This thesis presents new developments of the IntegratedStress Determination Method (ISDM) with application to the AspoHard Rock Laboratory (HRL), Oskarshamn, Sweden. The newdevelopments involve a 12-parameter representation of theregional stress field in the rock mass. The method isapplicable to data from hydraulic fracturing, hydraulic testson pre-existing fractures (HTPF), and overcoring data fromCSIR- and CSIRO-type of devices. When hydraulic fracturing/HTPFdata are combined with overcoring data, the former may be usedto constrain the elastic parameters, i.e. the problem involves14 model parameters. The Swedish Nuclear Fuel and Waste Management Co. (SKB),have conducted a vast amount of rock stress measurements at theAspo Hard Rock Laboratory (HRL) since the late 1980s. However,despite the large number of stress measurement data collectedin this limited rock volume, variability in the stress fieldexists. Not only does the result vary depending on measuringtechnique, e.g. overcoring data indicated larger stressmagnitudes compared to hydraulic fracturing data; the resultsare also affected by existing discontinuities, indicated bynon-linear stress magnitudes and orientations versus depth. The objectives for this study are therefore threefold: (1)find explanations to the observed differences between existinghydraulic and overcoring stress data at the Aspo HRL; (2)explain the non-linear stress distribution indicated byexisting stress data; and (3) apply the ISDM, including the newdevelopments, based on the results obtained in step 1 and2. To evaluate the observed differences between existinghydraulic and overcoring stress data, a detailedre-interpretation was conducted. Several measurement-relateduncertainties were identified and corrected for when possible,which effectively reduced the discrepancies between thehydraulic and overcoring measuring results. Modeling studies managed by SKB have shown that theredistribution of the stresses at Aspo HRL to a large extentcan be correlated to the NE-2 Fracture Zone, which divides therock stress data into two stress domains. The effect of thiszone was confirmed in this study, and the re-analyzed datasuggest an orientation of σ1equal to 124oN±13ofor the NW domain and 139oN±18ofor the SE domain. Later, the application of theISDM further verified the influence of the NE-2 Fracture Zoneon the regional stress field. The results in the vicinity ofthe NE-2 Fracture Zone indicate that σ1is perpendicular to the zone, whereas the σ2and σ3coincide with the plane defined by the zone(strike 21oN, dip 77otowards SE). However, the principal stressmagnitudes seem less influenced by the zone. The amount of data located outside the zone of influencefrom the NE-2 Fracture Zone is limited, and the regional stresstensor is hence difficult to define. Most likely, theorientation of the regional σ1is trending about 140oN.

<p>This thesis presents new developments of the IntegratedStress Determination Method (ISDM) with application to the AspoHard Rock Laboratory (HRL), Oskarshamn, Sweden. The newdevelopments involve a 12-parameter representation of theregional stress field in the rock mass. The method isapplicable to data from hydraulic fracturing, hydraulic testson pre-existing fractures (HTPF), and overcoring data fromCSIR- and CSIRO-type of devices. When hydraulic fracturing/HTPFdata are combined with overcoring data, the former may be usedto constrain the elastic parameters, i.e. the problem involves14 model parameters.</p><p>The Swedish Nuclear Fuel and Waste Management Co. (SKB),have conducted a vast amount of rock stress measurements at theAspo Hard Rock Laboratory (HRL) since the late 1980s. However,despite the large number of stress measurement data collectedin this limited rock volume, variability in the stress fieldexists. Not only does the result vary depending on measuringtechnique, e.g. overcoring data indicated larger stressmagnitudes compared to hydraulic fracturing data; the resultsare also affected by existing discontinuities, indicated bynon-linear stress magnitudes and orientations versus depth.</p><p>The objectives for this study are therefore threefold: (1)find explanations to the observed differences between existinghydraulic and overcoring stress data at the Aspo HRL; (2)explain the non-linear stress distribution indicated byexisting stress data; and (3) apply the ISDM, including the newdevelopments, based on the results obtained in step 1 and2.</p><p>To evaluate the observed differences between existinghydraulic and overcoring stress data, a detailedre-interpretation was conducted. Several measurement-relateduncertainties were identified and corrected for when possible,which effectively reduced the discrepancies between thehydraulic and overcoring measuring results.</p><p>Modeling studies managed by SKB have shown that theredistribution of the stresses at Aspo HRL to a large extentcan be correlated to the NE-2 Fracture Zone, which divides therock stress data into two stress domains. The effect of thiszone was confirmed in this study, and the re-analyzed datasuggest an orientation of σ₁equal to 124^oN±13^ofor the NW domain and 139^oN±18^ofor the SE domain. Later, the application of theISDM further verified the influence of the NE-2 Fracture Zoneon the regional stress field. The results in the vicinity ofthe NE-2 Fracture Zone indicate that σ₁is perpendicular to the zone, whereas the σ₂and σ₃coincide with the plane defined by the zone(strike 21^oN, dip 77^otowards SE). However, the principal stressmagnitudes seem less influenced by the zone.</p><p>The amount of data located outside the zone of influencefrom the NE-2 Fracture Zone is limited, and the regional stresstensor is hence difficult to define. Most likely, theorientation of the regional σ₁is trending about 140^oN.</p>

No description available.

Dans le cadre de la problématique de l'enfouissement des déchets nucléaires, la barrière géologique constitue la dernière zone de transfert des radio-éléments. Cette barrière pouvant être fracturée des recherches sont menées pour faire progresser la modélisation des transferts en milieu fracturé. La complexité du milieu, les contrastes existant entre les différentes zones et les incertitudes liées aux propriétés physiques rendent cette tâche complexe. De plus, après fermeture du site, les écoulements lents dans le milieu favorisent des phénomènes diffusifs dans la roche qui contribuent à augmenter le temps de transit des radio-éléments. Dans ce contexte, une approche Smeared Fractures a été développée pour un schéma en Eléments Finis Mixtes Hybrides et implémentée dans le code Cast3M. Cette approche permet une représentation explicite des fractures principales alors que la fracturation de plus petite échelle est homogénéisée. L'utilisation d'un maillage régulier permet, en outre, d'éviter un maillage explicite coûteux. La présence des fractures est prise en compte par un champ hétérogène de propriétés. Ces propriétés sont affectées de manière à respecter les critères de conservation des flux (hydraulique et massique) à l'échelle de la fracture. Pour l'écoulement, l'approche Smeared Fractures présente des performances comparables à celles obtenues avec des approches discrètes tandis que le caractère 3D de la géométrie des blocs matriciels est respecté lors de la résolution du transport. Le choix des discrétisation spatiale et temporelle doit respecter des critères qui ont été établis. Néanmoins, à l'intérieur de ces limites, et suivant la précision désirée, l'approche permet de réduire les temps de calcul. Les résultats de validation et de qualification de l'approche appliquée à des géométries 2D et 3D, synthétiques et réalistes, sont présentés pour différents jeux de paramètres physiques. Des applications de l'approche au site d'Äspö (Suède) clôturent ce travail.

No description available.