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Grgic, D. (Université de Lorraine, CNRS, GeoRessources) | Giraud, A. (Université de Lorraine, CNRS, GeoRessources) | Moumni, M. (Université de Lorraine, CNRS, GeoRessources) | de La Vaissière, R. (ANDRA, RD960, 55290 Bure) | Talandier, J. (ANDRA, RD960, 55290 Bure)
ABSTRACT: This study presents complex series of laboratory permeability tests in which both steady state and pulse decay methods were applied on core samples of the weakly permeable Callovo-Oxfordian claystone from Bure (France). The focus was to explain why permeability values obtained in laboratory with the steady state method are lower than those obtained with the pulse decay method and those obtained in-situ, and to assess the impact of these measurements on the mechanical properties. The intrinsic permeability values measured with the steady flow method are homogeneous and range between 1.2×10 and 7.5×10 m. They are significantly lower than those obtained from the pulse decay method (~10 m) and from in-situ measurements. This could be explained by an additional hydration of the clay minerals during steady state flow and the associated swelling, which decrease the interparticle porosity and slow down the water flow. The steady flow permeability tests induce a significant damage of the material which is mainly due to the opening of the bedding planes of swelling clay minerals (smectites). An accurate assessment of the permeability of a claystone with the steady state method requires a chemically equilibrated water and experiments with short run time. 1. INTRODUCTION The Callovo-Oxfordian (COx) claystone in Meuse/Haute-Marne (France) has been chosen to host the Underground Research Laboratory (URL), located 500 meters underground in Bure and managed by ANDRA (National Agency for the Management of Radioactive Waste), for a feasibility study of a deep geological repository of radioactive waste due to its very low permeability. In the particular case of radioactive waste disposal management, knowledge of permeability is very important because it controls fluids transfers. COx claystone is a very low permeable rock whose permeability has been widely studied in the past two decades. Permeability measurements on core samples have been performed parallel and perpendicular to the stratigraphy and over the entire thickness of the argillaceous formation in French laboratories with different techniques: interpretation of water profiles from water sorption/desorption isotherms, diffusion tests with tritiated water, tests in triaxial cell under steady (stationary/permanent) or transient (pulse decay test) flow regime. In-situ results were also obtained through a series of tests (short-term hydraulic/packer tests, long-term pressure monitoring, long term pumping tests with argon) carried out in deep boreholes from the surface and short boreholes in the Meuse/Haute-Marne Laboratory. In-situ measurements have the great advantage to be carried out under hydraulic and mechanical conditions relatively close to natural conditions, but difficult to control (Delay et al., 2006). Laboratory measurements on core samples allow the control of a wide range of experimental conditions (e.g., pressures, stresses, temperature…) despite the difficulties related to sampling and conditioning.
Abstract We have a plan to publish a book titled "Stress and stress fields in geomechanics" by François Cornet, Tatsuya Yokoyama, and Tsuyoshi Ishida. This will be published as part of the Geomechanics Research Series by Taylor & Francis Group, CRC Press/Balkema. Until just before he passed away, François worked very hard on the book and often reminded us of the work still ahead. After he passed away, we found that he left his manuscript corresponding to 80 % of his original plan. At that time, we believed that we could publish the book almost as originally planned by adding our missing sections and in accordance to his family's wish. In this paper, we share the table of contents of the future book and our plan ahead. Introduction We have a plan to publish a book titled "Stress and stress fields in geomechanics" by François Cornet, Tatsuya Yokoyama, and Tsuyoshi Ishida. This book will be published as part of the Geomechanics Research Series by Taylor & Francis Group, CRC Press/Balkema. After François got his geological engineering degree in France, he entered a master's program at the University of Minnesota, USA in September 1969, and stayed for a Ph.D. under the supervision of Prof. Fairhurst (Cornet, 2019). Figure 1 shows a photo of Prof. Fairhurst with several of his former students including François. The first time that Tsuyoshi Ishida saw François was just after the 1995 ISRM Congress in Tokyo, when he and Prof. Emmanuel Detournay visited Prof. Yoshiaki Mizuta at Yamaguchi University. Prof. Yoshiaki Mizuta was one of François' friends and Tsuyoshi was an associate professor in his laboratory at that time. Because Tsuyoshi had stayed at the University of Minnesota for one year in 1993–1994, he has already heard many good things about François. Tsuyoshi's first impression of François was that the man was great fun. After that, Tsuyoshi met François at many symposiums and other venues. During such opportunities, François often kindly invited Tsuyoshi to lunch or dinner. In 2012 when Tsuyoshi and his wife visited François in Strasbourg, François was very hospitable despite of his busy time just after coming back from a business trip and just before leaving for the University of Minnesota.
Cornet, J. S. (Meuse/Haute-Marne Underground Research Laboratory) | Plua, C. (Meuse/Haute-Marne Underground Research Laboratory) | Jaber, J. (Meuse/Haute-Marne Underground Research Laboratory) | de La Vaissière, R. (Meuse/Haute-Marne Underground Research Laboratory) | Zghondi, J. (Meuse/Haute-Marne Underground Research Laboratory) | Renaut, C. (Meuse/Haute-Marne Underground Research Laboratory) | Armand, G. (Meuse/Haute-Marne Underground Research Laboratory)
ABSTRACT: The Meuse/Haute-Marne Underground Research Laboratory (MHM URL) is a scientific tool intended to support the design and development of the French deep geological disposal facility for radioactive waste Cigéo. It provides in-situ data on the hydromechanical behavior of underground openings in the Callovo-oxfordian claystone (COx) to design and optimize the construction and operation of Cigéo. Tunnel intersections are singular structures where construction must be carefully monitored to guarantee operational safety. This URL exists since 2000 but only T shaped intersections have been excavated until now. The excavation of the first X shaped intersection will occur in 2021. Five installation phases, following the excavation steps, are planned to set up the instruments that will monitor the hydromechanical behavior of the COx. The acquired data comes from direct observations (geological surveys and convergence measurements) and from embedded sensors (deformation and pore pressure measurements). Different sensors, from extensometers and inclinometers to fiber optics and deformation gauges, will be installed. A multi-physical assessment of the fracture network around the intersection will lead to its characterization. Preliminary results, data acquired during excavation, show that the COx behaves partly as predicted by existing models but that it is influenced by an existing drift in its vicinity. 1. Introduction For more than two decades, the French national radioactive waste management agency (Andra) has been conducting research programs at the Meuse/Haute-Marne Underground Research Laboratory (MHM URL) to support the development of the French deep geological repository for intermediate level long-life (ILW-LL) and high-level (HLW) radioactive waste, Cigéo project. The first in-situ experiments have been conducted to characterize the Callovo-Oxfordian claystone (COx) properties and its response to excavation (Delay et al. 2014, Armand et al., 2017). New experiments have then been made to consolidate the design and assess design options and technological solutions. The Cigéo Project, whose license application will be submitted in 2021/2022, will be operated during at least 100 years after its commissioning and safe operations must be guaranteed during this time span. Cigéo basic design outlines different kinds of drifts (access drifts, disposal vaults, technical drifts …) but also many drift intersections. Tunnel intersections are known in all underground works as singular structures, due to their geometry and associated stress concentrations. This is especially true for X shaped intersections of tunnels of the same size. The MHM URL exists since 2000 but only T shaped intersections have been excavated until now. A special effort is therefore under way to characterize the hydromechanical behavior of the claystone around an intersection shaped in X. The in-situ data acquired during the excavation of the intersection will support the optimization of design and construction methods for the Cigéo project.
Prioul, Romain (Schlumberger-Doll Research) | Desroches, Jean (Rocks Expert) | Gaucher, Emmanuel (Karlsruhe Institute of Technology) | Bérard, Thomas (Schlumberger) | Doan, Mai-Linh (Univ. Grenoble Alpes, Univ. Savoie Mont Blanc) | Lecampion, Brice (Geo-Energy Lab, Ecole Polytechnique Fédérale de Lausanne (EPFL)) | Beauducel, François (Université de Paris)
ABSTRACT: François Henri Cornet was Emeritus Professor at the Institut de Physique du Globe de Strasbourg, France and the author of the book "Elements of Crustal Geomechanics." Sadly, he passed away suddenly on May 23, 2020 in Strasbourg. He was well known to the ARMA community and was the MTS keynote speaker at the 2017 ARMA symposium in San Francisco. He was a PhD advisor, close colleague, and friend to many of us, and will always be remembered as a passionate leader and mentor with a big voice and laugh, always ready to engage in scientific discussions and a true expert on stress field evaluation. Among other things, he was the main inventor of the HTPF (Hydraulic Testing of Pre-existing Fractures) method for full stress tensor determination. At the time of his passing, he was working on his second book with co-authors called "Stress and stress fields in geomechanics." In this paper, we revisit François's main scientific contributions to the geomechanics and geophysics communities. His main research interests spanned many topics: hydraulic fracturing and in situ stress measurements, understanding and modeling of regional stress fields, induced and natural seismicity, rock-fluid interactions, development of new observations techniques, advocate of large scale natural geophysical laboratories (e.g., Le Mayet-de-Montagne, Soultz-sous-Forêts, Tongonan, Corinth Rift Laboratory, nuclear waste disposal and carbon storage sites), and new modeling techniques for volcanology. 1 Introduction François Henri Cornet was Emeritus Professor at the Institut de Physique du Globe de Strasbourg, France and the author of the book "Elements of Crustal Geomechanics" (Cornet, 2015b). Sadly, he passed away suddenly on May 23, 2020 in Strasbourg. He was well known to the ARMA community and was the MTS keynote speaker at the 2017 ARMA symposium in San Francisco (Cornet, 2017). He was a PhD advisor, close colleague, and friend to many of us, and will always be remembered as a passionate leader and mentor with a big voice and laugh, always ready to engage in scientific discussions and a true expert on stress field evaluations. Among other things, he was the main inventor of the HTPF (Hydraulic Testing of Pre-existing Fractures) method for full stress tensor determination. At the time of his passing, he was working on his second book with co-authors called "Stress and stress fields in geomechanics" (Cornet et al., 2021), the original table of contents of which will be presented in a companion paper at the conference.
Duarte, Leandro (ICube Laboratory, Strasbourg, France) | Dellinger, Guilhem (ICube Laboratory/ENGEES, Strasbourg, France) | Dellinger, Nicolas (ICube Laboratory, Strasbourg, France) | Vazquez, José (ICube Laboratory/ENGEES, Strasbourg, France) | Heme-De-Lacotte, Luc (TechnipFMC) | Tcherniguin, Nicolas (TechnipFMC)
Abstract Currently, most of offshore platforms are equipped with gas turbines to fulfill their power requirement and consequently produce CO2 emissions as a by-product. The energy efficiency of the asset is a key factor in reducing their carbon footprint impact. Numerous ways can be considered within the process and utility systems to improve the energy balance. This paper will investigate the possibility to exploit the available hydraulic energy onboard offshore platforms to transform it into electrical energy. Part of the recoverable hydraulic energy is found in pressurized pipes where the flow is in charge or in other words under hydraulic pressure. The aim is to develop a novel turbine that will be optimized for water disposal energy recovery on offshore platforms. Hence the objective is to install a turbine to replace a conventional valve to maintain and regulate the pressure as well as generating electricity. In close collaboration with TechnipFMC, ICube laboratory (Strasbourg, France) is completing a development program for such an hydraulic turbine. This paper describes some outcomes of this comprehensive study performed by experimental engineers and researchers in the hydraulic discipline with the support of engineering integration by TechnipFMC.
ABSTRACT The Meuse/Haute-Marne underground research laboratory (URL) operated by the French national radioactive waste management agency (ANDRA) have conducted drift experiments in Callovo-Oxfordian claystone (COx), with extensive characterization of the excavation damaged zone (EDZ). Hybrid finite-discrete element method (FDEM) models were simulated as a proof-of-concept to understand if it can accurately predict the formation of the EDZ, and in doing so would provide insight into its evolution. Two cases were compared in this study, which are differentiated by the orientation of the tunnel relative to the horizontal principal stresses. The first case considered was when the drift was excavated parallel to the maximum horizontal principal stress (σH), and the latter was when the drift was excavated parallel to minimum horizontal principal stress (σh). The preliminary simulations were able to fairly predict the dominance of shear failure in the rock mass and overall fracture geometry around the excavation. However, due to simplifications made to the model leading to the absence of several inherent mechanisms in the experiment (i.e., rock bolts, intermediate principal stress, and confinement near the advancing face), the simulation generally overpredicts the extent of the EDZ. 1. INTRODUCTION Increasing global energy demand is a growing issue in modern society that is being addressed by different means of electricity production. In 2017, a quarter of the total energy production in Europe was generated using nuclear power, with France accounting for almost half of the production (Eurostat, 2020). The by-product of spent nuclear fuel is radioactive waste that will need to be properly contained and stored for long periods of time. Deep geological repositories (DGR) have been proposed as a solution for long-term nuclear waste storage in geological clay formations with favourable properties such as low permeability, low molecular diffusion, and excellent radioisotope retention capability (Armand et al., 2013). However, understanding the long-term structural integrity of the DGR must be verified through experiments and numerical simulation for it to be a feasible solution.
Tip: To find the desired paper in OnePetro, search for "EUROCK-2020-XXX", where "XXX" is the paper ID of the paper you are searching for. Meuse/Haute-Marne URL G. Armand C.C. Vu M. Figiel 095 Fractal dimension and lacunarity as measures of rock pores geometric complexity W. Sun 096 Fractal simulation of hydraulic fracturing in coal seam with cleats Z.Y. Hovgaard 149 Performance of a fully grouted GFRP rock bolt under combined pull and C.C. Li Antofagasta, Chile J. Arzúa J. González M. Cánovas J.T. Almenara 172 Rock support design in unlined pressure tunnels excavated in rock masses containing swelling minerals and slaking rock. Wattier 176 Roughness indices determination for fracture surfaces in Luxemburg S. Vandycke
Djizanne, H. (Andra, Meuse/Haute-Marne Underground Research Laboratory) | Armand, G. (Andra, Meuse/Haute-Marne Underground Research Laboratory) | Renaud, V. (Ineris, campus ARTEM) | Souley, M. (Ineris, campus ARTEM)
Underground Research Laboratories play an important role in the development of radioactive waste repositories in deep geological formations, from both scientific and technological standpoints. In this context, the French national radioactive waste management agency (Andra) has developed the Meuse/Haute-Marne Underground Research Laboratory (MHM URL) at Bure, about 225 km East of Paris. The host formation consists of a Callovo-Oxfordian (COx) claystone found between 420 and 550 m depth, surrounded by poorly permeable carbonate formations. The excavation worksite in the COx claystone is a scientific experiment in itself to characterise damage induced by excavation and support. Drift intersections are always complex structures due to their difficult design and construction. A specific experiment has been performed in the URL to study the intersection between two perpendicular drifts. Geotechnical and geological measuring equipment/surveys have been set up to study the rock mass deformations, and to complete the characterisation of the excavation-induced fractures around this drift intersection. The extent of fractures potentially significant for radionuclide migration is known as the Excavation Damaged Zone (EDZ). A scientific study on EDZ characterisation has shown 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. 3D modelling of the intersection of the GCR2 and GVA2 galleries was carried out using 2 constitutive models. Comparison of the computed plastic extensions for these two models provides better understanding of the complex geometry of excavation-induced fractures in intersection zones.
Abstract The French National Radioactive Waste Management Agency (Andra) is in charge of the study on the possibility of disposal for radioactive wastes in a deep claystone formation. A deep geological disposal facility 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 formation (COx), if licensed. In 2000, Andra began to build the Underground Research Laboratory (URL) at Meuse\Haute-Marne to (1) characterize the confining properties of the COx; (2) demonstrate the construability and working of the repository components and (3) optimize concept/design of the different components. Actually, several types of retaining structure have been constructed and instrumented in the URL to follow stress/strain evolutions, as well as better understanding of the interaction between the concrete structure and the surrounding rock. The lining stress measurement is a complicated measurement and often carried out indirectly from the strain measurement. One of the rare direct stress measurement is the flat jack technique, which provides a relatively simple and almost non-destructive punctual measurement of stress. Typically, the flat jack is withdrawn from the structure after the test and the structure is restored to the original state before the test. This is not the case in URL where the flat jack is kept in place, in a way to follow the stress time evolution by conducting regularly the test. This article proposes an interpretation method of flat jack measurement based on semi analytical methods and numerical modelling in a way to follow the time dependence evolution of orthoradial stress evolution in a tunnel lining. Those analysis have been conducted on measurements performed at URL. Comparisons with other measurements in URL were made to validate the proposed interpretation method. 1 Introduction In order to demonstrate the feasibility of a radioactive waste repository in claystone formation, Andra started in 2000 to build the URL at Bure (nearly 300 km east of Paris). The host formation consists of COx claystone, which exhibits very favorable conditions for repository of radioactive waste, as they generally have a very low permeability, small molecular diffusion and significant retention capacity for radionuclide. The objectives of the research program is to (1) characterize the confining properties of the clay; (2) test and optimize concepts at full scale on site (Armand et al. 2016). Among them, understanding the impact of excavation methods and the hydro-mechanical behavior of claystone on the support system of the drift at short and long term is a key issue for optimizing the support designs. Measurements/estimations of stresses evolution as function of time in the URL concrete structure is important to characterise the creep behaviour of surrounding rock and to design Cigéo lining structures.
Aoyagi, Kazuhei (Horonobe Underground Research Center) | Chen, Youqing (Kyoto University) | Ishii, Eiichi (Horonobe Underground Research Center) | Sakurai, Akitaka (Horonobe Underground Research Center) | Ishida, Tsuyoshi (Kyoto University)
Abstract In the excavation of a repository for high-level radioactive waste (HLW) disposal, the hydro-mechanical characteristics of the excavation damaged zone (EDZ) induced around the gallery wall must be understood because the EDZ can lead to the migration pathway of radionuclides. We performed herein a resin injection experiment at the 350 m gallery of Horonobe Underground Research Laboratory in Japan to investigate the characteristics of the fractures induced around the gallery wall during excavation. In this experiment, we developed a low-viscosity resin mixed with a fluorescent substance and injected it to the borehole drilled to be approximately 1 m in length. We then overcored around the injection borehole. The observation on the cut surface of the overcore under ultraviolet light revealed that the fractures were distributed within 0.8 m from the gallery wall. The fractures were interconnected with one another, particularly within 0.25 m from the niche wall. Furthermore, the fractures with a large aperture (ca. ~1.0 mm) were developed in that region. These observation results will provide fundamental information for understanding the fracturing process in the EDZ. 1. Introduction In the excavation of a repository for the high-level radioactive waste (HLW) disposal, fractures are induced around the gallery wall because of the resultant stress redistribution. This fracture zone is called the excavation damaged zone (EDZ) (Tsang et al. 2005). The hydraulic conductivity in the EDZ can increase and then lead to the migration pathway of the radionuclides from the disposal facilities (Japan Nuclear Cycle Development Institute, 2000). Therefore, it is important to understand the fracture characteristics causing the enhancement of the hydraulic conductivity in the EDZ for the performance of the comprehensive HLW disposal risk assessment. Many papers have reported the results of in-situ surveys and numerical analyses to study the hydro-mechanical behavior of the EDZ in various underground research laboratories (URLs) (e.g., Nuclear Waste Management Organization, 2011). The visualization of fractures in the EDZ is one of the best methods of investigating the fracture characteristics. For example, in the Mont Terri rock laboratory in Switzerland and Meuse/Haute-Marne URL in France, some researchers visualized the fracture network in the EDZ through a resin injection experiment and studied the results as supporting data to make a conceptual model of EDZ fractures induced around the gallery (Armand et al. 2007; 2014; Bossart et al. 2002; 2004; Kupferschmied et al. 2015).