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Effects of the maximum soil aggregates size and cyclic wetting–drying on the stiffness of a lime-treated clayey soil / A. M. Tang in Géotechnique, Vol. 61 N° 5 (Mai 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 5 (Mai 2011) . - pp. 421-429 Titre : Effects of the maximum soil aggregates size and cyclic wetting–drying on the stiffness of a lime-treated clayey soil Type de document : texte imprimé Auteurs : A. M. Tang, Auteur ; M. N. Vu, Auteur ; Y.-J. Cui, Auteur Année de publication : 2011 Article en page(s) : pp. 421-429 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Fabric/Structure  of  soil  Time  dependence  Suction  Soil  stabilisation  Laboratory  tests  Stiffness Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Lime treatment is a well-known technique to improve the mechanical response of clayey subgrades of road pavements or clayey soils used for embankment. Several studies show that lime treatment significantly modifies the physical and hydromechanical properties of compacted soils. Nevertheless, studies on the scale effect under climatic changes are scarce. Actually, wetting–drying cycles might significantly modify the microstructure of treated soils, giving rise to changes in hydromechanical properties. This modification could be dependent on the size of soil aggregates before lime treatment. In the present work, this scale effect was studied by investigating the stiffness of a compacted lime-treated clayey soil using bender elements. The studied soil was first air-dried and ground into a target maximum soil aggregates size (D max). For each aggregate size, the soil was humidified to reach the target water contents w i, then mixed with 3% of lime powder (mass of lime divided by mass of dried soil) prior to the static compaction at a dry density of 1·60 Mg/m3. Two initial water contents (w i = 14 and 18%) and four maximum soil aggregates sizes (D max = 0·4, 1·0, 2·0 and 5·0 mm) were considered. After the compaction, the soil specimen (50 mm in diameter and 50 mm high) was covered by plastic film in order to prevent soil moisture changes. The soil stiffness was then monitored at variable time intervals until reaching stabilisation. Afterwards, the soil specimen was subjected to full saturation followed by air-drying to come back to its initial water content. The results show that: (a) the soil stiffness after lime-treatment is significantly dependent on the aggregate size: the finer the aggregates the higher the soil stiffness; (b) the effect of initial water content on the stiffness is negligible; and (c) the wetting–drying cycles seem to slightly increase the soil stiffness in the case of lime-treated specimens and decrease the soil stiffness in the case of untreated specimens. Furthermore, when an intensive drying was applied reducing the soil water content lower than the initial level, the soil stiffness decreased drastically after the subsequent wetting. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.sip11.005 [article] Effects of the maximum soil aggregates size and cyclic wetting–drying on the stiffness of a lime-treated clayey soil [texte imprimé] / A. M. Tang, Auteur ; M. N. Vu, Auteur ; Y.-J. Cui, Auteur . - 2011 . - pp. 421-429. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 5 (Mai 2011) . - pp. 421-429 Mots-clés : Fabric/Structure  of  soil  Time  dependence  Suction  Soil  stabilisation  Laboratory  tests  Stiffness Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Lime treatment is a well-known technique to improve the mechanical response of clayey subgrades of road pavements or clayey soils used for embankment. Several studies show that lime treatment significantly modifies the physical and hydromechanical properties of compacted soils. Nevertheless, studies on the scale effect under climatic changes are scarce. Actually, wetting–drying cycles might significantly modify the microstructure of treated soils, giving rise to changes in hydromechanical properties. This modification could be dependent on the size of soil aggregates before lime treatment. In the present work, this scale effect was studied by investigating the stiffness of a compacted lime-treated clayey soil using bender elements. The studied soil was first air-dried and ground into a target maximum soil aggregates size (D max). For each aggregate size, the soil was humidified to reach the target water contents w i, then mixed with 3% of lime powder (mass of lime divided by mass of dried soil) prior to the static compaction at a dry density of 1·60 Mg/m3. Two initial water contents (w i = 14 and 18%) and four maximum soil aggregates sizes (D max = 0·4, 1·0, 2·0 and 5·0 mm) were considered. After the compaction, the soil specimen (50 mm in diameter and 50 mm high) was covered by plastic film in order to prevent soil moisture changes. The soil stiffness was then monitored at variable time intervals until reaching stabilisation. Afterwards, the soil specimen was subjected to full saturation followed by air-drying to come back to its initial water content. The results show that: (a) the soil stiffness after lime-treatment is significantly dependent on the aggregate size: the finer the aggregates the higher the soil stiffness; (b) the effect of initial water content on the stiffness is negligible; and (c) the wetting–drying cycles seem to slightly increase the soil stiffness in the case of lime-treated specimens and decrease the soil stiffness in the case of untreated specimens. Furthermore, when an intensive drying was applied reducing the soil water content lower than the initial level, the soil stiffness decreased drastically after the subsequent wetting. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.sip11.005

Preliminary study on the mechanical behaviour of heat exchanger pile in physical model / A. Kalantidou in Géotechnique, Vol. 62 N° 11 (Novembre 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 11 (Novembre 2012) . - pp. 1047 –1051 Titre : Preliminary study on the mechanical behaviour of heat exchanger pile in physical model Type de document : texte imprimé Auteurs : A. Kalantidou, Auteur ; A. M. Tang, Auteur ; J. M. Pereira, Auteur Année de publication : 2012 Article en page(s) : pp. 1047 –1051 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Settlement  Soil/structure  interaction  Temperature  effects  Model  tests Résumé : The effects of temperature changes on the mechanical behaviour of heat exchanger piles need to be taken into account in geotechnical design. In this preliminary study, the behaviour of an axially loaded pile under thermal cycles was investigated using a physical model. After applying the axial load on the pile head, the pile was heated from 25°C to 50°C and subsequently cooled to 25°C. Four tests (corresponding to four values of axial load) were performed and two temperature cycles were undertaken in each test. The pile temperature and the pile head displacement were monitored. When low axial loads were applied, the heating induced heave and cooling induced settlement of the pile head. In this case, the displacement–temperature curve was found to be reversible and similar to the thermal expansion curve of the pile. However, in the case of higher axial loads, the heave of the pile head, obtained during heating, was lower than the thermal expansion of the pile, suggesting settlement of the pile toe. Irreversible settlement of the pile head was observed after these thermal cycles. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.T.013 [article] Preliminary study on the mechanical behaviour of heat exchanger pile in physical model [texte imprimé] / A. Kalantidou, Auteur ; A. M. Tang, Auteur ; J. M. Pereira, Auteur . - 2012 . - pp. 1047 –1051. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 11 (Novembre 2012) . - pp. 1047 –1051 Mots-clés : Settlement  Soil/structure  interaction  Temperature  effects  Model  tests Résumé : The effects of temperature changes on the mechanical behaviour of heat exchanger piles need to be taken into account in geotechnical design. In this preliminary study, the behaviour of an axially loaded pile under thermal cycles was investigated using a physical model. After applying the axial load on the pile head, the pile was heated from 25°C to 50°C and subsequently cooled to 25°C. Four tests (corresponding to four values of axial load) were performed and two temperature cycles were undertaken in each test. The pile temperature and the pile head displacement were monitored. When low axial loads were applied, the heating induced heave and cooling induced settlement of the pile head. In this case, the displacement–temperature curve was found to be reversible and similar to the thermal expansion curve of the pile. However, in the case of higher axial loads, the heave of the pile head, obtained during heating, was lower than the thermal expansion of the pile, suggesting settlement of the pile toe. Irreversible settlement of the pile head was observed after these thermal cycles. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.T.013