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La stabilité des infrastructures est un souci majeur pour différentes raisons économiques, écologiques ou, plus important, la sécuritédes batiment. Ceci peut se faire par différentes techniques, mécanique, chimique ou les deux à la fois, afin d’améliorer les propriétésgéotechniques des sols instables. Les techniques utilisées sont les ajouts, dont les plus courants sont la chaux et le ciment. Cette étude a pour objet de déterminer l’évolution des propriétés géotechniques d’un sol schisteux du pôle universitaire d’El-Aouana dans la wilaya de Jijel (Algérie). L’échantillon prélevé sur site a été modifié avec des proportions d’additifs avec 0, 1 %, 3 % et 7 % du remplacement du ciment et de la chaux en poids sec afin de tester les différents proprietées de la patte fraiche du sol argileux.On conclut que l’addition d’un liant (Ciment ou chaux) au sol schisteux provoque une réduction de la plasticité, une amélioration des caractéristiques de compactage au Proctor, une augmentation rapide de l’indice de portance immédiat en fonction du traitement et une augmentation de la cohésion et de l’angle de frottement.

The stability of infrastructure is a major concern for various economic, ecological or, more importantly, the security of buildings. This can be done by different techniques, mechanical, chemical or both, to improve the geotechnical properties of unstable soils. The techniques used are the additions, of which, the most common are lime and cement.. The purpose of this study is to determine the evolution of the geotechnical properties of a shale soil of the university center of El-Aouana in the wilaya of Jijel (Algeria). The sample taken on site was modified with additives proportions, 0, 1 %, 3% and 7% of the replacement of cement and lime in dry weight in order to test the different properties of the fresh paw of clay soil. Finally, on conclude that the addition of a binder (Cement or lime) to shale soil causes a reduction in plasticity, an improvement in compaction characteristics with Proctor, a rapid increase in the immediate lift index depending on the treatment. and an increase in cohesion and the angle of friction. [ABSTRACT FROM AUTHOR]

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Copyright of Politique Étrangère is the property of Institut Francais des Relations Internationales and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fossil-bearing shale specimens that include sulfides in their compositions are chemically reactive and sometimes also mechanically fragile. This decay is often related to iron sulfate efflorescence resulting from the oxidation of sulfide compounds. The processes underlying these degradations are poorly known, thus impeding the elaboration of curative or preventive treatments. The present contribution aims to identify the origin of museum specimen alterations. It focuses on the Flouest collection housed at the Muséum National d’Histoire Naturelle (MNHN, Paris, France) and originating from the Autun Basin (Saône-et-Loire, France, Permian). To evaluate the alteration of MNHN specimens, it appeared necessary to compare their composition with that of unaltered shale so as to identify chemical changes occurring during ageing. Therefore, new material was collected in the Autun Basin, among others on the locality of Muse that corresponds to the same lithostratigraphic unit as that of the MNHN specimens. This material was, if necessary, artificially aged. The first part of this work, presented elsewhere, deals with the use of X-ray diffraction and Mössbauer spectroscopy for characterizing iron reactivity and speciation. It leads to the conclusion that the reactivity of iron in the shale matrix was limited and could not account for the large efflorescence of iron (II) sulfate occurring nearby the fossil. The second part presented here focuses on the use of S K-edge X-ray Absorption Near Edge Structure (XANES) spectroscopy for characterizing sulfur speciation and reactivity. Measurements were performed on the shale matrix and on thin layers of maceral found in the proximity of damaged areas. As sulfur may be found in association with calcium or organic matter, complementary techniques were implemented, such as FTIR spectroscopy, Rock-Eval pyrolysis (characterization of organic matter content) and Ca K-edge XANES (analysis of calcium speciation) spectroscopy. It was shown that sulfur is mainly related to thioether, sulfoxide, iron sulfide, and sulfates whereas calcium is mainly bound to carboxylate, carbonate and/or sulfate groups. FTIR analysis of the macerals confirmed the presence of vitrinite on damaged MNHN specimens. The low oxygen content of new shale samples determined by Rock-Eval pyrolysis indicates that the organic matter is well preserved, despite the fact that samples come from outcrop surface. In the newly collected material, sulfur is mainly related to organic sulfides (thioether) with a minor occurrence of iron sulfide. In the shale fraction of damaged MNHN specimens, sulfur is mostly oxidized into a mixture of iron and calcium sulfate. However, in the vitrinite layers of the same specimens, a large proportion of sulfur corresponds to organic sulfides. Also the oxidation of sulfur does not occur homogeneously but preferentially in the shale fraction, probably because this latter is porous whereas vitrinite is not. Artificial ageing of new shale material showed that the oxidation of organic sulfides could be reproduced at 90 °C, 80% of relative humidity. However, the obtained efflorescence almost exclusively corresponds to calcium sulfate whereas iron (II) sulfates are mostly observed on MNHN specimens. The new material collected on site is probably to be questioned, and future studies will have to select new samples with fossil remains. This will be the object of the third part of this work. [ABSTRACT FROM AUTHOR]