No description available.

Jusqu'à récemment dans de nombreuses régions tropicales et subtropicales, on utilisait surtout les graveleux latéritiques en géotechnique routière, comme matériaux d’assise de chaussée. Avec l'évolution des besoins, la récente prise en compte des contraintes environnementales et la rareté des graveleux latéritiques de bonne qualité, la promotion de matériaux dont l'usage est peu répandu pour diverses raisons techniques ou historiques est encouragée. En Afrique subsaharienne, la valorisation des matériaux marginaux naturels locaux, singulièrement les sols latéritiques fins, en technique routière est vivement encouragée pour une meilleure utilisation des ressources dans le cadre du développement durable et dans un contexte socio-économique particulier.Ce mémoire de thèse expose une étude du comportement mécanique d’un sol latéritique fin traité au ciment à différents dosages pour une valorisation en technique routière. Il comporte cinq parties:La première partie concerne une étude bibliographique des travaux réalisés sur les sols latéritiques. On présente également les travaux réalisés sur les sols traités au ciment.La deuxième partie est consacrée à la description des matériaux étudiés. Après la présentation des caractérisations physiques, chimiques et minéralogiques de ces matériaux, on présente les paramètres de l’étude. Cette partie s’achève par la caractérisation minéralogique et microstructurale du sol latéritique traité au ciment à différents dosages.La troisième partie présente les résultats expérimentaux d’une étude de la consolidation unidimensionnelle du sol latéritique avant et après traitement au ciment à différents dosages. La vérification de l’aptitude au traitement du sol, la détermination des caractéristiques intrinsèques et de compactage du sol traité au ciment sont également présentées dans cette partie.La quatrième partie présente les résultats expérimentaux de la résistance mécanique du sol avant et après traitement au ciment. La portance, les résistances en compression et en traction, les résistances à la rupture et au cisaillement forment l’ossature de cette partie.Enfin la cinquième partie présente une analyse numérique et économique de la conception d’une assise de chaussée en sol latéritique traité au ciment à différents dosages L’influence du traitement du sol sur l’épaisseur de l’assise de chaussée est examinée, ainsi que le coût économique de l’assise de chaussée. / Until recently, in many tropical and subtropical regions, lateritic gravels have been used in geotechnical highway, like for example in the road foundations. With the increase of needs, the recent consideration of environmental constraints and the unavailability of lateritic gravels with good mechanical properties, the promotion of materials whose use is not widespread for various technical or historical reasons is encouraged. In Sub-saharan Africa, the valorization of local natural marginal materials particularly the fine grained lateritic soils, in road construction purposes is strongly encouraged where a better utilization of resources might help insure sustainable development in a particular socio-economic context.This thesis presents a study of the mechanical behavior of a cement treated fine grained lateritic soil for a valorization in road construction. It constains five parts:The first part concerns a literature review of work on lateritic soils. It also presents the work completed on soils treated with cement.The second part is devoted to the description of the materials studied. After the presentation of physical, chemical and mineralogical characterizations of these materials, we present the parameters of the study. At the end, mineralogical and microstructural characterization of cement treated lateritic at different dosages is presented.The third part presents the experimental results of a study of one-dimensional consolidation of lateritic soil before and after treatment with cement at different dosages. The verification of the processability of the soil, as well as the determination of intrinsic characteristics and compaction of the cement treated lateritic are also illustrated in this section.The fourth part shows the experimental results of the mechanical strength of the lateritic soil before and after treatment with cement. The discussion about bearing capacity, the compressive and tensile strength and the rupture and shear strengths constitutes the major concern of this part.Finally, the fifth part presents a numerical and economic analysis of the design of a road foundation of lateritic soil treated with cement at different dosages. The influence of soil treatment on the thickness of the road foundation is examined, as well as the economic cost of the road foundation.

Little effort has been made to apply the Critical State Soil Mechanics concept to the prediction of pavement response. The aim of this research is to apply soil mechanics principles, particularly the kinematic hardening concept, to the prediction of the response of lightly trafficked pavements to repeated loading. For this purpose, the finite element critical state program CRISP is used. A comparison is made between the predictions given by the three-surface kinematic hardening (3-SKH) model and a layered elastic analysis BISAR for the resilient deformation produced by repeated loading of a thinly surfaced pavement, and the models are found to be in good agreement. The ability of the 3-SKH model to predict soil behaviour under cyclic loading, and under one-dimensional loading, unloading and reloading is also evaluated. A comparison between model predictions and experimental data obtained by other researchers shows that the 3-SKH model over-predicts the value of K0,nc and hence shear strain during monotonic loading. This problem is magnified when the model is applied to cyclic loading behaviour where large numbers of cycles are involved. The model also predicts an accumulation of negative shear strain with increasing number of cycles under some stress conditions. This will lead to unrealistic predictions of rutting in pavements. However, the model is suitable for obtaining resilient parameters for input to a layered elastic analysis program. A new model, which is a modified version of the 3-SKH model, is therefore proposed by modifying the flow rule and the hardening moduli. This model can correctly predict the value of K0,nc and reduce the amount of shear strain predicted. The model also eliminates the problem of accumulation of negative shear strain with increasing number of cycles. The new model introduces two additional parameters, one of which can be determined by one-dimensional normal compression test, and the other by fitting a set of cyclic loading data. The new model is used to design the required thickness of granular material using the permissible resilient subgrade strain and permanent rut depth criteria during construction. It is found that the new model predicts a realistic granular layer thickness required to prevent excessive rutting, thus showing much promise for use in design of thinly surfaced pavements.