[pt] Os reservatórios de hidrocarbonetos em rochas carbonáticas representam aproximadamente 50 por cento da produção mundial de petróleo e tem por característica marcante sua complexidade, uma vez que são bastante heterogêneos. No Brasil, as rochas carbonáticas ganharam uma grande importância com a descoberta dos reservatórios carbonáticos do pré-sal. Entender e caracterizar estes reservatórios, que apresentam baixas taxas de penetração, exigirá grandes esforços em pesquisa e desenvolvimento. Uma pequena contribuição neste sentido é proporcionada nesta dissertação, onde três distintas rochas carbonáticas, o travertino romano, o travertino turco e o travertino de Itaboraí, foram caracterizadas geológica e geomecanicamente. O programa experimental consistiu na caracterização mineralógica, química, textural e diagenética, bem como na realização de ensaios de resistência e de porosidade. De posse dos resultados do programa experimental buscou-se correlações entre os índices/propriedades/parâmetros determinados. Verificou-se que a resistência à compressão simples dos materiais é diretamente proporcional, a sua densidade, a sua velocidade de propagação de ondas e ao índice esclerométrico; e inversamente proporcional a sua porosidade. Constatou-se ainda que a velocidade de propagação de ondas dos materiais é diretamente proporcional a sua densidade e inversamente proporcional a sua porosidade. / [en] Hydrocarbon reservoirs in carbonate rocks represent circa 50 percent of all oil produced worldwide. Those reservoirs are very complex since they are quite heteregeneous. In Brazil, carbonate rocks gained a great importance with the discovery of the pre-salt reservoirs. Understand and characterize these reservoirs, that present low penetration rates, will require major efforts in research and development. A small contribution in this regard is provided in this dissertation, where three travertines (i.e., Roman, Turkish and Itaboraí) were geologically and geomechanically characterized. The experimental program consisted in the chemical, mineralogical, textural and diagenetic characterization, as well as strength and porosity tests. A comprehensive analysis of test results from the experimental program was carried out in order to seek correlations between the indexes/properties/parameters determined. It was found that the unconfined compression strength of materials is directly proportional to its density, its velocity of ultrasonic wave propagation and to Schmidt test hammer index; and inversely proportional to its porosity. It was also found that the velocity of ultrasonic wave propagation of materials is directly proportional to its density and inversely proportional to its porosity.

Le renforcement des fondations par soil mixing consiste à créer dans le sol des colonnes à module mixte obtenues en mélangeant le sol sur place avec un liant hydraulique. Ces colonnes, qui possèdent des caractéristiques mécaniques entre celles du béton et celles du sol, permettent d’améliorer la portance du sol d’assise et réduire les tassements excessifs des structures surjacentes. Ce travail de recherche consiste en une étude du comportement des fondations superficielles renforcées par des colonnes de soil mixing. Il vise à mettre en exergue les améliorations que cette technique apporte en termes d’augmentation de la capacité portante et de réduction des tassements. Dans une première étape, un matériau de soil mixing est formulé à partir d’un sable d’Hostun et d’un ciment CEM III. Une étude préalable a été réalisée pour déterminer les caractéristiques mécaniques de ce matériau de soil mixing, du sable d’Hostun, ainsi que les propriétés d’interface sable d’Hostun - soil mixing. Dans une seconde étape, une cuve expérimentale a été conçue pour permettre la réalisation de la procédure expérimentale du renforcement du sable par des colonnes de soil mixing. Plusieurs configurations du modèle physique ont été testées: Il s’agit d’essais de chargement sur fondations superficielles reposant sur un massif renforcé ou non. La taille de la semelle, le nombre des colonnes de renforcement, leurs âges, la densité de sol ainsi que le type de renforcement (renforcement type fondation mixte ou inclusion rigide) sont des paramètres dont l’effet a été étudié. Les essais de caractérisation, la conception du modèle expérimentale ainsi que les essais de chargement réalisés ont permis de mieux comprendre le comportement du sol renforcé. La connaissance des paramètres géomecaniques du sol et du matériau de soil mixing a permis de comprendre l’évolution de la capacité portante des semelles en présence des colonnes de renforcement. La présence d’un horizon porteur dans lequel les colonnes sont encastrées fait augmenter significativement la capacité portante de la semelle. Dans le cas du renforcement type inclusions rigides, l’augmentation de l’épaisseur du matelas granulaire réduit la capacité portante de la semelle renforcée. Cependant, elle fait augmenter la contribution des colonnes de renforcement dans la reprise des efforts appliqués sur la semelle. Une confrontation a été réalisée entre les résultats expérimentaux des essais de chargement et les résultats provenant d’un modèle éléments finis mis en œuvre avec le logiciel Abaqus. Les paramètres utilisés proviennent de nos essais de caractérisation réalisés dans le cadre de cette étude. Le modèle a présenté des résultats satisfaisant et a réussi de reproduire le comportement physique des semelles renforcées. Le modèle n’a non seulement réussi à reproduire les essais de chargement à l’échelle d’une colonne, mais aussi à l’échelle des semelles renforcées par une seule colonne et par quatre colonnes. / The reinforcement of shallow foundations by soil mixing consists on mixing the soil beneath with a hydraulic binder in order to obtain columns with mixed modulus. These columns, which have mechanical properties bounded between those of concrete and those of soil, can improve the soil bearing capacity and reduce excessive settlements as well. This research work is a phenomenological and quantitative study of the behavior of shallow foundations reinforced by soil mixing columns. It leads to analyze and highlight improvements that this technology brings in terms of bearing capacity increase and settlement reduction. In a first step, a soil mixing material is formulated from Hostun sand and cement CEM III. A preliminary study is conducted to determine the mechanical characteristics of the soil mixing material, Hostun sand and sand – soil mixing interface. In a second step, an experimental tank is designed to allow the installation of 1 m3 of hostun sand under different density. The experimental procedure allows also the installation of soil mixing columns that reinforce the soil. Finally a device is installed in order to carry on loading tests. Different configurations of the physical model were tested. Loading tests are carried on soil mixing columns and on unreinforced and reinforced shallow foundations. Size of the foundation, number of reinforcing columns, their age, soil density and type of reinforcement (rigid inclusion or mixed foundation) are parameters we change during this study. The characterization tests, the design of the experimental model, and the loading tests helped us to better understand the behavior of the reinforced soil. The knowledge of geomechanical parameters of soil and soil mixing material allowed us to understand the evolution of the bearing capacity of the reinforced foundations. The presence of a carrier horizon, in which the tip columns is embedded, leads to significantly increase the bearing capacity of the foundation. In the rigid inclusions reinforcement case, the increasing of granular mattress thickness reduces the bearing capacity of the reinforced foundation. However, it increases the part of the loading transmitted to soil mixing columns. A comparison was made between the experimental results of loading tests and the results of a finite element model implemented with Abaqus software. Model parameters are taken from our material characterization study. It is proven that the model developed is able to reproduce not only loading tests at column scale, but alsot at reinforced foundations scale.