NorSand-aUL : une loi de comportement améliorée pour la modélisation des sables sous sollicitations statiques et cycliques

Cette thèse de doctorat porte sur la modélisation numérique du comportement des sables à l'aide de la loi de comportement NorSand-aUL. Cette loi, développée dans le cadre de ce projet de recherche, est une évolution du modèle NorSand spécifiquement adaptée à la modélisation du comportement des sables soumis à des sollicitations cycliques. La révision des performances de NorSand sous différents types de sollicitations (triaxial compression, cisaillement simple statique et cyclique, cisaillement à direction et ratio des contraintes principales contrôlés) a permis l'identification de certains points faibles du modèle, rendant ses modélisations du comportement des sables sous sollicitations cycliques insatisfaisantes. Afin de corriger ces lacunes, deux groupes de modifications ont été proposés. D'abord, la théorie de l'état critique anisotrope a été implémentée dans NorSand, afin d'y créer une dépendance vis-à-vis du type et de la direction des chargements. Cette modification a grandement amélioré les performances du modèle pour la modélisation du comportement encisaillement simple statique. La deuxième modification proposée s'est articulée autour de la formulation d'une nouvelle mécanique de génération de la plasticité lors du déchargement des sables. L'existence d'une deuxième surface de plasticité, nichée à l'intérieur de la surface de plasticité originale de NorSand, a été postulée. Les capacités de modélisation d'une version de NorSand incorporant cette nouvelle mécanique ont été confirmées grâce à la modélisation d'essais triaxiaux drainés et non drainés comprenant des phases de déchargement. Les deux modifications proposées au modèle NorSand au cours de ce projet de recherche ont finalement été agrégées pour mener à la formulation de NorSand-aUL. Ce nouveau modèle a été utilisé pour la modélisation d'essais de cisaillement simple cyclique effectués sur deux sables. Ces modélisations ont démontré les gains réalisés, particulièrement pour les essais effectués sur sable lâche, par rapport aux performances antérieurement obtenues à l'aide de la version originale de NorSand. Des axes de recherche future ont été proposés afin d'améliorer les performances de NorSand-aUL, notamment pour la modélisation du comportement des sables denses soumis à des sollicitations cycliques.This PhD thesis deals with the numerical modelling of sand behaviour using the NorSandaUL constitutive law. This law, developed as part of this research project, is an evolution ofthe NorSand model specifically adapted to the modelling of sand behaviour under cyclicloading. The review of NorSand's performance under various types of loading (triaxial compression, static and cyclic simple shear, fixed principal stress direction and fixed principal stress ratio) has allowed the identification of certain weak points in the model, making its behaviour modellings under cyclic loading unsatisfactory. In order to address these short comings, two groups of modifications were proposed. First, the anisotropic criticalstate theory was implemented in NorSand, in order to create a dependency on the type and direction of loading. This modification greatly improved the performance of the model for predicting static simple shear behavior. The second proposed modification focused on the formulation of a new mechanics for the generation of plasticity during unloading. The existence of a second yield surface, nested within the original NorSand yield surface, was postulated. The modelling capabilities of a version of NorSand incorporating this new mechanics were confirmed by satisfactory modelling results of drained and undrained triaxialtests which included unloading phases. The two modifications to NorSand proposed over the course this research project were eventually aggregated to lead to the formulation of NorSand-aUL. This new model was used to model cyclic simple shear tests for two sands. These modelling results demonstrated the gains made, particularly for tests conducted on loose sands, compared to the performance previously obtained using the original version of NorSand. Areas for future research were proposed to improve the performance of NorSandaUL, particularly in modelling the behaviour of dense sands under cyclic loading

Comportement du till de Romaine 3 soumis à des sollicitations cycliques

La résistance du till de la Romaine 3 a été étudiée sous sollicitations cycliques grâce à un nouvel appareil de cisaillement simple cyclique. Les essais ont été effectués à différentes teneurs en eau de compactage (côté sec et côté humide de l’optimum Proctor) et à différentes contraintes de cisaillement cyclique. Il a été démontré que les échantillons compactés du côté sec de l’optimum Proctor ont nécessité environ dix fois plus de cycles de cisaillement pour atteindre la rupture que les échantillons compactés du côté humide. Les essais effectués à faible ratio de cisaillement ont aussi nécessité l’application de dix fois plus de cycles de cisaillement que ceux effectués à ratio de cisaillement élevé avant d’atteindre la rupture. Le projet de recherche présenté s’inscrit dans le cadre de la chaire de recherche industrielle CRSNG – Hydro-Québec sur l’optimisation du cycle de vie des barrages en remblai.The resistance of Romaine 3 till was studied under cyclic loading using a new cyclic simple shear apparatus. The tests were carried out at different compaction water contents (dry and wet sides of Proctor optimum) and at different cyclic shear stress levels. It was found that ten times more cycles were needed for samples compacted on the dry side of optimum to reach failure than for samples compacted on the wet side of optimum. It was also found that the tests carried out at low cyclic stress ratio took ten times more cycles to reach failure then tests carried out at high cyclic stress ratios. The presented research project is part of the NSERC – Hydro-Québec Industrial Research Chair in life cycle optimisation for embankment dams

Copy-number variants and polygenic risk for intelligence confer risk for autism spectrum disorder irrespective of their effects on cognitive ability

IntroductionRare copy number variants (CNVs) and polygenic risk for intelligence (PRS-IQ) both confer susceptibility for autism spectrum disorder (ASD) but have opposing effects on cognitive ability. The field has struggled to disentangle the effects of these two classes of genomic variants on cognitive ability from their effects on ASD susceptibility, in part because previous studies did not include controls with cognitive measures. We aim to investigate the impact of these genomic variants on ASD risk while adjusting for their known effects on cognitive ability.MethodsIn a cohort of 8,426 subjects with ASD and 169,804 controls with cognitive assessments, we found that rare coding CNVs and PRS-IQ increased ASD risk, even after adjusting for their effects on cognitive ability.ResultsBottom decile PRS-IQ and CNVs both decreased cognitive ability but had opposing effects on ASD risk. Models combining both classes of variants showed that the effects of rare CNVs and PRS-IQ on ASD risk and cognitive ability were largely additive, further suggesting that susceptibility for ASD is conferred independently from its effects on cognitive ability. Despite imparting mostly additive effects on ASD risk, rare CNVs and PRS-IQ showed opposing effects on core and associated features and developmental history among subjects with ASD.DiscussionOur findings suggest that cognitive ability itself may not be the factor driving the underlying liability for ASD conferred by these two classes of genomic variants. In other words, ASD risk and cognitive ability may be two distinct manifestations of CNVs and PRS-IQ. This study also highlights the challenge of understanding how genetic risk for ASD maps onto its dimensional traits

National and Local Definitions of an Environmental Nuisance: Water Pollution and River Decontamination in Six Urban Areas of Quebec, 1945–1980

When it created the Water Purification Board in 1961, the Quebec government intended to proceed with a major reorganization of the municipal wastewater treatment and drinking water systems throughout the province. In the following decades, the Department of Municipal Affairs and Environment developed a series of programs and policies for the treatment of wastewater. If water pollution then appeared as a national problem and the subject of a consensual definition, neighbouring communities were facing specific problems that government policies tended to obscure. Our analysis of six municipalities (Drummondville, Sherbrooke, Saint-Hyacinthe, Granby, Trois-Rivières, and Shawinigan) located in three river basins (Saint-François, Yamaska, and Saint-Maurice), each with its own topography and hydrology, population, and industrial growth, and political and cultural history, reveals precisely how communities articulated their different understandings of pollution problems, as well as their distinct definitions of nuisance and means of coping with pollution. By identifying, at the local level, multiple representations of pollution phenomena and practices put forward to decontaminate water, we shed light on the difficulties surrounding the implementation of water treatment infrastructure in municipalities across Quebec between 1945 and 1980.À partir de 1961, avec la création de la Régie d’épuration des eaux, l’État québécois entreprend de procéder à une réorganisation majeure des systèmes de traitement des eaux usées et d’approvisionnement en eau potable dans les municipalités de la province. Au cours des décennies qui vont suivre, les ministères des Affaires municipales et de l’Environnement mettent au point une série de programmes et de politiques pour améliorer la qualité des eaux usées. Si l’enjeu de la pollution des eaux semble faire consensus à l’échelle provinciale et même, être l’objet d’une définition commune, il demeure que les communautés riveraines sont aux prises avec des problèmes particuliers que les politiques gouvernementales tendent à occulter. Notre analyse de six municipalités (Drummondville, Sherbrooke, Saint-Hyacinthe, Granby, Trois-Rivières et Shawinigan) sises sur les rives de trois rivières (Saint-François, Yamaska and Saint-Maurice), formant différents milieux au regard tant de la topographie et de l’hydrologie que de la croissance démographique et industrielle, révèle précisément que les modalités de prise en charge du phénomène de la pollution laissent transparaître des appréhensions spécifiques de la nuisance et des moyens de l’éradiquer. En identifiant, à l’échelle locale, les multiples représentations des phénomènes de pollution et les pratiques conséquemment mises de l’avant pour procéder à la décontamination de l’eau, nous jetons un éclairage sur les difficultés entourant l’implantation des infrastructures de traitement des eaux à travers le Québec entre 1945 et 1980

Optimizing Backrest Geometry to Minimize Interfacial Pressure Concentrations in the Mid-to-Lumbar Region During Leg Press Resistance Training

The leg press is a resistance training (RT) exercise common to both weight- and powerlifting, where spine-related injuries remain prevalent. Here, the elevated loading has the potential to result in increased pressure on vertebral bodies and introduce the risk of spinal injury. This study, therefore, investigates back interfacial pressure under leg press loading conditions and offers design recommendations to minimize spatial pressure concentrations. A pressure mat was used to assess the back-backrest interfacial pressure distribution of 15 subjects executing RT leg-presses at 50% body weight, over 16 different back-support geometries. Real-time forces, knee angles, and pressures were captured. The resulting data show that more prominent (≥2.1 cm) back-supports, positioned 19 cm above the seat pan typically produced greater peak pressures (41.8 ± 7.2 kPa). Conversely, less prominent supports (∼0.7 cm) generally achieved lower peak pressures (with greater distribution). Our data suggest that the most prudent choice for fixed-shape backrests to best distribute interfacial pressure on leg-press devices is to incorporate shallow convex supports (∼0.7 cm) and locate them away from P = 19 cm. The result is surprising as this prominence location is a common ergonomic feature. If an adjustable backrest is considered, peak pressures may be reduced by up to 26 ± 8% (9.7 ± 3.1 kPa) compared to flat geometries.ISSN:0148-0731ISSN:1528-895