This paper presents the findings of a laboratory investigation of the thermomechanical behaviour of clayey soils. The tests were performed on reconstituted and natural clayey soils using triaxial cells modified to control temperature. The range of temperatures that were investigated is from 20°to 60°C. The thermal behaviour of the clays and the influence of temperature on their mechanical behaviour were investigated separately. The analysis of the experimental results obtained in drained and undrained nonisothermal tests and during thermal consolidation made it possible to identify a link between the thermal and the time-dependent behaviour of the soil skeleton. Therefore, as for creep processes, the response of the soil to thermal loading is not unique but among other factors depends strongly on the overall and recent stress history experienced by the soil. In the range of temperatures investigated, the deformability and strength of the soil were found to be relatively independent of temperature. Stiffening of the soil results from thermal cycles.Résumé : Cet article présente les résultats d'une étude en laboratoire du comportement thermo-mécanique des sols argileux. Les essais ont été réalisés sur des sols argileux naturels et reconstitués dans des cellules triaxiales modifiées pour contrôler la température. La plage des températures qui ont été étudiées varie de 20°C à 60°C. Le comportement thermique des argiles et l'influence de la température sur leur comportement mécanique ont été étudiés séparément. L'analyse des résultats expérimentaux obtenus dans des essais non isothermiques drainés et non drainés, et durant la consolidation thermique, a permis d'identifier un lien entre les comportements du squelette du sol dépendant du temps et de la température. En conséquence, en ce qui concerne les processus de fluage, la réponse du sol au chargement thermique n'est pas unique, mais dépend fortement entre autres facteurs des histoires récente et complète des contraintes qu'a vécues le sol. L'on a trouvé que dans la plage des températures étudiées, la déformabilité et la résistance du sol sont relativement indépendantes de la température. La rigidité du sol est augmentée par les cycles thermiques.

This paper illustrates an approximate procedure for the evaluation of the damage induced on existing buildings by the excavation of a tunnel. The method hinges on the development of a simplified structural model of the building, that can be readily incorporated into the finite-element mesh used to simulate the excavation of a tunnel. A first part of the article is devoted to the description of the equivalent structure and to the illustration of an identification procedure for the evaluation of its mechanical properties, based on appropriate scaling of the areal and inertial characteristics of the parent building. Then, the practical use of the method is illustrated by carrying out a series of three-dimensional numerical analyses of the excavation of an EPB tunnel, that include either the simplified or the fully detailed structural model of a masonry building. Using the results obtained with the complete building as a reference, it is shown that the simplified formulation is quite effective in capturing the main features of the soil-structure interaction for the problem at hand. Cases in which the method is less successful are discussed as well, indicating a suitable adjustment of the identification procedure for the simplified structural model

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This paper describes the main findings of a laboratory study on the mechanical behaviour of cemented geologically normally consolidated lacustrine clayey soils from two sites, Bacinetto (BA) and Avezzano (AZ), in the Fucino basin (Italy). One-dimensional and triaxial compression tests were carried out in order to investigate the effects of the presence and of the progressive degradation of the interparticle cementation bonds. The two tested soils showed quite different physical and mechanical properties, the more apparent ones being plasticity and yield stress values. The experimental results allowed the gross yield curves and the critical state conditions to be identified for both soils (BA clay and AZ silt). A number of typical features generally exhibited by cemented soils were clearly apparent: yield stresses greater than the in situ stress states, both soils being geologically normally consolidated; high values of compressibility index after yielding, which gradually reduce with increasingly applied stresses; strength reductions associated with a globally contractive behaviour. A convenient normalisation of the experimental results, in which the critical state conditions are assumed as a reference state, allowed the effects of cementation bonds and of their progressive degradation to be highlighted. In particular, BA samples were found to be characterised by different structures related to different degrees of cementation. Furthermore, despite the larger values of the yielding stresses exhibited by AZ silt, stronger effects of cementation are apparent in BA soil. Experimental results seem to indicate that at high values of the applied stress and strain paths, when bonds are largely damaged, the structures of the natural and parent reconstituted BA soil continue to be different. © 2010 Springer Science+Business Media B.V

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