Dépouillements

Embedded cantilever retaining walls in sand / A. Z. Li in Géotechnique, Vol. 60 N° 11 (Novembre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 11 (Novembre 2010) . - pp. 813–823 Titre : Embedded cantilever retaining walls in sand Type de document : texte imprimé Auteurs : A. Z. Li, Auteur ; B. M. Lehane, Auteur Année de publication : 2011 Article en page(s) : pp. 813–823 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Sands  Sands  Case  history  Retaining  walls Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper describes a case history involving staged excavation adjacent to an instrumented cantilever bored pile contiguous wall in sand. The instrumentation enabled reliable estimates to be made of the variation of pile bending moments from which observations are made related to the development of lateral earth pressures. Particle image velocimetry was employed to obtain a unique dataset of lateral and vertical displacement measurements behind the wall, which may be used to evaluate existing predictive approaches for assessment of excavation-induced movements. Simple finite-element back-analyses of the experiment, employing a linear elastic Mohr–Coulomb soil model, showed that measured wall displacements and moments could be predicted using expected effective stress strength parameters, but that best-fit equivalent linear operational stiffnesses were well below those commonly assumed in practice. Creep is shown to have a critical effect on the displacements of the wall and behind the wall and needs to be incorporated in any realistic predictive approach. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.147 [article] Embedded cantilever retaining walls in sand [texte imprimé] / A. Z. Li, Auteur ; B. M. Lehane, Auteur . - 2011 . - pp. 813–823. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 11 (Novembre 2010) . - pp. 813–823 Mots-clés : Sands  Sands  Case  history  Retaining  walls Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper describes a case history involving staged excavation adjacent to an instrumented cantilever bored pile contiguous wall in sand. The instrumentation enabled reliable estimates to be made of the variation of pile bending moments from which observations are made related to the development of lateral earth pressures. Particle image velocimetry was employed to obtain a unique dataset of lateral and vertical displacement measurements behind the wall, which may be used to evaluate existing predictive approaches for assessment of excavation-induced movements. Simple finite-element back-analyses of the experiment, employing a linear elastic Mohr–Coulomb soil model, showed that measured wall displacements and moments could be predicted using expected effective stress strength parameters, but that best-fit equivalent linear operational stiffnesses were well below those commonly assumed in practice. Creep is shown to have a critical effect on the displacements of the wall and behind the wall and needs to be incorporated in any realistic predictive approach. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.147

Centrifuge model study of spudcan penetration in sand overlying clay / K. L. Teh in Géotechnique, Vol. 60 N° 11 (Novembre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 11 (Novembre 2010) . - pp. 825–842 Titre : Centrifuge model study of spudcan penetration in sand overlying clay Type de document : texte imprimé Auteurs : K. L. Teh, Auteur ; C. F. Leung, Auteur ; Y. K. Chow, Auteur Année de publication : 2011 Article en page(s) : pp. 825–842 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Bearing  capacity  Sands  Footings/foundations  Centrifuge  modelling  Clays  Offshore  engineering Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : A series of centrifuge model tests has been conducted to investigate the bearing resistance of spudcan foundations of offshore jack-up rigs in sand overlying normally consolidated clay. The spudcan bearing-resistance profiles measured in most of the tests recorded a peak resistance at a shallow depth within the upper sand layer, followed by an abrupt post-peak reduction in resistance causing the spudcan to plunge into the underlying soft clay. This phenomenon is commonly termed as ‘spudcan punch-through hazard', which potentially leads to severe structural damage of jack-up rigs in the field. The centrifuge test results revealed that the ratio of upper sand layer thickness over spudcan diameter and the ratio of bearing resistance between the upper sand and underlying clay affect the development of spudcan bearing resistance. The limitations of existing design methods, which were derived for the ultimate bearing capacity of pre-embedded shallow foundation to assess the spudcan bearing resistance-depth profile, are also identified. It is proposed that the profile may be assessed by focusing on three key characteristic bearing resistances. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.077 [article] Centrifuge model study of spudcan penetration in sand overlying clay [texte imprimé] / K. L. Teh, Auteur ; C. F. Leung, Auteur ; Y. K. Chow, Auteur . - 2011 . - pp. 825–842. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 11 (Novembre 2010) . - pp. 825–842 Mots-clés : Bearing  capacity  Sands  Footings/foundations  Centrifuge  modelling  Clays  Offshore  engineering Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : A series of centrifuge model tests has been conducted to investigate the bearing resistance of spudcan foundations of offshore jack-up rigs in sand overlying normally consolidated clay. The spudcan bearing-resistance profiles measured in most of the tests recorded a peak resistance at a shallow depth within the upper sand layer, followed by an abrupt post-peak reduction in resistance causing the spudcan to plunge into the underlying soft clay. This phenomenon is commonly termed as ‘spudcan punch-through hazard', which potentially leads to severe structural damage of jack-up rigs in the field. The centrifuge test results revealed that the ratio of upper sand layer thickness over spudcan diameter and the ratio of bearing resistance between the upper sand and underlying clay affect the development of spudcan bearing resistance. The limitations of existing design methods, which were derived for the ultimate bearing capacity of pre-embedded shallow foundation to assess the spudcan bearing resistance-depth profile, are also identified. It is proposed that the profile may be assessed by focusing on three key characteristic bearing resistances. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.077

Estimation of intact and remoulded undrained shear strengths from penetration tests in soft clays / H. E. Low in Géotechnique, Vol. 60 N° 11 (Novembre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 11 (Novembre 2010) . - pp. 843–859 Titre : Estimation of intact and remoulded undrained shear strengths from penetration tests in soft clays Type de document : texte imprimé Auteurs : H. E. Low, Auteur ; T. Lunne, Auteur ; K. H. Andersen, Auteur Année de publication : 2011 Article en page(s) : pp. 843–859 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Shear  strength  in  situ  testing  Clays Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Difficulties in obtaining high-quality soil samples from deepwater sites have necessitated increasing reliance on piezocone, T-bar and ball penetration tests to determine soil properties for design purposes. This paper reports the results of an international collaborative project in which a worldwide high-quality database of lightly overconsolidated clays was assembled and used to evaluate resistance factors for the estimation of intact and remoulded undrained shear strength from the penetration resistance of each device. The derived factors were then compared with existing theoretical solutions to evaluate the influence of particular soil characteristics. The overall statistics showed similar levels of variability of the resistance factors, with low coefficients of variation, for all three types of penetrometer. However, correlations of the resistance factors with specific soil characteristics indicated that the resistance factors for the piezocone were more influenced by soil stiffness, or rigidity index, than for the T-bar and ball, while the effect of strength anisotropy was only apparent in respect of resistance factors for the T-bar and ball relative to shear strengths measured in triaxial compression. In the correlation between the remoulded penetration resistance and remoulded strength, the resistance factors for remoulded strength were found to be higher than those for intact strength and with a slight tendency to increase with increasing strength sensitivity but insensitive to soil index properties. Based on an assessment of the influence of various soil characteristics, resistance factors are recommended for the estimation of intact and remoulded undrained shear strength from the penetration resistances of each device for soil with strength sensitivity less than six. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.017 [article] Estimation of intact and remoulded undrained shear strengths from penetration tests in soft clays [texte imprimé] / H. E. Low, Auteur ; T. Lunne, Auteur ; K. H. Andersen, Auteur . - 2011 . - pp. 843–859. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 11 (Novembre 2010) . - pp. 843–859 Mots-clés : Shear  strength  in  situ  testing  Clays Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Difficulties in obtaining high-quality soil samples from deepwater sites have necessitated increasing reliance on piezocone, T-bar and ball penetration tests to determine soil properties for design purposes. This paper reports the results of an international collaborative project in which a worldwide high-quality database of lightly overconsolidated clays was assembled and used to evaluate resistance factors for the estimation of intact and remoulded undrained shear strength from the penetration resistance of each device. The derived factors were then compared with existing theoretical solutions to evaluate the influence of particular soil characteristics. The overall statistics showed similar levels of variability of the resistance factors, with low coefficients of variation, for all three types of penetrometer. However, correlations of the resistance factors with specific soil characteristics indicated that the resistance factors for the piezocone were more influenced by soil stiffness, or rigidity index, than for the T-bar and ball, while the effect of strength anisotropy was only apparent in respect of resistance factors for the T-bar and ball relative to shear strengths measured in triaxial compression. In the correlation between the remoulded penetration resistance and remoulded strength, the resistance factors for remoulded strength were found to be higher than those for intact strength and with a slight tendency to increase with increasing strength sensitivity but insensitive to soil index properties. Based on an assessment of the influence of various soil characteristics, resistance factors are recommended for the estimation of intact and remoulded undrained shear strength from the penetration resistances of each device for soil with strength sensitivity less than six. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.017

Reliability of CPT Ic as an index for mechanical behaviour classification of soils / C. S. Ku in Géotechnique, Vol. 60 N° 11 (Novembre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 11 (Novembre 2010) . - pp. 861–875 Titre : Reliability of CPT Ic as an index for mechanical behaviour classification of soils Type de document : texte imprimé Auteurs : C. S. Ku, Auteur ; C. H. Juang, Auteur ; C. Y. Ou, Auteur Année de publication : 2011 Article en page(s) : pp. 861–875 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Soil  classification  Liquefaction  Case  history  Statistical  analysis  In  situ  testing Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper presents results of an analysis of a set of high-quality, side-by-side piezocone penetration test (CPTu) and standard penetration test (SPT) data for examining mechanical behaviour-based classification of soils. The results show that the soil behaviour type index (I c), either defined by Jefferies and Been (denoted herein as I c,BJ) or by Robertson and Wride (denoted herein as I c,RW), is an effective parameter for mechanical behaviour classification. Additionally, an effort is made to find the most suitable I c cut-off (or boundary) value that can delineate cohesionless (sand-like) soils from cohesive (clay-like) soils. The Robertson and Wride's formulation, I c,RW = 2·67 is found capable of delineating these two classes of soils. Similarly for the Been and Jefferies' formulation, I c,BJ = 2·58 is found to be the most suitable I c cut-off value for such classification purpose. These cut-off I c values for distinguishing sand-like soils from clay-like soils are found to be reliable in a case study of liquefaction susceptibility. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.09.p.097 [article] Reliability of CPT Ic as an index for mechanical behaviour classification of soils [texte imprimé] / C. S. Ku, Auteur ; C. H. Juang, Auteur ; C. Y. Ou, Auteur . - 2011 . - pp. 861–875. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 11 (Novembre 2010) . - pp. 861–875 Mots-clés : Soil  classification  Liquefaction  Case  history  Statistical  analysis  In  situ  testing Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper presents results of an analysis of a set of high-quality, side-by-side piezocone penetration test (CPTu) and standard penetration test (SPT) data for examining mechanical behaviour-based classification of soils. The results show that the soil behaviour type index (I c), either defined by Jefferies and Been (denoted herein as I c,BJ) or by Robertson and Wride (denoted herein as I c,RW), is an effective parameter for mechanical behaviour classification. Additionally, an effort is made to find the most suitable I c cut-off (or boundary) value that can delineate cohesionless (sand-like) soils from cohesive (clay-like) soils. The Robertson and Wride's formulation, I c,RW = 2·67 is found capable of delineating these two classes of soils. Similarly for the Been and Jefferies' formulation, I c,BJ = 2·58 is found to be the most suitable I c cut-off value for such classification purpose. These cut-off I c values for distinguishing sand-like soils from clay-like soils are found to be reliable in a case study of liquefaction susceptibility. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.09.p.097

Consolidation in accreting sediments: Gibson's solution applied to backfilling of mine stopes / M. Fahey in Géotechnique, Vol. 60 N° 11 (Novembre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 11 (Novembre 2010) . - pp. 877–882 Titre : Consolidation in accreting sediments: Gibson's solution applied to backfilling of mine stopes Type de document : texte imprimé Auteurs : M. Fahey, Auteur ; M. Helinski, Auteur ; A. Fourie, Auteur Année de publication : 2011 Article en page(s) : pp. 877–882 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Consolidation  Mining Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : There is increasing use of hydraulically placed tailings backfill in mined-out voids (‘stopes') in underground mining, with the backfill being retained in the stopes by barricades built across the stope access tunnels. The forces acting on these barricades depend on the degree of consolidation that occurs during the backfilling process. A solution to the problem of consolidation in a layer increasing in thickness owing to ongoing sedimentation was proposed by Gibson in 1958. This solution appears to be directly relevant to the stope backfilling process, although there are limitations in applying it. Using material properties from two mine sites, the applicability of the Gibson solution to stope filling is examined. In particular, since one of the basic assumptions of the Gibson solution (that c v remains constant during filling) is generally violated, the effect of having a varying c v is explored using numerical modelling. Finally, the limitations of applying the Gibson solution to the stope backfilling problem are discussed. These relate particularly to the three-dimensional nature of stope geometry and drainage (compared with the assumption of one-dimensional conditions in the Gibson solution) and the fact that cement is generally added to backfill, such that the analysis herein is only valid up to the start of cement hydration. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.078 [article] Consolidation in accreting sediments: Gibson's solution applied to backfilling of mine stopes [texte imprimé] / M. Fahey, Auteur ; M. Helinski, Auteur ; A. Fourie, Auteur . - 2011 . - pp. 877–882. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 11 (Novembre 2010) . - pp. 877–882 Mots-clés : Consolidation  Mining Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : There is increasing use of hydraulically placed tailings backfill in mined-out voids (‘stopes') in underground mining, with the backfill being retained in the stopes by barricades built across the stope access tunnels. The forces acting on these barricades depend on the degree of consolidation that occurs during the backfilling process. A solution to the problem of consolidation in a layer increasing in thickness owing to ongoing sedimentation was proposed by Gibson in 1958. This solution appears to be directly relevant to the stope backfilling process, although there are limitations in applying it. Using material properties from two mine sites, the applicability of the Gibson solution to stope filling is examined. In particular, since one of the basic assumptions of the Gibson solution (that c v remains constant during filling) is generally violated, the effect of having a varying c v is explored using numerical modelling. Finally, the limitations of applying the Gibson solution to the stope backfilling problem are discussed. These relate particularly to the three-dimensional nature of stope geometry and drainage (compared with the assumption of one-dimensional conditions in the Gibson solution) and the fact that cement is generally added to backfill, such that the analysis herein is only valid up to the start of cement hydration. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.078

Assessment of sample quality in soft clay using shear wave velocity and suction measurements / S. Donohue in Géotechnique, Vol. 60 N° 11 (Novembre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 11 (Novembre 2010) . - pp. 883–889 Titre : Assessment of sample quality in soft clay using shear wave velocity and suction measurements Type de document : texte imprimé Auteurs : S. Donohue, Auteur ; M. Long, Auteur Année de publication : 2011 Article en page(s) : pp. 883–889 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : In  situ  testing  Waves  and  wave  loading  Clays  Sampling  Laboratory  tests  Suction Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The characterisation of soils for civil engineering purposes depends on removing sufficiently high-quality samples from the ground. Accurate evaluation of sample quality is therefore important if reliable design parameters are to be determined. This paper describes the use of unconfined shear wave velocity (V s) and suction (u r) measurements to assess sample quality rapidly in soft clay. Samples of varying quality from three well-characterised soft clay sites are initially assessed using conventional techniques, and their results compared with V s and u r measurements performed on the same samples. It is observed that the quality of samples indicated by these measurements is very similar to those inferred from traditional disturbance measures, with V s being the more reliable indicator. A tentative empirically derived criterion, based on samples tested in this project, is proposed to quantify sample disturbance combining both V s and u r measurements. Further work using this criterion on different materials is important so as to test its usefulness. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.t.007.3741 [article] Assessment of sample quality in soft clay using shear wave velocity and suction measurements [texte imprimé] / S. Donohue, Auteur ; M. Long, Auteur . - 2011 . - pp. 883–889. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 11 (Novembre 2010) . - pp. 883–889 Mots-clés : In  situ  testing  Waves  and  wave  loading  Clays  Sampling  Laboratory  tests  Suction Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The characterisation of soils for civil engineering purposes depends on removing sufficiently high-quality samples from the ground. Accurate evaluation of sample quality is therefore important if reliable design parameters are to be determined. This paper describes the use of unconfined shear wave velocity (V s) and suction (u r) measurements to assess sample quality rapidly in soft clay. Samples of varying quality from three well-characterised soft clay sites are initially assessed using conventional techniques, and their results compared with V s and u r measurements performed on the same samples. It is observed that the quality of samples indicated by these measurements is very similar to those inferred from traditional disturbance measures, with V s being the more reliable indicator. A tentative empirically derived criterion, based on samples tested in this project, is proposed to quantify sample disturbance combining both V s and u r measurements. Further work using this criterion on different materials is important so as to test its usefulness. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.t.007.3741

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