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Comparison between models of rock discontinuity strength and deformation / D. A. F. Oliveira in Journal of geotechnical and geoenvironmental engineering, Vol. 136 N° 6 (Juin 2010) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 6 (Juin 2010) . - pp. 864-874 Titre : Comparison between models of rock discontinuity strength and deformation Type de document : texte imprimé Auteurs : D. A. F. Oliveira, Auteur ; B. Indraratna, Auteur Année de publication : 2010 Article en page(s) : pp. 864-874 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Rock  joint  models  Soil-infill  Shear-displacement  behavior  Numerical  modeling  Tunneling Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : One important component in the design of tunnels in urban areas is a correct assessment of the interaction between the underground excavation with other structures in the vicinity. In this sense a correct stress-strain response by the model representing the rock mass behavior is essential. The shear and normal displacement of rock discontinuities and their shear and normal stiffness control the distribution of stress and displacement within a discontinuous rock mass. In conditions where an equivalent continuum based approach is not applicable, the joint material model should be able to describe important mechanisms such as asperity sliding and shearing, post-peak behavior, asperity deformation, and the effect of soft infilling. The distinct element code UDEC was used to simulate the direct shear tests on a natural joint profile, and the prediction of two existing models of discontinuity strength and deformation were then compared with a new soil-infilled joint model and with experimental data for clean and soil-infilled rock joints. A numerical modeling of a cavern excavated in a jointed medium is also presented to illustrate the response of different models. The proposed soil-infilled joint model described more comprehensively the occurrence of dilation and compression with lateral displacements and also better represented the double peak shearing in relation to the adopted squeezing mechanism that could not be captured by the two existing models. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i6/p864_s1?isAuthorized=no [article] Comparison between models of rock discontinuity strength and deformation [texte imprimé] / D. A. F. Oliveira, Auteur ; B. Indraratna, Auteur . - 2010 . - pp. 864-874. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 6 (Juin 2010) . - pp. 864-874 Mots-clés : Rock  joint  models  Soil-infill  Shear-displacement  behavior  Numerical  modeling  Tunneling Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : One important component in the design of tunnels in urban areas is a correct assessment of the interaction between the underground excavation with other structures in the vicinity. In this sense a correct stress-strain response by the model representing the rock mass behavior is essential. The shear and normal displacement of rock discontinuities and their shear and normal stiffness control the distribution of stress and displacement within a discontinuous rock mass. In conditions where an equivalent continuum based approach is not applicable, the joint material model should be able to describe important mechanisms such as asperity sliding and shearing, post-peak behavior, asperity deformation, and the effect of soft infilling. The distinct element code UDEC was used to simulate the direct shear tests on a natural joint profile, and the prediction of two existing models of discontinuity strength and deformation were then compared with a new soil-infilled joint model and with experimental data for clean and soil-infilled rock joints. A numerical modeling of a cavern excavated in a jointed medium is also presented to illustrate the response of different models. The proposed soil-infilled joint model described more comprehensively the occurrence of dilation and compression with lateral displacements and also better represented the double peak shearing in relation to the adopted squeezing mechanism that could not be captured by the two existing models. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i6/p864_s1?isAuthorized=no

A shear-displacement criterion for soil-infilled rock discontinuities / B. Indraratna in Géotechnique, Vol. 60 N° 8 (Août 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 8 (Août 2010) . - pp. 623–633 Titre : A shear-displacement criterion for soil-infilled rock discontinuities Type de document : texte imprimé Auteurs : B. Indraratna, Auteur ; D. A. F. Oliveira, Auteur ; E. T. Brown, Auteur Année de publication : 2011 Article en page(s) : pp. 623–633 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Shear  strength  Clays  Laboratory  tests  Rocks/rock  mechanics Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : An infilled rock joint is likely to be the weakest plane in a rock mass. The most pronounced effect of the presence of infill material is the reduction in friction of the discontinuity boundaries (i.e. rock to rock contact of the joint walls). The thicker the infill, the smaller the shear strength of the rock joint. Once the infill reaches a critical thickness, the joint walls (rock) play no significant role in the overall shear strength. Several models have been proposed to predict the peak shear strength of infilled joints under both constant normal load and constant normal stiffness boundary conditions, taking into account the ratio of infill thickness (t) to the height of the joint wall asperity (a), that is the t/a ratio. Models based on the constant normal stiffness condition provide a much more accurate representation of the infilled joint behaviour in the field, but only a limited number of studies have focused on the more realistic constant normal stiffness stress–strain behaviour. This paper presents a critical review of some of the earlier studies and the most recent advancement of a shear-strength model developed at University of Wollongong, Australia, supplemented with laboratory data for model validation. The effect of different factors on the shear behaviour such as the t/a ratio, infill friction angle, joint wall roughness, joint stiffness and type of infill are presented. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.094 [article] A shear-displacement criterion for soil-infilled rock discontinuities [texte imprimé] / B. Indraratna, Auteur ; D. A. F. Oliveira, Auteur ; E. T. Brown, Auteur . - 2011 . - pp. 623–633. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 8 (Août 2010) . - pp. 623–633 Mots-clés : Shear  strength  Clays  Laboratory  tests  Rocks/rock  mechanics Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : An infilled rock joint is likely to be the weakest plane in a rock mass. The most pronounced effect of the presence of infill material is the reduction in friction of the discontinuity boundaries (i.e. rock to rock contact of the joint walls). The thicker the infill, the smaller the shear strength of the rock joint. Once the infill reaches a critical thickness, the joint walls (rock) play no significant role in the overall shear strength. Several models have been proposed to predict the peak shear strength of infilled joints under both constant normal load and constant normal stiffness boundary conditions, taking into account the ratio of infill thickness (t) to the height of the joint wall asperity (a), that is the t/a ratio. Models based on the constant normal stiffness condition provide a much more accurate representation of the infilled joint behaviour in the field, but only a limited number of studies have focused on the more realistic constant normal stiffness stress–strain behaviour. This paper presents a critical review of some of the earlier studies and the most recent advancement of a shear-strength model developed at University of Wollongong, Australia, supplemented with laboratory data for model validation. The effect of different factors on the shear behaviour such as the t/a ratio, infill friction angle, joint wall roughness, joint stiffness and type of infill are presented. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.094

The use of particle size distribution by surface area method in predicting the saturated hydraulic conductivity of graded granular soils / L. D. O. Trani in Géotechnique, Vol. 60 N° 12 (Décembre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 12 (Décembre 2010) . - pp. 957–962 Titre : The use of particle size distribution by surface area method in predicting the saturated hydraulic conductivity of graded granular soils Type de document : texte imprimé Auteurs : L. D. O. Trani, Auteur ; B. Indraratna, Auteur Année de publication : 2011 Article en page(s) : pp. 957–962 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Laboratory  tests  Filters  Seepage  Permeability  Gravels  Sands Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The hydraulic conductivity (k) of a fully saturated granular material can be predicted by the well-known Kozeny–Carman formula, and its slightly different variations, based on the porosity (n) and effective diameter (d eff). Most variations of the Kozeny–Carman formula compute the parameter d eff based on a given conventional particle size distribution by mass (PSDm), where the validation would normally be carried out by comparing against laboratory permeability tests conducted on soils having an average coefficient of uniformity (C u) of about 3. Knowing that the Kozeny–Carman formula was originally developed for uniformly graded materials, inevitable limitations are inherited when it is applied to increasingly graded soils. This study proposes to convert the PSDm into its equivalence in surface area (PSDsa) conforming to the fundamental geometric assumption by which the Kozeny–Carman equation was originally formulated. The estimated d eff based on this proposed PSDsa method appears implicitly to incorporate the size, shape and angularity of the natural grains which were traditionally represented by the shape coefficient ( α ). The results presented in this paper show that the suggested method is capable of predicting k for fully saturated granular soils with C u of up 20. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.t.014 [article] The use of particle size distribution by surface area method in predicting the saturated hydraulic conductivity of graded granular soils [texte imprimé] / L. D. O. Trani, Auteur ; B. Indraratna, Auteur . - 2011 . - pp. 957–962. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 12 (Décembre 2010) . - pp. 957–962 Mots-clés : Laboratory  tests  Filters  Seepage  Permeability  Gravels  Sands Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The hydraulic conductivity (k) of a fully saturated granular material can be predicted by the well-known Kozeny–Carman formula, and its slightly different variations, based on the porosity (n) and effective diameter (d eff). Most variations of the Kozeny–Carman formula compute the parameter d eff based on a given conventional particle size distribution by mass (PSDm), where the validation would normally be carried out by comparing against laboratory permeability tests conducted on soils having an average coefficient of uniformity (C u) of about 3. Knowing that the Kozeny–Carman formula was originally developed for uniformly graded materials, inevitable limitations are inherited when it is applied to increasingly graded soils. This study proposes to convert the PSDm into its equivalence in surface area (PSDsa) conforming to the fundamental geometric assumption by which the Kozeny–Carman equation was originally formulated. The estimated d eff based on this proposed PSDsa method appears implicitly to incorporate the size, shape and angularity of the natural grains which were traditionally represented by the shape coefficient ( α ). The results presented in this paper show that the suggested method is capable of predicting k for fully saturated granular soils with C u of up 20. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.t.014

Vertical drain consolidation with non-Darcian flow and void-ratio-dependent compressibility and permeability / R. Walker in Géotechnique, Vol. 62 N° 11 (Novembre 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 11 (Novembre 2012) . - pp. 985 –997 Titre : Vertical drain consolidation with non-Darcian flow and void-ratio-dependent compressibility and permeability Type de document : texte imprimé Auteurs : R. Walker, Auteur ; B. Indraratna, Auteur ; C. Rujikiatkamjorn, Auteur Année de publication : 2012 Article en page(s) : pp. 985 –997 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Consolidation  Case  history  Pore  pressures  Settlement Résumé : Vertical drains increase the rate of consolidation in soft soils by facilitating faster dissipation of excess pore water pressure through short, horizontal drainage paths. This paper presents an analytical solution for non-linear radial consolidation under equal-strain conditions incorporating smear but ignoring well resistance. Three aspects of non-linearity are considered: (a) non-Darcian flow, (b) a log-linear void-ratio–stress relationship; and (b) a log-linear void-ratio–permeability relationship. The analytical solution to non-linear radial consolidation can explicitly capture the behaviour of both overconsolidated and normally consolidated soils. For non-linear material properties, consolidation may be faster or slower when compared with the cases with constant material properties. The difference depends on the compressibility/permeability ratios (C c/C k and C r/C k), the preconsolidation pressure and the stress increase. If C c/C k < 1 or C r/C k < 1 then the coefficient of consolidation increases as excess pore pressures dissipate, and the corresponding rate of consolidation is greater. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.084 [article] Vertical drain consolidation with non-Darcian flow and void-ratio-dependent compressibility and permeability [texte imprimé] / R. Walker, Auteur ; B. Indraratna, Auteur ; C. Rujikiatkamjorn, Auteur . - 2012 . - pp. 985 –997. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 11 (Novembre 2012) . - pp. 985 –997 Mots-clés : Consolidation  Case  history  Pore  pressures  Settlement Résumé : Vertical drains increase the rate of consolidation in soft soils by facilitating faster dissipation of excess pore water pressure through short, horizontal drainage paths. This paper presents an analytical solution for non-linear radial consolidation under equal-strain conditions incorporating smear but ignoring well resistance. Three aspects of non-linearity are considered: (a) non-Darcian flow, (b) a log-linear void-ratio–stress relationship; and (b) a log-linear void-ratio–permeability relationship. The analytical solution to non-linear radial consolidation can explicitly capture the behaviour of both overconsolidated and normally consolidated soils. For non-linear material properties, consolidation may be faster or slower when compared with the cases with constant material properties. The difference depends on the compressibility/permeability ratios (C c/C k and C r/C k), the preconsolidation pressure and the stress increase. If C c/C k < 1 or C r/C k < 1 then the coefficient of consolidation increases as excess pore pressures dissipate, and the corresponding rate of consolidation is greater. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.084