In this paper, modal responses of the Brezina concrete arch dam, Algeria, are determined using the finite elements commercial packages ANSYS. To study the effects of the foundation soil, three 3D models have been created, the dam alone without soil, the dam-massless soil and the dam-soil with soil mass model. Moreover, a parametric study of the viscous damping, in Raleigh form, has been conducted. It is found that the natural frequencies of either undamped or damped modes obtained from the dam-soil with soil mass model are drastically lower compared to that of the dam alone model, and are markedly lower than those obtained from the dam-massless soil model. Likewise, similar comparisons have been observed for the damping quantities, in absolute values, between the three models. An in-depth review of the literature reveals that the study carried out herein constitutes several elements of originality as only very few similar work have been undertaken.
Swelling and shrinkage of expansive soils occur mainly due to a change in the moisture regime and pose serious problems to foundations causing damage to structures founded on them. However, construction on this type of soil requires a good companion for the recognition of identification, characterization of their swelling potential and Treatment processing.In this work we are interested by two aspects:1) The first is on the tests recommended for the identification of diferants expansive soils in the region of Tlemcen in the north western Algeria.2) The second is to perform stabilization tests on remolded samples by salts (KCl Potassium Chloride, Magnesium Chloride MgCl 2 ) with deffrants concentrations and see their influence on physic-chemical parameters and swelling.The results obtained show that stabilization by the addition of salts modifies the physico-chemical characteristics of soil and the results are quite satisfactory in significantly reducing the phenomenon of swelling, as regards the effect of salt on the swelling pressure it varies from salt to another and concentration to another.
Soil liquefaction is the source of several major damages during earthquakes on the material and human level. Several authors have studied the probability of liquefaction by in situ and laboratory tests and several models have been proposed to calculate the safety factor. But because of various uncertainties in performance function parameters, we adopted in this paper a reliability analysis that considers uncertainties of parameters and model uncertainties. We used the Monte Carlo simulation (MCS) to calculate the probability of failure to liquefaction based on standard penetration test SPT which soil's parameters are modeled by random variables.The reliability results obtained show that the variability of soil's parameters has an important impact on the probability of liquefaction. A sensitivity analysis based on the coefficient of variation is presented to see the effect of each random variable on the probability of liquefaction.
RésuméL'article examine le développement des recherches sur la prise en compte des incertitudes dans l'analyse de la fiabilité des barrages en terre.Après avoir souligné l'importance des ruptures, les auteurs montrent le poids particulier des incertitudes sur les terres pour les deux principaux états criti ques (érosion et stabilité) et donnent une illustration détaillée pour l'érosion interne. Ensuite, plusieurs techniques sont mises en oeuvre pour mesurer, modéliser et contrôler les aléas sur les terres : l'analyse factorielle pour contrôler les zones d'emprunt, l'analyse de variance-covariance pour réduire les aléas sur les para mètres de projet et les modéliser, la géostatistique pour contrôler le compac tage des terres et tenir compte de la position géographique des aléas. Toutes ces techniques contribuent à mieux connaître et prendre en compte la succes sion des incertitudes et des erreurs. Enfin, les auteurs indiquent l'absence, malheureusement encore, de méthodes opérationnelles pour calculer le rôle de ces incertitudes et erreurs sur le résul tat final. C'est dans ce sens que les efforts doivent aller.
AbstractThis paper examines the current research developments on uncertainty factors which play a crucial role in the analysis of earth dams reliability. In emphasizing the importance of failure, the authors underline the particular role played by uncertainty on earth properties for 2 principal critical states (ero sion and stability). A detailed illustration of internal erosion is also presented. In order to measure, modelise and control the hazards of earth, the following techniques are used : factorial analysis in order to control the borrow areas and the significance of the test samples, variance-covariance analysis in order to reduce hazards and modelize design parameters, geostatistics in order to con trol earth compaction and to take into account the geographic position of hazards. All of these techniques will contribute to a better understanding and manipulation of successive uncertainties and errors. Finally, the authors suggest some possibilities of where future research should be oriented in order to develop operational methods for calculation the role of uncertainties and errors.
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