experiment. The results showed that the fracture network within the EDZ was initially interconnected and opened for gas flow (particularly along the drift) and then progressively closed with the increasing mechanical stress applied on the drift wall. Moreover, the evolution of the EDZ after unloading indicated a self-sealing process. Secondly, the remaining fracture network was resaturated to demonstrate the ability to self-seal of the COx claystone without mechanical loading by conducting from 11 to 15 repetitive hydraulic tests with monitoring of the hydraulic parameters. During this hydration process, the EDZ effective transmissivity dropped due to the swelling of the clay materials near the fracture network. The hydraulic conductivity evolution was relatively fast during the first few days. Low conductivities ranging at 10–10 m/s were observed after four months. Conversely, the specific storage showed an erratic evolution during the first phase of hydration (up to 60 days). Some uncertainty remains on this parameter due to volumetric strain during the sealing of the fractures. The hydration was stopped after one year and cross-hole hydraulic tests were performed to determine more accurately the specific storage as well as the hydraulic conductivity at a meter-scale. All hydraulic conductivity values measured at the injection interval and at the observation intervals were all below 10–10 m/s. Moreover, the preferential inter-connectivity along the drift disappeared. Specific storage values at the observation and injection intervals were similar. Furthermore they were in agreement with the value obtained at the injection interval within the second hydration phase (60 days after starting hydration). The graphical abstract synthesizes the evolution of the hydraulic/gas conductivity for 8 intervals since the beginning of the CDZ experiment. The conductivity limit of 10–10 m/s corresponds to the lower bound hydraulic definition of the EDZ and it is demonstrated that EDZ can be sealed. This is a significant result in the demonstration of the long-term safety of a repository.

This paper provides new empirical evidence concerning the relationship between human capital (measured by education and health related variables) and economic growth for a large sample of 49 African countries over the period from 1996 to 2010. Using traditional cross-section and dynamic panel techniques, we find that public expenditures on education and health have a negative impact on economic growth, whereas human capital stock indicators have a slight positive effect. Furthermore, our empirical investigations suggest that education and health spending are complementary. Then, public investment in education and health should be jointly increased and their efficiency in order to expect positive impact of human capital on growth in African countries.

Since 2000, the French National Radioactive Waste Management Agency (ANDRA) has been constructing an Underground Research Laboratory (URL) at Bure (east of the Paris Basin) to perform experiments in order to obtain in situ data necessary to demonstrate the feasibility of geological repository in the Callovo-Oxfordian claystone. An important experimental program is planned to characterize the response of the rock to different drift construction methods. Before 2008, at the main level of the laboratory, most of the drifts were excavated using pneumatic hammer and supported with rock bolts, sliding steel arches and fiber shotcrete. Other techniques, such as road header techniques, stiff and flexible supports, have also been used to characterize their impacts. The drift network is developed following the in situ major stresses. The parallel drifts are separated enough so as they can be considered independently when their hydromechanical (HM) behaviors are compared. Mine-by experiments have been performed to measure the HM response of the rock and the mechanical loading applied to the support system due to the digging and after excavation. Drifts exhibit extensional (mode I) and shear fractures (modes II and III) induced by excavation works. The extent of the induced fracture networks depends on the drift orientation versus the in situ stress field. This paper describes the drift convergence and deformation in the surrounding rock walls as function of time and the impact of different support methods on the rock mass behavior. An observation based method is finally applied to distinguish the instantaneous and time-dependent parts of the rock mass deformation around the drifts.

The performance and safety assessment and technology demonstration are the main objectives of research programs for feasibility studies for deep geological repository of radioactive waste. In this context, the French national radioactive waste management agency (ANDRA) started to develop the Meuse/Haute-Marne underground research laboratory (URL) at Bure, nearly 300 km East of Paris. The host formation consists of a Callovo-Oxfordian claystone found between 420 and 550 m below ground, overlain and underlain by poorly permeable carbonate formations. One of the major concerns related to performance assessment is the excavation-induced fractures which may provide groundwater preferential pathway for radionuclide migration. The extent of the fractures possibly acting significantly in the radionuclide migration is known as the excavation damaged zone (EDZ). A scientific study on the EDZ characterization is performed at the main level of the URL (−490 m). Observations such as structural analysis on core, overcored resin-filled samples, geological survey of the drift face and sidewalls, were made to better understand the fracture network characteristics, extent and its generation. Pulse and constant head test hydraulic conductivity measurements were performed with multi packer system to estimate the extension of the EDZ hydraulic conductivity. Fractures exhibited high transmissivity near the excavation walls, but farther from the exaction walls, shear fractures showed hydraulic conductivity values reflecting values of undisturbed or slightly disturbed rock mass condition. The major findings in terms of geometry and properties of excavation-induced fractures are discussed in detail in this paper. For example, it is observed that the shape of the fracture network depends on the orientation of the drift in relation to the orientation of the in situ stress field.

La loi du 16 juin 2011 relative a l’immigration, a l’integration et a la nationalite, qui opere la transposition de la directive 2008/115/CE du Parlement europeen et du Conseil du 16 decembre 2008 relative aux normes et procedures communes applicables dans les Etats membres au retour des ressortissants de pays tiers en sejour irregulier, modifie singulierement le regime de la retention administrative des etrangers, ce qui impacte les garanties constitutionnelles de leur liberte individuelle et, dans le meme temps, prevoit un systeme nouveau de repartition des competences entre les juridictions administratives et judiciaires, dont il convient de mesurer les consequences du point de vue des garanties juridictionnelles de la liberte individuelle des non-nationaux.

The French National Agency for Nuclear Waste Management is currently studying the Callovo-Oxfordian claystone as a potential repository for nuclear waste. This study focuses on the hydromechanical (HM) unsaturated response of the rock subjected to hydraulic loading. Static atmosphere drying tests highlighted the HM coupling and mechanical anisotropy of the samples. A coupled poroelastic model was proposed, involving highly nonlinear equations. Numerical simulations were performed using the finite element code Code_Aster. Through a sensitivity analysis, the most suitable parameters for estimation were found to be the Biot coefficient and 3 of the 4 independent parameters of the Van Genuchten–Mualem relations. The parameters were estimated according to an inverse procedure that minimizes a cost functional. The estimates could not outline any hysteretic behavior, but they appeared to be divided into two groups (depending on their fitted values). The convergence and stability of the inverse algorithm were studied, and the results showed that direct computations must be run prior to the inversion to ensure its convergence. No plasticity occurred in the samples (according to the model), whereas irreversible phenomena do take place in situ.

In order to investigate potential changes of the hydraulic properties of the EDZ over time in the Meuse/Haute-Marne underground research laboratory (URL), several hydraulic tests campaigns have been carried out between 2005 and 2008 in dedicated boreholes. After several test series, inconsistencies were noticed in the results, indicating, in particular cases, erratic, inexplicable property changes over time and spatial contrasts. It was therefore difficult to determine reliably potential trends of the EDZ hydraulic properties. It appeared necessary to re-evaluate both the interpretation concepts and assumptions applied to the numerical analyses of test data on the EDZ, trying to better constrain the flow model and the parameter variables. In order to improve the understanding of the geometrical, geomechanical and hydraulic properties of the EDZ, independent information from other investigation methods has been used to critically revise the conceptual model and formation parameters. In particular, results from a diffusion experiment and ultrasonic measurements allowed constraining the extent of the mechanical damaged zone around the borehole (BDZ). Storativity parameters were fitted due to their expected variability. Indeed, high storativity values can be presumed under the unsaturated conditions of the EDZ. The results of the reanalyses, performed with the numerical borehole simulator MULTISIM, demonstrated the good quality and consistency of the revised conceptual model with constrained BDZ and variable storativity. Overall the new simulation results obtained from selected test series are now very consistent. The revised conceptual model demonstrated its capacity to better represent the evolution and extension of the EDZ around a drift in Meuse/Haute-Marne URL. Further consistency checks are proposed to confirm the new model assumptions and the estimates of the single phase flow model in the EDZ.

The excavation of a deep underground structure induces a stress field redistribution that could create an excavation-damaged zone (EDZ). The study of the EDZ is important in the framework of nuclear waste storage, where such EDZ could constitute a preferential pathway of stored material towards the biosphere. Analysis of ultrasonic wave propagation across the rock media around the excavation is one technique that can be used to characterize such zones. This method has been applied in the Meuse/Haute-Marne Underground Research Laboratory (URL) in France to characterize the initialization and evolution of damage around the URL access shaft. To achieve this, a device comprising 21 ultrasonic sensors was spread out at different distances from the shaft wall, at depths between -465 and -475 m. A transversely isotropic model enabled the measured experimental velocities on each ray path during shaft excavation to be integrated. The results highlighted the initialization and extension of the damage as the shaft front proceeded. They also showed a polarization of the velocity field and an oscillation of the transversal isotropy with a preferential orientation of the stress release and the microcracking. Monitoring of the velocity field also highlighted some significantly different behaviour linked to the complex mechanical behaviour of the argillaceous rock.

The Meuse Haute Marne underground research laboratory of Meuse (ANDRA) is constituted by several shafts and drifts. The whole of the laboratory is mainly located in a volume of several millions cubic meters in the Callovo–Oxfordian geological layer. The shafts and the various drifts form a complex structural design. In order to see possible interference between drifts and shafts and to assess the in situ stresses in specific areas of the laboratory, a numerical study was performed to model the mechanical behaviour of the whole drifts by using a chronological sequence of the excavations, close to what was actually realised. Numerical modelling, with considering the geometric scale of the problem, was carried out by finite elements with relatively simple constitutive models describing the argillites. It is on the one hand a linear isotropic elastic model and on the other hand a nonlinear modified associated elastic-perfectly plastic Drucker–Prager model. The different numerical problems were solved within the infinitesimal strains and displacements framework. The finite elements are tetrahedrons (with quadratic basis) which imply more than 2.5 × 10 6 degrees of freedom. The main interest of such a modelling on a large scale, even using a simple constitutive model, is to measure and analyse the evolution of various mechanical fields such as stresses, strains and displacements, during the time evolution of the laboratory. The excavation was performed in 26 steps based on monthly excavation rate performed in situ. The greatest displacements are located in the vicinity of the shaft at the main level of the laboratory, where the cross section is biggest. The areas concerned by shaft–drift or drift–drift intersections are also places of high stress and strain concentration. The area disturbed by the excavation of the shafts is relatively wide. The perturbations induced by the excavation propagated preferentially in a radial direction. However, the zone of extension is relatively restricted such as the plasticity zones. This explains the observation that in the “radial” direction, the influence of the excavation decrease in O (1/ r ) for the displacement and in O (1/ r 2 ) for the strain and stress. Thus beyond a given distance, different parts of laboratory work mechanically in a quasi independent manner.

In November 1999 Andra began building an Underground Research Laboratory (URL) on the border of the Meuse and Haute-Marne departments in eastern France. The research activities of the URL are dedicated to study the feasibility of reversible, deep geological disposal of high-activity, long-lived radioactive wastes in an argillaceous host rock. The Laboratory consists of two shafts, an experimental drift at 445 m depth and a set of technical and experimental drifts at the main level at 490 m depth. The main objective of the research is to characterize the confining properties of the argillaceous rock through in situ hydrogeological tests, chemical measurements and diffusion experiments. In order to achieve this goal, a fundamental understanding of the geoscientific properties and processes that govern geological isolation in clay-rich rocks has been acquired. This understanding includes both the host rocks at the laboratory site and the regional geological context. After establishing the geological conditions, the underground research programme had to demonstrate that the construction and operation of a geological disposal will not introduce pathways for waste migration. Thus, the construction of the laboratory itself serves a research purpose through the monitoring of excavation effects and the optimization of construction technology. These studies are primarily geomechanical in nature, though chemical and hydrogeological coupling also have important roles. In order to achieve the scientific objectives of this project in the underground drifts, a specific methodology has been applied for carrying out the experimental programme conducted concurrently with the construction of the shafts and drifts. This methodology includes technological as well as organizational aspects and a systematic use of feedback from other laboratories abroad and every scientific zone of the URL already installed. This methodology was first applied to set up a multi-purpose experimental area at 445 m depth. Then the setting up of the experimental programme at the level 490 m was improved from the knowledge acquired during installation of the drift at 445 m. The several steps of the underground scientific programme are illustrated by presenting three experiments carried out in the underground drifts. The first experiment was carried out from the drift at 445 m depth, from end of 2004 to mid 2005. This experiment aimed at setting up an array of about 16 boreholes to monitor the geomechanical changes during and after construction of the shaft between 445 and 490 m. The second experiment was set up in the drift at 445 m depth, and also at the main level at 490 m depth. It consisted in determining the composition of the interstitial water by circulating gas in one borehole and water of a known composition in the other. The evolution of the composition of both water and gases enabled us to test the thermodynamic model of the water/rock interactions. The third example is related to the testing of a concept of interruption of the EDZ through a cross-cut slot technology. The concept, which was tested successfully at Mont Terri (Switzerland), has been transposed and adapted to the URL site conditions. The results will be used for developing a concept for drift sealing.

During gallery excavation, regardless of the method chosen, the surrounding rock is mechanically disturbed in the case of a an underground disposal (for ultimate chemical wastes or for radioactive wastes), such mechanical changes to the rock state can create preferential pathways for releasing material from the waste inside the excavation (e.g. chemical waste gases, brine or dissolved radionuclide) up to the biosphere. The mechanical characterization of this disturbed zone is thus essential to assessing the rock capacity necessary for constituting an impermeable geological rock barrier. The key to this effort lies in determining the nature, extent and change to this disturbed zone. The survey by means of ultrasonic wave analysis is particularly appropriate for these purposes since it provides information on the zone left undisturbed by the boreholes. The main objective behind this paper is to describe a recent in situ experiment (called EZ-A) conducted in Opalinus clay at the Mont Terri Rock Laboratory in Switzerland (Bossart et al., 2002). This in situ experimental campaign successfully studied the possibility of improving the properties of rocks forming the EDZ (Excavation Damaged Zone). The experiments consisted of three stages: the first entailed locating the EDZ from the existence of gallery EZ-A at the Mont Terri laboratory; the second traced evolution of the EDZ arising from a 20-cm thick and 150-cm deep slot excavation at the EZ-A gallery floor; and the third stage focused on P-wave velocity evolution surrounding the slot during a pressure loading performed at the slot walls, which serves to characterize EDZ evolution in the slot. These three stages were carried out by applying the seismic technique of tomography and then recording wave propagations during the excavation and reloading stages. The velocity before and after slot excavation reloading, along with the survey during slot excavation, showed a decrease in P-wave velocity underneath the slot floor down to a 0.2 m depth. Reloading clearly improves P-wave propagation along the sidewall and slightly decreases these same characteristics under the slot.

Andra, the French national radioactive waste management agency, is in charge of studying the possibility of disposal of High Level activity Wastes (HLW) in deep geological repositories. The concept of HLW cells consists of horizontal micro-tunnels of about 0.7 m in diameter, equipped with a steel casing. In order to ensure the reliability of the casing, particularly with respect to Stress Corrosion Cracking (SCC), several in-situ experiments dedicated to the analysis of its short term mechanical and corrosion behavior have been performed at Andra’s Underground Research Laboratory (URL) as well as in surface laboratory. Reduced and full scale in-situ experiments consisting of equipping boreholes parallel to the major horizontal stress (σH) with instrumented steel tubing, have been performed to analyze the mechanisms involved in the casing/rock interface. The main characteristics of the short term mechanical load applied by the rock have been determined from local strain and convergence measurements. Although in-situ stress is isotropic in the section of boreholes parallel to σH, measurements exhibit a strongly anisotropic load. SCC experiments conducted on different steel grades, in contact with the clay host rock containing CO2/H2 revealed that general corrosion is the main type of corrosion expected for steel casings. However, the selected steel casing must have a sufficiently high yield strength (above 400 MPa) to reduce the risk of early stage plasticity due to host rock anisotropic convergence and thus to overcome SCC. API5LX65 steel seems to meet both mechanical and corrosion requirements, therefore being likely the appropriate material for the manufacture of the casing.

In this paper, the propagation of both longitudinal and surface waves will be investigated within the scope of seismic measurements recorded along the circumference of concave structures. The underlying objective herein is to recover, in a non-destructive manner, the mechanical material properties from seismic refraction as well as multiple-channel analysis of surface wave measurements. This experimental set-up along the circumference is currently employed in the case of circular concrete tunnels or shafts when sensors cannot be installed along the structural baseline. The influence of curvature on longitudinal wave propagation will first be quantified by means of a simple analytical model. If curvature is neglected, the thickness of a damaged concrete cover will be overestimated, whereas its longitudinal wave propagation velocity will be underestimated. For surface waves, it will be shown that the influence of curvature exerts a major impact on phase velocity, which cannot be incorporated into the classical multiple-channel analysis of the surface wave forward problem. Consequently, we have developed a numerical model dedicated to such geometries that relies upon complex values of the surface wave phase velocity. The first part of this article is dedicated to the description of the mathematical derivation of the propagation of surfaces wave in a curved medium. This numerical model is then compared with experimental data recorded on a reduced-scale concrete tunnel of metric size. The agreement between experimental and numerical results, as well as seismic refraction and the multiple-channel analysis of surface wave complementarity, form the basis of an in situ, non-destructive testing technique.

G. A. : En premier lieu, pourriez-vous rappeler, s’il vous plait, l’apport historique de la loi de 1905 en ce qui concerne le rapport entre les Eglises et l’Etat en France ? Et, j’ajouterai : peut-on considerer que cette loi a constitue un tournant ou simplement la poursuite d’un mouvement de laicisation enclenche depuis la Revolution de 1789 ? J. B. : Je vais commencer par la fin et je vais remonter au debut de votre question. Effectivement, la loi etait presentee a l’epoque comme parachevan...

La construction de tunnels a faible profondeur, en site urbain alluvionnaire, a l'aide d'un tunnelier, vise un mouvement aussi limite que possible du bâti existant, et donc un deconfinement reduit du sol concerne. Apres une presentation sommaire de la section de tunnel (metro de Lyon Vaise) examinee, les auteurs analysent l'histoire du chargement du complexe sol-tunnel, correspondant aux diverses phases des travaux. Ils proposent ensuite une modelisation en elements finis 2D de l'ensemble du processus de creusement et soutenement, inspiree des principes du calcul inverse, pour le premier tube, puis pour l'ensemble des deux tubes. Ils evaluent enfin la pertinence de cette demarche par comparaison aux calculs executes selon la methode de deconfinement d'une part, et au vu des resultats d'auscultation de la section d'autre part.

The French national radioactive waste management agency (Andra) research program is dedicated to preparing the construction and operation of a deep geological disposal facility for high-level and intermediate-level long-lived radioactive waste (HL, IL-LLW) in the Callovo-Oxfordian claystone (COx). The characterization of the COx thermo-hydro-mechanical (THM) behavior, at different scales of interest, must gradually give relevant data for design and safety calculations. The effects of saturation and desaturation of COx claystone are studied in laboratory conditions (sample scale) and in situ (drift scale), in order to improve knowledge on ventilation effect at gallery wall as galleries will remains open during operational phase (more than 100 years for some specific galleries) in the repository. The Saturation Damaged Zone (SDZ) experiment is outlined and its results are discussed. This experimentation aims to change the relative humidity in an isolated portion of a gallery in order to follow the HM behavior of the surrounding rock mass. Drying and wetting cycles could induce in certain cases cracks and swelling and modify the hydromechanical behavior of the claystone around the gallery (Young modulus, strength, creep…). The long term behavior of the COx claystone at the vicinity of gallery is then studied by performing climatic, hydraulic, geological and geomechanical measurements. Results of the in situ experiment are discussed with respect to the identified process on samples. The discussion given on this paper intends to highlights the inputs from 7 years of an in situ experiment to better understand the unsaturated behavior of the COx claystone.

Within the framework of the feasibility study for a radioactive waste repository in a geological formation, the National Radioactive Waste Management Agency of France is constructing an underground research laboratory within the Callovo-Oxfordian argillite formation located in eastern France. During the sinking of the laboratory's access shaft and during excavation of the galleries, the mechanical and hydromechanical behavior of the argillite was monitored. A vertical mine-by test was carried out at depths between 460 m and 476 m in the main shaft. 12 boreholes were drilled downwards from a niche, where deformations and pore pressures were monitored. Another 11 boreholes were instrumented with mechanical and hydraulic sensors in the galleries. This paper is devoted to the instrumentation, the installation procedures and some first measurement results regarding the mechanical disturbance of the rock around the shaft.