Documents disponibles écrits par cet auteur

Compression behaviour of natural and reconstituted clays / Z.-S. Hong in Géotechnique, Vol. 62 N° 4 (Avril 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 291–301 Titre : Compression behaviour of natural and reconstituted clays Type de document : texte imprimé Auteurs : Z.-S. Hong, Auteur ; L.-L. Zeng, Auteur ; Y.-J. Cui, Auteur Année de publication : 2012 Article en page(s) : pp. 291–301 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Clays  Compressibility  Laboratory  tests Résumé : The intercept of the l o g ( 1 + e ) – l o g σ ′ v straight line is introduced to describe the effect of the starting point on the compressibility of natural and reconstituted clays. It is found that when the effective stress exceeds the remoulded yield stress, the compression behaviour of reconstituted clays is controlled solely by the water content at the remoulded yield stress and the liquid limit. Comparison of the compression behaviour of natural and reconstituted clays indicates that their difference in compressibility is caused by soil structure and the difference in water content at the compression starting point. The compression behaviour of natural clays can be classified into three regimes: (a) the pre-yield regime, characterised by small compressibility, with soil structure restraining the deformation up to the consolidation yield stress; (b) the transitional regime, characterised by a gradual loss of soil structure when the effective stress is between the consolidation yield stress and the transitional stress; and (c) the post-transitional regime, characterised by the same change law in compression behaviour as reconstituted clays when the effective stress is higher than the transitional stress. For the investigated clays, the transitional stress is 1·0–3·5 times the consolidation yield stress. The compression index varies solely with the void ratio at an effective stress of 1·0 kPa for both natural clays in the post-transitional regime and reconstituted clays when the effective stress exceeds the remoulded yield stress, and when compressed in such cases the compression curves of both natural clays and reconstituted clays can be well normalised to a unique line using the void index. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4# [article] Compression behaviour of natural and reconstituted clays [texte imprimé] / Z.-S. Hong, Auteur ; L.-L. Zeng, Auteur ; Y.-J. Cui, Auteur . - 2012 . - pp. 291–301. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 291–301 Mots-clés : Clays  Compressibility  Laboratory  tests Résumé : The intercept of the l o g ( 1 + e ) – l o g σ ′ v straight line is introduced to describe the effect of the starting point on the compressibility of natural and reconstituted clays. It is found that when the effective stress exceeds the remoulded yield stress, the compression behaviour of reconstituted clays is controlled solely by the water content at the remoulded yield stress and the liquid limit. Comparison of the compression behaviour of natural and reconstituted clays indicates that their difference in compressibility is caused by soil structure and the difference in water content at the compression starting point. The compression behaviour of natural clays can be classified into three regimes: (a) the pre-yield regime, characterised by small compressibility, with soil structure restraining the deformation up to the consolidation yield stress; (b) the transitional regime, characterised by a gradual loss of soil structure when the effective stress is between the consolidation yield stress and the transitional stress; and (c) the post-transitional regime, characterised by the same change law in compression behaviour as reconstituted clays when the effective stress is higher than the transitional stress. For the investigated clays, the transitional stress is 1·0–3·5 times the consolidation yield stress. The compression index varies solely with the void ratio at an effective stress of 1·0 kPa for both natural clays in the post-transitional regime and reconstituted clays when the effective stress exceeds the remoulded yield stress, and when compressed in such cases the compression curves of both natural clays and reconstituted clays can be well normalised to a unique line using the void index. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4#

Compression behaviour of reconstituted soils at high initial water contents / Z.-S. Hong in Géotechnique, Vol. 60 N° 9 (Septembre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 9 (Septembre 2010) . - pp. 691-700 Titre : Compression behaviour of reconstituted soils at high initial water contents Type de document : texte imprimé Auteurs : Z.-S. Hong, Auteur ; J. Yin, Auteur ; Y.-J. Cui, Auteur Année de publication : 2011 Article en page(s) : pp. 691-700 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Laboratory  equipment  Compressibility  Clays  Suction  pressure  Laboratory  tests Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Oedometer tests starting from a very small effective vertical stress of 0·5 kPa were performed on three reconstituted clays with different liquid limits. The soils were prepared at various initial water contents, ranging from 0·7 to 2·0 times their corresponding liquid limits. It is observed that the e–log σ ′ v compression curves show an inverse ‘S' shape due to suction pressure resisting deformation, similar to that of soft natural clays caused by consolidation yield stress. The suction pressure σ ′ s of the reconstituted clays can be correlated with the ratio of initial void ratio to void ratio at liquid limit e 0/e L. The suction pressure curve defined by a unique relationship between suction pressure σ ′ s and the normalised void ratio at suction pressure e s/e L is also proposed to distinguish between the pre-suction and the post-suction states. In addition, Burland's concept of the intrinsic compression line is adopted for correlating the compression curves of various reconstituted clays at high initial water contents. It has been found that the void index is a powerful parameter for normalising the compression curves in the post-suction state. Nevertheless, it seems that Burland's intrinsic compression line slightly underestimates the void index at the low stresses considered in this study. An extended intrinsic compression line is then derived in order to better fit the data for stresses lower than 25 kPa. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.09.p.059 [article] Compression behaviour of reconstituted soils at high initial water contents [texte imprimé] / Z.-S. Hong, Auteur ; J. Yin, Auteur ; Y.-J. Cui, Auteur . - 2011 . - pp. 691-700. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 9 (Septembre 2010) . - pp. 691-700 Mots-clés : Laboratory  equipment  Compressibility  Clays  Suction  pressure  Laboratory  tests Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Oedometer tests starting from a very small effective vertical stress of 0·5 kPa were performed on three reconstituted clays with different liquid limits. The soils were prepared at various initial water contents, ranging from 0·7 to 2·0 times their corresponding liquid limits. It is observed that the e–log σ ′ v compression curves show an inverse ‘S' shape due to suction pressure resisting deformation, similar to that of soft natural clays caused by consolidation yield stress. The suction pressure σ ′ s of the reconstituted clays can be correlated with the ratio of initial void ratio to void ratio at liquid limit e 0/e L. The suction pressure curve defined by a unique relationship between suction pressure σ ′ s and the normalised void ratio at suction pressure e s/e L is also proposed to distinguish between the pre-suction and the post-suction states. In addition, Burland's concept of the intrinsic compression line is adopted for correlating the compression curves of various reconstituted clays at high initial water contents. It has been found that the void index is a powerful parameter for normalising the compression curves in the post-suction state. Nevertheless, it seems that Burland's intrinsic compression line slightly underestimates the void index at the low stresses considered in this study. An extended intrinsic compression line is then derived in order to better fit the data for stresses lower than 25 kPa. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.09.p.059

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

Impact of initial state on the fabric and permeability of a lime-treated silt under long-term leaching / B. le Runigo in Canadian geotechnical journal, Vol. 46 N° 11 (Novembre 2009) 

Public ISBD [article]  in Canadian geotechnical journal > Vol. 46 N° 11 (Novembre 2009) . - pp. 1243–1257 Titre : Impact of initial state on the fabric and permeability of a lime-treated silt under long-term leaching Type de document : texte imprimé Auteurs : B. le Runigo, Auteur ; O. Cuisinier, Auteur ; Y.-J. Cui, Auteur Article en page(s) : pp. 1243–1257 Note générale : Sciences de la Terre Langues : Anglais (eng) Mots-clés : Lime-treated  silt  Permeability  Fabric  Initial  state  Leaching  Limon  traité  à  la  chaux  Perméabilité  Texture  Etat  initial  Lixiviation Index. décimale : 550 Sciences auxiliaires de la géologie. Résumé : The long-term performance of lime-treated soil is still in question, especially in the case of the use of such soils to build earthen structures in permanent contact with water (i.e., dams, river levees, etc.) Indeed, water circulation may induce significant alteration of the improvements brought by the lime treatment. In this context, the main objective of this work is to study the long-term behaviour (durability) of lime-treated soils submitted to water circulation as well as to determine the most favourable initial soil compaction in terms of lime-treated soil durability. First, the impact of lime addition on soil microstructure is investigated with mercury intrusion porosimetry tests. This was done to highlight the effect of curing time, lime dosage, and compaction on soil initial permeability, a critical parameter in terms of long-term behaviour of the lime-treated soil. Then, lime-treated soil samples were submitted to an accelerated circulation of water over a period of 150 days. The obtained results show that soil permeability did not fluctuate with circulation time. This has been confirmed by the results obtained on the samples’ microstructure that remained stable throughout the experiments. La performance à long terme des sols traités à la chaux est une question encore largement débattue, notamment dans le contexte de l’utilisation de ces sols pour la réalisation d’ouvrages en terre en contact permanent ou fréquent avec l’eau (digue, barrage, etc.). L’eau pourrait en effet induire une altération des améliorations apportées par le traitement à la chaux. Ce travail vise à apporter quelques éléments de réponse sur la durabilité des performances d’un sol traité à la chaux lorsqu’il est soumis à un écoulement d’eau avec un volet concernant l’identification des conditions de compactage du sol les plus favorables en terme de durabilité. Cette étude se consacre dans un premier temps à l’étude de l’ajout de chaux sur la microstructure du sol par l’utilisation de la porosimétrie au mercure. Cette étape était un préalable à une meilleure compréhension de l’impact du dosage, du temps de cure et des conditions de compactage sur la perméabilité du sol traité à la chaux. Dans un deuxième temps, le sol traité a été soumis à une circulation accélérée d’eau sur une période de 150 jours. Les résultats montrent que, dans le cas du limon étudié, la perméabilité du matériau n’évolue pas en cours de circulation, ce qui est à relier par la relative stabilité de la microstructure dans le cas du limon étudié. DEWEY : 550 ISSN : 0008-3674 En ligne : http://rparticle.web-p.cisti.nrc.ca/rparticle/AbstractTemplateServlet?calyLang=f [...] [article] Impact of initial state on the fabric and permeability of a lime-treated silt under long-term leaching [texte imprimé] / B. le Runigo, Auteur ; O. Cuisinier, Auteur ; Y.-J. Cui, Auteur . - pp. 1243–1257. Sciences de la Terre Langues : Anglais (eng) in Canadian geotechnical journal > Vol. 46 N° 11 (Novembre 2009) . - pp. 1243–1257 Mots-clés : Lime-treated  silt  Permeability  Fabric  Initial  state  Leaching  Limon  traité  à  la  chaux  Perméabilité  Texture  Etat  initial  Lixiviation Index. décimale : 550 Sciences auxiliaires de la géologie. Résumé : The long-term performance of lime-treated soil is still in question, especially in the case of the use of such soils to build earthen structures in permanent contact with water (i.e., dams, river levees, etc.) Indeed, water circulation may induce significant alteration of the improvements brought by the lime treatment. In this context, the main objective of this work is to study the long-term behaviour (durability) of lime-treated soils submitted to water circulation as well as to determine the most favourable initial soil compaction in terms of lime-treated soil durability. First, the impact of lime addition on soil microstructure is investigated with mercury intrusion porosimetry tests. This was done to highlight the effect of curing time, lime dosage, and compaction on soil initial permeability, a critical parameter in terms of long-term behaviour of the lime-treated soil. Then, lime-treated soil samples were submitted to an accelerated circulation of water over a period of 150 days. The obtained results show that soil permeability did not fluctuate with circulation time. This has been confirmed by the results obtained on the samples’ microstructure that remained stable throughout the experiments. La performance à long terme des sols traités à la chaux est une question encore largement débattue, notamment dans le contexte de l’utilisation de ces sols pour la réalisation d’ouvrages en terre en contact permanent ou fréquent avec l’eau (digue, barrage, etc.). L’eau pourrait en effet induire une altération des améliorations apportées par le traitement à la chaux. Ce travail vise à apporter quelques éléments de réponse sur la durabilité des performances d’un sol traité à la chaux lorsqu’il est soumis à un écoulement d’eau avec un volet concernant l’identification des conditions de compactage du sol les plus favorables en terme de durabilité. Cette étude se consacre dans un premier temps à l’étude de l’ajout de chaux sur la microstructure du sol par l’utilisation de la porosimétrie au mercure. Cette étape était un préalable à une meilleure compréhension de l’impact du dosage, du temps de cure et des conditions de compactage sur la perméabilité du sol traité à la chaux. Dans un deuxième temps, le sol traité a été soumis à une circulation accélérée d’eau sur une période de 150 jours. Les résultats montrent que, dans le cas du limon étudié, la perméabilité du matériau n’évolue pas en cours de circulation, ce qui est à relier par la relative stabilité de la microstructure dans le cas du limon étudié. DEWEY : 550 ISSN : 0008-3674 En ligne : http://rparticle.web-p.cisti.nrc.ca/rparticle/AbstractTemplateServlet?calyLang=f [...]

Yielding and plastic behaviour of Boom clay / N. Sultan in Géotechnique, Vol. 60 N° 9 (Septembre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 9 (Septembre 2010) . - pp. 657–666 Titre : Yielding and plastic behaviour of Boom clay Type de document : texte imprimé Auteurs : N. Sultan, Auteur ; Y.-J. Cui, Auteur ; P. Delage, Auteur Année de publication : 2011 Article en page(s) : pp. 657–666 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Laboratory  tests  Plasticity  Clays  Anisotropy  Elasticity  Constitutive  relations  Shear  strength Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : An underground research laboratory (URL) has been excavated in a deposit of Boom clay at a depth of 223 m by the SCK-CEN Belgian organisation near the city of Mol. This URL is devoted to research into nuclear waste disposal. This paper presents the results of an investigation carried out in the triaxial apparatus on specimens that were trimmed from blocks extracted during excavation sequences in the URL. In order to characterise the mechanical behaviour of the natural Boom clay and to examine the effect of initial and induced anisotropy on its constitutive behaviour, two series of triaxial tests were carried out. Special attention was devoted to the yield behaviour and the effects of stress history. Experimental results showed a clear relation between the shape of yield curves and stress history. The yield curve of the clay in its initial state was oriented along the K 0 line, illustrating the anisotropy of fabric that was generated during the soil deposition. Subsequent isotropic compression (up to 9 MPa) made the yield curve more and more oriented along the p′ axis. Based on these experimental results, an elasto-plastic model accounting for isotropic and anisotropic hardening in (p′:q) space was developed. The initial yield curve of the soil was taken inclined with respect to the p′ axis. The formulation proposed describes the change in shape, size and orientation of the yield curve, according to the stress history. Eight constitutive parameters were used to describe the anisotropic behaviour of the soil. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00142 [article] Yielding and plastic behaviour of Boom clay [texte imprimé] / N. Sultan, Auteur ; Y.-J. Cui, Auteur ; P. Delage, Auteur . - 2011 . - pp. 657–666. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 9 (Septembre 2010) . - pp. 657–666 Mots-clés : Laboratory  tests  Plasticity  Clays  Anisotropy  Elasticity  Constitutive  relations  Shear  strength Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : An underground research laboratory (URL) has been excavated in a deposit of Boom clay at a depth of 223 m by the SCK-CEN Belgian organisation near the city of Mol. This URL is devoted to research into nuclear waste disposal. This paper presents the results of an investigation carried out in the triaxial apparatus on specimens that were trimmed from blocks extracted during excavation sequences in the URL. In order to characterise the mechanical behaviour of the natural Boom clay and to examine the effect of initial and induced anisotropy on its constitutive behaviour, two series of triaxial tests were carried out. Special attention was devoted to the yield behaviour and the effects of stress history. Experimental results showed a clear relation between the shape of yield curves and stress history. The yield curve of the clay in its initial state was oriented along the K 0 line, illustrating the anisotropy of fabric that was generated during the soil deposition. Subsequent isotropic compression (up to 9 MPa) made the yield curve more and more oriented along the p′ axis. Based on these experimental results, an elasto-plastic model accounting for isotropic and anisotropic hardening in (p′:q) space was developed. The initial yield curve of the soil was taken inclined with respect to the p′ axis. The formulation proposed describes the change in shape, size and orientation of the yield curve, according to the stress history. Eight constitutive parameters were used to describe the anisotropic behaviour of the soil. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00142