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The disorders caused by the swelling of the soil on the structures have been observed for several years in the city of Rufisque. This article presents the results of the study of swelling kinetics of expansive soils in Rufisque and their prediction based on the hyperbolic rule. The odometer is used as an instrument for measuring swelling and the tests are carried out on some intact samples at their sampling water content. The present study shows that in Rufisque the most swelling layer is marl. The results show two phases of development. The first phase is very fast and represents 77% of the final deformation and the second one is slower. The prediction of the issue by the hyperbolic rule shows that it underestimates the first phase but gives a good prediction of the second phase of the swelling rate. There is a good correlation between the final swelling rates. However, the model gives a bad approximation of the half-swelling time.

This paper discusses the possibility to use CBR moduli, as deduced from CBR penetration curves, as parameters for the design of pavements. Series of CBR tests on compacted lateritic samples are analysed. These moduli, determined on soaked compacted samples, are compared with subgrade and resilient moduli of various types of materials from literature. The influence of water content in laboratory tests and full scale structures may play a significant role. CBR moduli offer an alternative to other ways of assessing the stiffness of pavement underlying layers. Experimental data on the relations of CBR index, CBR modulus, particle size distribution and optimum Proctor density are presented and discussed.

In earthworks engineering, predicting the influence of the water content and the dry density on compacted soils deformation is a fundamental issue, which is particularly important for the use of clays in embankments. This paper presents the experimental results and a microstructural interpretation of swelling tests performed on four clays, compacted at different water contents and dry densities. The influences of dry density and water content on the swelling potential are described, showing the coupled effect of these two parameters. In order to quantify this coupling, the initial air void ratio is defined and it is observed that this air void ratio has an apparent linear relationship with the void ratio after swelling. This observation enables analysing all the tests in a synthetic manner, by plotting the origin ordinate and the slope of the linear relationships versus the initial hydrous state. Moreover, one of the clays microstructure was analysed using mercury intrusion porosimetry (MIP). The results show that swelling leads to a micropores increase and a macropores decrease. In addition, micropores volume increase does not depend on the initial dry densities, whereas the macropores volume increase does. For further discussion, a simplified microstructural model is proposed allowing the interpretation of the soil swelling using MIP results. The comparison between the model prediction and the microstructure observation supports the interpretation of the swelling tests and shows that the origin ordinate and the slope of the relationship between the initial air void ratio and the final void ratio can be linked to micropores and macropores volume variations. However, the comparison also shows that the simplified microstructural model presents some limitations when applied to very dry or wet soils.

Wetting-induced deformations of compacted fine-grained soils are of particular interest in earthworks engineering, where embankment design needs to take into account potential future water-content variations. The influence of compaction rate on swelling potential and, more generally, wetting-induced deformations are analyzed in this paper on the basis of an original physical microstructural model. The interpretation of macroscopic experimental results obtained on a high-plasticity clay and a silty clay shows that the model enables quantitative description of intra- and inter-aggregate pore volume changes due to wetting. Using this approach, a fundamental difference was observed between the high-plasticity clay and the silty clay in wetting tests under vertical stress: tests performed on the high-plasticity clay can be analyzed using a microstructural model, whereas this model is not relevant for the analysis of silty clay behaviour, which is better interpreted in the framework of a conventional elastoplastic model. The interpretations were compared to microstructure observations, which support the main tendencies deduced from the model.

Les symboles et unites recommandes pour le traitement des problemes de resistance au cisaillement ont ete definis par la Societe Internationale de Mecanique des Sols et des Travaux de Fondations * Mecanique des sols- Symboles, unites et definitions .