En France, le système de stockage profond de déchets radioactifs envisagé est constitué d’une barrière naturelle (roche hôte argileuse, argilite) et de barrières artificielles, comprenant des bouchons d’argile gonflante (bentonite)-sable pour son scellement. L'objectif de cette thèse est d’étudier l’efficacité du gonflement et du scellement des bouchons placés dans l’argilite, sous l’effet, à la fois, d’une pression d’eau et d’une pression de gaz (tel que formé dans le tunnel). Pour évaluer la capacité de scellement du bouchon bentonite/sable partiellement saturé en eau, on a évalué sa perméabilité au gaz Kgaz sous pression de confinement variable (jusqu’à 12MPa). L'étanchéité au gaz (Kgaz < 10-20m2) est obtenue sous confinement Pc≥9MPa si la saturation est d’au moins 86-91%. Par ailleurs, nous avons évalué le gonflement et l'étanchéité du bouchon de bentonite-sable imbibé d’eau dans un tube d’argilite ou de Plexiglas-aluminium lisse ou rugueux. La présence de gaz diminue la pression effective de gonflement (et la pression de percée de gaz) à partir d’une pression Pgaz= 4 MPa. Après saturation complète en eau, l’écoulement continu de gaz au travers du bouchon seul se fait à Pgaz=7-8MPa s’il dispose d’une interface lisse avec un autre matériau (tube métallique), alors que celui au travers de l’ensemble bouchon/argilite a lieu à Pgaz=7-7,5MPa. Le passage à travers le bouchon gonflé au contact d’une interface rugueuse se fait à une pression de gaz bien supérieure à la pression de gonflement du bouchon. Les essais de percée de gaz montrent que l'interface et l'argilite sont deux voies possibles de migration de gaz lorsque l’ensemble bouchon/roche hôte est complètement saturé / In France, the deep underground nuclear waste repository consists of a natural barrier (in an argillaceous rock named argillite), associated to artificial barriers, including plugs of swelling clay (bentonite)-sand for tunnel sealing purposes. The main objective of this thesis is to assess the sealing efficiency of the bentonite-sand plug in contact with argillite, in presence of both water and gas pressures. To assess the sealing ability of partially water-saturated bentonite/sand plugs, their gas permeability is measured under varying confining pressure (up to 12MPa). It is observed that tightness to gas is achieved under confinement greater than 9MPafor saturation levels of at least 86-91%. We than assess the sealing efficiency of the bentonite-sand plug placed in a tube of argillite or of Plexiglas-aluminium (with a smooth or a rough interface). The presence of pressurized gas affects the effective swelling pressure at values Pgas from 4MPa. Continuous gas breakthrough of fully water-saturated bentonite-sand plugs is obtained for gas pressures on the order of full swelling pressure (7-8MPa), whenever the plug is applied along a smooth interface. Whenever a rough interface is used in contact with the bentonite-sand plug, a gas pressure significantly greater than its swelling pressure is needed for gas to pass continuously. Gas breakthrough tests show that the interface between plug/argillite or the argillite itself are two preferential pathways for gas migration, when the assembly is fully saturated

This dissertation on American imperialism toward Côte d’Ivoire challenges mainstream theories in International Relations. It argues that in order to understand imperialism, we must understand the ontology of the power at work and of states mediating the global capitalism and the historical context. Following Robert Cox’s and Alejandro Colás’ works, it suggests broadening our comprehension by reconnecting imperialism to empire. The framework reveals that imperialism is not just naked brigandage, nor selfish expansion of culture or power. The thesis argues an imperial market security politics historically engaged into the restoration of the modern sovereignty of failed states and regulation of their regime, economy and culture. Through a historical study of the American case in Côte d’Ivoire, the dissertation finds that its dominion of the structures of security, knowledge and market makes the United States of America an empire attuned to the postcolonie era with authority to dictate the rules of the game. It also finds that Côte d’Ivoire is a failed state. American led-globalization runs up against the colonial pact which makes France the owner. Subverting modern capitalism, contestations against the democratic transition regime and France supporting the statu quo ante crush down into civil war and the disruption of Côte d’Ivoire’s sovereignty in an age of terror. The United States' Government implements Peace and security, Investing in People, Governing Justly and Democratically and People-to-People. It also dictates the agenda to restore Côte d’Ivoire’s sovereignty: electoral legitimacy of rulers and constitutional breakthrough. These global programs and agenda spread out in Côte d’Ivoire, public goods historically fostered by empires: the condition of stability, legitimate authority, and sense of belonging.