Microseismic events (MSE) in underground mines are the result of stress perturbations and rock fr... more Microseismic events (MSE) in underground mines are the result of stress perturbations and rock fractures due to mining excavations. In the last decades, the problem of mining-induced seismicity has become more and more important due to the increasing depth of underground mines. Indeed, in situ stresses on average increase with depth, resulting in seismic activity intensification, both in terms of events rate and radiated seismic energy. Understanding how and why MSE occur is, then, a fundamental purpose in order to control the rate of seismicity and guarantee mine infrastructures and mine workers safety. With the aim of better understanding interactions between stress modifications induced by mining and the generation of seismic activity, different factors need to be taken into account: geological structures and rock properties, initial state of stress and stress modifications, but also mining method, excavation geometry and blasting practice, are some of the principal aspects affecting seismic activity in mines. This interaction between natural and anthropogenic parameters makes the understanding of mining-induced seismicity more complex, not only because the seismic response to mining will be unique at each mine, but also because it requires multi-parameter approaches. In this work we present data collected in the metal mine of Garpenberg (Sweden) exploited by the mining company Boliden, where a monitoring network was installed by INERIS between 1108 and 1257 meters below ground surface. The network consists in both one-component and three-component geophones for MSE recording, together with two geotechnical cells for local stress field changes monitoring. A comparative analysis of seismic and geotechnical data, together with information about mine production will be presented, in order to determine correlations between blasting procedures, MSE occurrences and local stress field modifications. It will be shown how mine blasts play an important role in seismic activity triggering, even if the rock mass response to mining appears to be very variable across space and time. Differences in rock mass behavior will be explained by considering local geology characteristics and stress redistribution in the monitored area. Indeed, increases in seismicity rate will be justified by the fact that some mine blasts have an effect on remote overstressed areas. This effect is intensified by the presence of weak geological zones which produce a heterogeneous distribution of the initial stress field. Seismic source parameters analysis will allow understanding differences in ruptures dynamics and source region characteristics between areas of the mine dominated by distinct geological properties. Finally, first results of numerical modeling will be presented and compared with the integrated analysis of geotechnical and geophysical data, with the aim of giving first insights on seismic risk prevention at Garpenberg mine and, more generally, in deep underground mines prone to rockbursts.
3rd International Symposium on Mine Safety Science and Engineering, Nov 28, 2016
This paper deals with the development of a non-linear constitutive model of rock mass and its ver... more This paper deals with the development of a non-linear constitutive model of rock mass and its verification to predict a damaged zone. Simulations of triaxial compressions provide a verification of the implementation with a good agreement between predictions and theoretical values of peak and residual strengths as well as the transition between brittle failure and ductile response. The applicability of the model to predict potential failure around stopes of a deep polymetallic ore mine is checked. The present study highlights the interest to consider more realistic rheology of hard rock masses compared with the elastic perfectly plastic models of underground deep mines.
Heib-Institut national de l'environnement industriel et des risques (Ineris), France Jan Burda-Vý... more Heib-Institut national de l'environnement industriel et des risques (Ineris), France Jan Burda-Výzkumný ústav pro hnědé uhlí (VUHU), Czech Republic
At the Meuse/Haute Marne Underground Research Laboratory, Andra has developed a technical and sci... more At the Meuse/Haute Marne Underground Research Laboratory, Andra has developed a technical and scientific program to test the feasibility of excavation of disposal cells for nuclear waste in a 500 m deep clay formation. Five micro-tunnels, 20 m long and 74 cm diameter will be excavated using a specially designed guided auger drilling machine. Different kinds of measurements and instrumentations will be carried out before, during and after excavation, to evaluate the performance of the excavation method, and to study the hydro-mechanical behavior of the host rock in response to the excavation. 3D numerical modeling has been performed for the prediction of hydro-mechanical and visco-plastic behavior and in the view of assisting the choice of measurements and instrumentations location.
-Dans le cadre de l'expérimentation "alvéoles HA" au laboratoire souterrain de recherche de Bure ... more -Dans le cadre de l'expérimentation "alvéoles HA" au laboratoire souterrain de recherche de Bure (Andra), des modélisations mécaniques couplées (comportement différé ou hydraulique) ont été réalisées pour prédire le comportement attendu des argilites à l'excavation d'une alvéole (contraintes, déplacements, EDZ). Elles sont ensuite comparées avec les mesures in situ (déplacements et pression interstitielle). ABSTRACT-For the "HA cells" experimentation in the URL of Bure (Andra), coupled mechanical modelings (creep or hydraulic behavior) were carried out to predict the expected behavior of argillites during excavation of a disposal cell (stresses, displacements, EDZ). These predictions are then compared to in situ measurements (displacement and pore pressure).
-Dans le cadre de l'expérimentation "alvéoles HA" au laboratoire souterrain de recherche de Bure ... more -Dans le cadre de l'expérimentation "alvéoles HA" au laboratoire souterrain de recherche de Bure (Andra), des modélisations mécaniques couplées (comportement différé ou hydraulique) ont été réalisées pour prédire le comportement attendu des argilites à l'excavation d'une alvéole (contraintes, déplacements, EDZ). Elles sont ensuite comparées avec les mesures in situ (déplacements et pression interstitielle). ABSTRACT-For the "HA cells" experimentation in the URL of Bure (Andra), coupled mechanical modelings (creep or hydraulic behavior) were carried out to predict the expected behavior of argillites during excavation of a disposal cell (stresses, displacements, EDZ). These predictions are then compared to in situ measurements (displacement and pore pressure).
This paper develops the studies carried out after the fatal accident occurred during the mining o... more This paper develops the studies carried out after the fatal accident occurred during the mining of Frieda5-1250 panel at Merlebach mine section of HBL (East France). On the 21 June 2001, a violent rockburst (local magnitude of 3.6) has affected the panel 1250 of Frieda5 coal seam. An investigation program was carried out to determine the causes of this accident and to understand the induced phenomenon. The program include: seismic investigations, geological and geotechnical analysis and numerical modeling. The objective is to determine eventually the presence of particular geological structures and there role in the initiation of the accident. After the accident, the HBL intended to mine the Seam 6. In order to monitor the behavior of the ground during the mining of the Seam 6, a geotechnical program comprising a complete study of the natural conditions and a seismic analysis was carried out. The environment of the panel is marked by the presence certain number of faults. Stress disturbed by the exploitation of the old panels and the presence of faults are likely to modify the equilibrium of strata before the exploitation and can induced seismicity. To study their influence, the INERIS carried out a numerical modeling in the scale of mine area (SUIT3D and FAULT3D), for the determination of the stress zone induced by old and new panels.
International Journal of Rock Mechanics and Mining Sciences, Jun 1, 2018
This paper deals with the development of a non-linear constitutive model of a rock mass and its a... more This paper deals with the development of a non-linear constitutive model of a rock mass and its application to predict the extension of the excavation damaged zone (EDZ) around openings. A comparison of the model results with the simulations of triaxial compression tests shows a good agreement between predictions and theoretical values of peak and residual strengths as well as a good reproduction of the transition between brittle failure and ductile response. The relevance of the proposed model to evaluate the potential failure around stopes of the Garpenberg mine was examined. The comparison of the results proved satisfactory and highlighted the interest of considering a more realistic mechanical behavior of hard rock masses in rock engineering compared with the elastic perfectly plastic models generally used in numerical modeling of underground deep mines. Finally, a 3D simulation of the complete mine geometry was carried out in order to model the first phases of stope mining operations. The predicted stresses were compared with the continuous measurements of induced in situ stresses recorded by stress cells at different points around the stope. The predictions of the proposed constitutive model provided a much better agreement with stress measurements than those obtained with elastic perfectly plastic models.
Bulletin of Engineering Geology and the Environment, Jun 23, 2022
Almost all post exploitation open pit mines in the world are shaped as a final water reservoir. O... more Almost all post exploitation open pit mines in the world are shaped as a final water reservoir. One of the main hazards is the slope stability of lake banks. To develop a reliability methodology for assessing the long-term stability of flooded open-pit lake, a back analysis was conducted using 2D and 3D large-scale numerical models of Lake Most, which is one of the largest mining lakes in Europe (Czech Republic). The large-scale numerical model was built, based on the site observations, large scale LiDAR data, in situ characterisation tests and statistical analysis of geotechnical data, on DTMs defining the complex geology of the site and on numerous piezometric levels to build the water table. Local and global safety factor (SF) were calculated using the strength reduction method. The results highlighted the reliability of the methodology to combine the geometric model with the geological model to create a large-scale numerical model, to identify local and potentially instable zones and to highlight the role of a weak contact layer. The calculation of 3D SF has shown a very good correlation between the lowest SF and the ground movement observations noted by the Czech authorities.
The number of abandoned mines is continuously increasing in the world. The sustainable exploitati... more The number of abandoned mines is continuously increasing in the world. The sustainable exploitation of these abandoned mines is a top priority globally. Pit lakes created in abandoned mining sites provide benefits and present risks for the mining region. This paper presents a methodology to assess the mining and natural hazards related to pit lakes. The proposed methodology framework is based on well-established and internationally accepted risk management standards and allows the assessment of the long-term stability of pit lakes. Potential ground movements, water pollution, fire hazards are presented, and their impact evaluated based on feedback and international experience. The methodology was applied for 13 European pit lakes created in former European coal and lignite mines. A risk assessment of the Most lake was carried out, using qualitative and a weighted probabilistic approach that considers the overall and the individual effect of identified mining and natural hazards. Results showed that the main potential hazards are the ground movements, slope stability, and flooding.
With the aim of understanding the nature of mining-induced seismicity, microseismic activity in t... more With the aim of understanding the nature of mining-induced seismicity, microseismic activity in the deep metal mine of Garpenberg (Sweden) has been recorded during 2 years of excavations. The studied area of the mine is operated using sublevel stoping method with backfilling, between depths of around 1000 and 1300 meters. Spatiotemporal analysis of microseismic activity is presented and correlated with the occurrence of mining blasts. A clear dependence is observed between blasts and seismic sequences, even if the rock mass response to mining appears to be very variable across space and time. Two main clusters are observed: one located in the major production area (Central Cluster), while the second (Right Cluster) is located at some distance from the excavations, in a zone characterized by a heterogeneous distribution of weak materials and stiff rock masses. By analyzing seismic source parameters, we demonstrate that the two clusters are characterized by different dynamics. In addition, we show how Right Cluster events are mainly controlled by geological heterogeneities, which impose high stress concentrations in the stiff rock masses surrounding weak lenses. High apparent stresses and corner frequencies associated with the Right Cluster events agree with our proposed model. This suggests elevated stresses in the seismic source region and small source dimensions; indeed, fractures cannot propagate along great distances due to the presence of weak lenses interbedded with the breaking stiff rock mass.
In order to demonstrate the feasibility of radioactive waste repository in deep geological format... more In order to demonstrate the feasibility of radioactive waste repository in deep geological formation, an underground research laboratory is being constructed by Andra (French national radioactive waste management agency) in eastern France, in a Callovo-Oxfordian claystone. 15 boreholes were drilled from a drift at-447 m to install sensors around the shaft (6 m diameter) at depth-460 m to-474 m in order to record the hydromechanical behaviour of the claystone during a shaft sinking (drill and blast method). This paper is devoted to the analysis of the mechanical and hydromechanical behaviour observed during the shaft sinking. Analytical approach used herein allows to realistically evaluate the undrained response of the shaft neighboring with agreement with the in situ measurements. For the transient phase, prediction is qualitatively in accordance with measurement. In addition, deformation and displacement measurements are successfully compared to a simple 3D elastic calculation performed with the real face advancing. This emphasizes the quality of the data set which would be compared in the Modex-Rep European project with complex numerical modelling (poro-elasto-plasic-damage models, creep behaviour, …). RÉSUMÉ En France, l'Andra (Agence Nationale de gestion des déchets radioactifs) est en charge des études pour la faisabilité d'un stockage de déchet radioactif haute activité à vie longue, dans une formation géologique profonde comme des argiles. Pour cela, l'Andra a construit le laboratoire de recherche souterrain de Meuse Haute Marne dans le Nord-Est de la France (à 300 km environs de Paris) dans une formation d'argilite du Callovo-Oxfordien qui se trouve entre 420 m et 550 m au niveau du puits principal. La première expérimentation géomécanique réalisée dans le laboratoire est un « mine by test » autour du puits principal (diamètre 6 m). A partir d'une galerie se trouvant à-445 m, 15 forages ont été réalisés pour installer des capteurs et mesurer le comportement hydromécanique de l'argilite entre-460 et-470 m lors du creusement du puits principal. Les évolutions des mesures in situ sont présentées et comparées avec la solution analytique poro-élastique du creusement d'un puits infini. Les mesures de déplacement sont comparées avec les résultats d'un calcul élastique en 3D. Ces analyses simples montrent la cohérence et la qualité des différentes mesures in situ qui serviront de données de référence dans le projet Européen ModexRep, où le creusement du puits est simulé avec des modèles 3D complexes (poro-elasto-endo-plasticité, fluage, ….). 1.
-Dans le cadre de l'expérimentation "alvéoles HA" au laboratoire souterrain de recherche de Bure ... more -Dans le cadre de l'expérimentation "alvéoles HA" au laboratoire souterrain de recherche de Bure (Andra), des modélisations mécaniques couplées (comportement différé ou hydraulique) ont été réalisées pour prédire le comportement attendu des argilites à l'excavation d'une alvéole (contraintes, déplacements, EDZ). Elles sont ensuite comparées avec les mesures in situ (déplacements et pression interstitielle). ABSTRACT-For the "HA cells" experimentation in the URL of Bure (Andra), coupled mechanical modelings (creep or hydraulic behavior) were carried out to predict the expected behavior of argillites during excavation of a disposal cell (stresses, displacements, EDZ). These predictions are then compared to in situ measurements (displacement and pore pressure).
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The excavation of a deep underground structure induces a stress field redistribution that creates... more The excavation of a deep underground structure induces a stress field redistribution that creates an Excavation Damaged Zone (EDZ). Study of EDZ physical properties is of prime importance in the framework of nuclear waste geological storage, where EDZ constitutes a preferential pathway for storage materials towards the biosphere. Use of ultrasonic wave propagation inside the rock media is of great help as a near field non-intrusive technique for this. The significant research activity in the laboratory offers a large number of boreholes. These boreholes form linear excavations with a perfectly round section. It is for this reason that a specific probe and inversion method have been developed in order to reconstruct the image of the velocity field all around the environment of the boreholes. In order to recover all data needed with high accuracy and minimum effort, the probe is fully monitored for automatic data acquisition. This numerical inversion method has been preliminarily applied to a multi layer test bed in order to validate and optimise the experimental and numerical procedures. Based on those results, an in situ experiment has been performed in the Meuse/Haute-Marne Underground Research Laboratory (URL) in France for the safety assessment of nuclear waste storage in the Callovo-Oxfordian argillaceous layer.
Microseismic events (MSE) in underground mines are the result of stress perturbations and rock fr... more Microseismic events (MSE) in underground mines are the result of stress perturbations and rock fractures due to mining excavations. In the last decades, the problem of mining-induced seismicity has become more and more important due to the increasing depth of underground mines. Indeed, in situ stresses on average increase with depth, resulting in seismic activity intensification, both in terms of events rate and radiated seismic energy. Understanding how and why MSE occur is, then, a fundamental purpose in order to control the rate of seismicity and guarantee mine infrastructures and mine workers safety. With the aim of better understanding interactions between stress modifications induced by mining and the generation of seismic activity, different factors need to be taken into account: geological structures and rock properties, initial state of stress and stress modifications, but also mining method, excavation geometry and blasting practice, are some of the principal aspects affecting seismic activity in mines. This interaction between natural and anthropogenic parameters makes the understanding of mining-induced seismicity more complex, not only because the seismic response to mining will be unique at each mine, but also because it requires multi-parameter approaches. In this work we present data collected in the metal mine of Garpenberg (Sweden) exploited by the mining company Boliden, where a monitoring network was installed by INERIS between 1108 and 1257 meters below ground surface. The network consists in both one-component and three-component geophones for MSE recording, together with two geotechnical cells for local stress field changes monitoring. A comparative analysis of seismic and geotechnical data, together with information about mine production will be presented, in order to determine correlations between blasting procedures, MSE occurrences and local stress field modifications. It will be shown how mine blasts play an important role in seismic activity triggering, even if the rock mass response to mining appears to be very variable across space and time. Differences in rock mass behavior will be explained by considering local geology characteristics and stress redistribution in the monitored area. Indeed, increases in seismicity rate will be justified by the fact that some mine blasts have an effect on remote overstressed areas. This effect is intensified by the presence of weak geological zones which produce a heterogeneous distribution of the initial stress field. Seismic source parameters analysis will allow understanding differences in ruptures dynamics and source region characteristics between areas of the mine dominated by distinct geological properties. Finally, first results of numerical modeling will be presented and compared with the integrated analysis of geotechnical and geophysical data, with the aim of giving first insights on seismic risk prevention at Garpenberg mine and, more generally, in deep underground mines prone to rockbursts.
3rd International Symposium on Mine Safety Science and Engineering, Nov 28, 2016
This paper deals with the development of a non-linear constitutive model of rock mass and its ver... more This paper deals with the development of a non-linear constitutive model of rock mass and its verification to predict a damaged zone. Simulations of triaxial compressions provide a verification of the implementation with a good agreement between predictions and theoretical values of peak and residual strengths as well as the transition between brittle failure and ductile response. The applicability of the model to predict potential failure around stopes of a deep polymetallic ore mine is checked. The present study highlights the interest to consider more realistic rheology of hard rock masses compared with the elastic perfectly plastic models of underground deep mines.
Heib-Institut national de l'environnement industriel et des risques (Ineris), France Jan Burda-Vý... more Heib-Institut national de l'environnement industriel et des risques (Ineris), France Jan Burda-Výzkumný ústav pro hnědé uhlí (VUHU), Czech Republic
At the Meuse/Haute Marne Underground Research Laboratory, Andra has developed a technical and sci... more At the Meuse/Haute Marne Underground Research Laboratory, Andra has developed a technical and scientific program to test the feasibility of excavation of disposal cells for nuclear waste in a 500 m deep clay formation. Five micro-tunnels, 20 m long and 74 cm diameter will be excavated using a specially designed guided auger drilling machine. Different kinds of measurements and instrumentations will be carried out before, during and after excavation, to evaluate the performance of the excavation method, and to study the hydro-mechanical behavior of the host rock in response to the excavation. 3D numerical modeling has been performed for the prediction of hydro-mechanical and visco-plastic behavior and in the view of assisting the choice of measurements and instrumentations location.
-Dans le cadre de l'expérimentation "alvéoles HA" au laboratoire souterrain de recherche de Bure ... more -Dans le cadre de l'expérimentation "alvéoles HA" au laboratoire souterrain de recherche de Bure (Andra), des modélisations mécaniques couplées (comportement différé ou hydraulique) ont été réalisées pour prédire le comportement attendu des argilites à l'excavation d'une alvéole (contraintes, déplacements, EDZ). Elles sont ensuite comparées avec les mesures in situ (déplacements et pression interstitielle). ABSTRACT-For the "HA cells" experimentation in the URL of Bure (Andra), coupled mechanical modelings (creep or hydraulic behavior) were carried out to predict the expected behavior of argillites during excavation of a disposal cell (stresses, displacements, EDZ). These predictions are then compared to in situ measurements (displacement and pore pressure).
-Dans le cadre de l'expérimentation "alvéoles HA" au laboratoire souterrain de recherche de Bure ... more -Dans le cadre de l'expérimentation "alvéoles HA" au laboratoire souterrain de recherche de Bure (Andra), des modélisations mécaniques couplées (comportement différé ou hydraulique) ont été réalisées pour prédire le comportement attendu des argilites à l'excavation d'une alvéole (contraintes, déplacements, EDZ). Elles sont ensuite comparées avec les mesures in situ (déplacements et pression interstitielle). ABSTRACT-For the "HA cells" experimentation in the URL of Bure (Andra), coupled mechanical modelings (creep or hydraulic behavior) were carried out to predict the expected behavior of argillites during excavation of a disposal cell (stresses, displacements, EDZ). These predictions are then compared to in situ measurements (displacement and pore pressure).
This paper develops the studies carried out after the fatal accident occurred during the mining o... more This paper develops the studies carried out after the fatal accident occurred during the mining of Frieda5-1250 panel at Merlebach mine section of HBL (East France). On the 21 June 2001, a violent rockburst (local magnitude of 3.6) has affected the panel 1250 of Frieda5 coal seam. An investigation program was carried out to determine the causes of this accident and to understand the induced phenomenon. The program include: seismic investigations, geological and geotechnical analysis and numerical modeling. The objective is to determine eventually the presence of particular geological structures and there role in the initiation of the accident. After the accident, the HBL intended to mine the Seam 6. In order to monitor the behavior of the ground during the mining of the Seam 6, a geotechnical program comprising a complete study of the natural conditions and a seismic analysis was carried out. The environment of the panel is marked by the presence certain number of faults. Stress disturbed by the exploitation of the old panels and the presence of faults are likely to modify the equilibrium of strata before the exploitation and can induced seismicity. To study their influence, the INERIS carried out a numerical modeling in the scale of mine area (SUIT3D and FAULT3D), for the determination of the stress zone induced by old and new panels.
International Journal of Rock Mechanics and Mining Sciences, Jun 1, 2018
This paper deals with the development of a non-linear constitutive model of a rock mass and its a... more This paper deals with the development of a non-linear constitutive model of a rock mass and its application to predict the extension of the excavation damaged zone (EDZ) around openings. A comparison of the model results with the simulations of triaxial compression tests shows a good agreement between predictions and theoretical values of peak and residual strengths as well as a good reproduction of the transition between brittle failure and ductile response. The relevance of the proposed model to evaluate the potential failure around stopes of the Garpenberg mine was examined. The comparison of the results proved satisfactory and highlighted the interest of considering a more realistic mechanical behavior of hard rock masses in rock engineering compared with the elastic perfectly plastic models generally used in numerical modeling of underground deep mines. Finally, a 3D simulation of the complete mine geometry was carried out in order to model the first phases of stope mining operations. The predicted stresses were compared with the continuous measurements of induced in situ stresses recorded by stress cells at different points around the stope. The predictions of the proposed constitutive model provided a much better agreement with stress measurements than those obtained with elastic perfectly plastic models.
Bulletin of Engineering Geology and the Environment, Jun 23, 2022
Almost all post exploitation open pit mines in the world are shaped as a final water reservoir. O... more Almost all post exploitation open pit mines in the world are shaped as a final water reservoir. One of the main hazards is the slope stability of lake banks. To develop a reliability methodology for assessing the long-term stability of flooded open-pit lake, a back analysis was conducted using 2D and 3D large-scale numerical models of Lake Most, which is one of the largest mining lakes in Europe (Czech Republic). The large-scale numerical model was built, based on the site observations, large scale LiDAR data, in situ characterisation tests and statistical analysis of geotechnical data, on DTMs defining the complex geology of the site and on numerous piezometric levels to build the water table. Local and global safety factor (SF) were calculated using the strength reduction method. The results highlighted the reliability of the methodology to combine the geometric model with the geological model to create a large-scale numerical model, to identify local and potentially instable zones and to highlight the role of a weak contact layer. The calculation of 3D SF has shown a very good correlation between the lowest SF and the ground movement observations noted by the Czech authorities.
The number of abandoned mines is continuously increasing in the world. The sustainable exploitati... more The number of abandoned mines is continuously increasing in the world. The sustainable exploitation of these abandoned mines is a top priority globally. Pit lakes created in abandoned mining sites provide benefits and present risks for the mining region. This paper presents a methodology to assess the mining and natural hazards related to pit lakes. The proposed methodology framework is based on well-established and internationally accepted risk management standards and allows the assessment of the long-term stability of pit lakes. Potential ground movements, water pollution, fire hazards are presented, and their impact evaluated based on feedback and international experience. The methodology was applied for 13 European pit lakes created in former European coal and lignite mines. A risk assessment of the Most lake was carried out, using qualitative and a weighted probabilistic approach that considers the overall and the individual effect of identified mining and natural hazards. Results showed that the main potential hazards are the ground movements, slope stability, and flooding.
With the aim of understanding the nature of mining-induced seismicity, microseismic activity in t... more With the aim of understanding the nature of mining-induced seismicity, microseismic activity in the deep metal mine of Garpenberg (Sweden) has been recorded during 2 years of excavations. The studied area of the mine is operated using sublevel stoping method with backfilling, between depths of around 1000 and 1300 meters. Spatiotemporal analysis of microseismic activity is presented and correlated with the occurrence of mining blasts. A clear dependence is observed between blasts and seismic sequences, even if the rock mass response to mining appears to be very variable across space and time. Two main clusters are observed: one located in the major production area (Central Cluster), while the second (Right Cluster) is located at some distance from the excavations, in a zone characterized by a heterogeneous distribution of weak materials and stiff rock masses. By analyzing seismic source parameters, we demonstrate that the two clusters are characterized by different dynamics. In addition, we show how Right Cluster events are mainly controlled by geological heterogeneities, which impose high stress concentrations in the stiff rock masses surrounding weak lenses. High apparent stresses and corner frequencies associated with the Right Cluster events agree with our proposed model. This suggests elevated stresses in the seismic source region and small source dimensions; indeed, fractures cannot propagate along great distances due to the presence of weak lenses interbedded with the breaking stiff rock mass.
In order to demonstrate the feasibility of radioactive waste repository in deep geological format... more In order to demonstrate the feasibility of radioactive waste repository in deep geological formation, an underground research laboratory is being constructed by Andra (French national radioactive waste management agency) in eastern France, in a Callovo-Oxfordian claystone. 15 boreholes were drilled from a drift at-447 m to install sensors around the shaft (6 m diameter) at depth-460 m to-474 m in order to record the hydromechanical behaviour of the claystone during a shaft sinking (drill and blast method). This paper is devoted to the analysis of the mechanical and hydromechanical behaviour observed during the shaft sinking. Analytical approach used herein allows to realistically evaluate the undrained response of the shaft neighboring with agreement with the in situ measurements. For the transient phase, prediction is qualitatively in accordance with measurement. In addition, deformation and displacement measurements are successfully compared to a simple 3D elastic calculation performed with the real face advancing. This emphasizes the quality of the data set which would be compared in the Modex-Rep European project with complex numerical modelling (poro-elasto-plasic-damage models, creep behaviour, …). RÉSUMÉ En France, l'Andra (Agence Nationale de gestion des déchets radioactifs) est en charge des études pour la faisabilité d'un stockage de déchet radioactif haute activité à vie longue, dans une formation géologique profonde comme des argiles. Pour cela, l'Andra a construit le laboratoire de recherche souterrain de Meuse Haute Marne dans le Nord-Est de la France (à 300 km environs de Paris) dans une formation d'argilite du Callovo-Oxfordien qui se trouve entre 420 m et 550 m au niveau du puits principal. La première expérimentation géomécanique réalisée dans le laboratoire est un « mine by test » autour du puits principal (diamètre 6 m). A partir d'une galerie se trouvant à-445 m, 15 forages ont été réalisés pour installer des capteurs et mesurer le comportement hydromécanique de l'argilite entre-460 et-470 m lors du creusement du puits principal. Les évolutions des mesures in situ sont présentées et comparées avec la solution analytique poro-élastique du creusement d'un puits infini. Les mesures de déplacement sont comparées avec les résultats d'un calcul élastique en 3D. Ces analyses simples montrent la cohérence et la qualité des différentes mesures in situ qui serviront de données de référence dans le projet Européen ModexRep, où le creusement du puits est simulé avec des modèles 3D complexes (poro-elasto-endo-plasticité, fluage, ….). 1.
-Dans le cadre de l'expérimentation "alvéoles HA" au laboratoire souterrain de recherche de Bure ... more -Dans le cadre de l'expérimentation "alvéoles HA" au laboratoire souterrain de recherche de Bure (Andra), des modélisations mécaniques couplées (comportement différé ou hydraulique) ont été réalisées pour prédire le comportement attendu des argilites à l'excavation d'une alvéole (contraintes, déplacements, EDZ). Elles sont ensuite comparées avec les mesures in situ (déplacements et pression interstitielle). ABSTRACT-For the "HA cells" experimentation in the URL of Bure (Andra), coupled mechanical modelings (creep or hydraulic behavior) were carried out to predict the expected behavior of argillites during excavation of a disposal cell (stresses, displacements, EDZ). These predictions are then compared to in situ measurements (displacement and pore pressure).
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The excavation of a deep underground structure induces a stress field redistribution that creates... more The excavation of a deep underground structure induces a stress field redistribution that creates an Excavation Damaged Zone (EDZ). Study of EDZ physical properties is of prime importance in the framework of nuclear waste geological storage, where EDZ constitutes a preferential pathway for storage materials towards the biosphere. Use of ultrasonic wave propagation inside the rock media is of great help as a near field non-intrusive technique for this. The significant research activity in the laboratory offers a large number of boreholes. These boreholes form linear excavations with a perfectly round section. It is for this reason that a specific probe and inversion method have been developed in order to reconstruct the image of the velocity field all around the environment of the boreholes. In order to recover all data needed with high accuracy and minimum effort, the probe is fully monitored for automatic data acquisition. This numerical inversion method has been preliminarily applied to a multi layer test bed in order to validate and optimise the experimental and numerical procedures. Based on those results, an in situ experiment has been performed in the Meuse/Haute-Marne Underground Research Laboratory (URL) in France for the safety assessment of nuclear waste storage in the Callovo-Oxfordian argillaceous layer.
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