Dépouillements

Spatial variability of in situ weathered soil / S. M. Dasaka in Géotechnique, Vol. 62 N° 5 (Mai 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 375 –384 Titre : Spatial variability of in situ weathered soil Type de document : texte imprimé Auteurs : S. M. Dasaka, Auteur ; Zhang, L. M., Auteur Année de publication : 2012 Article en page(s) : pp. 375 –384 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Sampling  Piles  Site  investigation  Statistical  analysis  Geology  Residual  soils Résumé : The founding depths of pile foundations depend primarily on the loading conditions of the superstructure and the strength of subsoil. The depth of Grade III weathered rock, the top of completely decomposed granite (CDG), and standard penetration test N-value of 200 (SPT-200) are often used as indicators for decision-making in arriving at the preliminary founding depth of piles in Hong Kong. The work reported in this paper focuses on evaluation of the spatial variability characteristics of the above founding depth indicators at a construction site, using statistical models based on random field theory. Spatial variability characteristics are evaluated using the measured data in terms of scale of fluctuation. Geostatistics is used to obtain additional data at unsampled locations for mapping profiles of founding depth indicators over the site, using the measured data from borehole records and site investigation results. It is observed from the results that, if faults are not present, the depth of the Grade III surface exhibits the largest scale of fluctuation among the three indicators, and the variability of the ground is observed to increase with the weathering grade. The effect of the size of the sampling domain on the autocorrelation characteristics of the founding depth indicators is also studied. The results demonstrate that the scale of fluctuation increases with increase in the size of the sampling domain. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.P.151.3786 [article] Spatial variability of in situ weathered soil [texte imprimé] / S. M. Dasaka, Auteur ; Zhang, L. M., Auteur . - 2012 . - pp. 375 –384. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 375 –384 Mots-clés : Sampling  Piles  Site  investigation  Statistical  analysis  Geology  Residual  soils Résumé : The founding depths of pile foundations depend primarily on the loading conditions of the superstructure and the strength of subsoil. The depth of Grade III weathered rock, the top of completely decomposed granite (CDG), and standard penetration test N-value of 200 (SPT-200) are often used as indicators for decision-making in arriving at the preliminary founding depth of piles in Hong Kong. The work reported in this paper focuses on evaluation of the spatial variability characteristics of the above founding depth indicators at a construction site, using statistical models based on random field theory. Spatial variability characteristics are evaluated using the measured data in terms of scale of fluctuation. Geostatistics is used to obtain additional data at unsampled locations for mapping profiles of founding depth indicators over the site, using the measured data from borehole records and site investigation results. It is observed from the results that, if faults are not present, the depth of the Grade III surface exhibits the largest scale of fluctuation among the three indicators, and the variability of the ground is observed to increase with the weathering grade. The effect of the size of the sampling domain on the autocorrelation characteristics of the founding depth indicators is also studied. The results demonstrate that the scale of fluctuation increases with increase in the size of the sampling domain. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.P.151.3786

Tunnels in sands / A. M. Marshall in Géotechnique, Vol. 62 N° 5 (Mai 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 385 –399 Titre : Tunnels in sands : The effect of size, depth and volume loss on greenfield displacements Type de document : texte imprimé Auteurs : A. M. Marshall, Auteur ; R. Farrell, Auteur ; A. Klar, Auteur Année de publication : 2012 Article en page(s) : pp. 385 –399 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Tunnels  Settlement  Centrifuge  modelling  Sands Résumé : This paper examines the effect that tunnel size, depth and volume loss have on greenfield soil displacements above tunnels in sandy ground. The results of a series of plane-strain centrifuge tests performed on tunnels in a dry silica sand are examined. The cover-to-diameter ratio, C/D, of the tunnels ranged from 1·3 to 4·4. Features of greenfield settlement trough shape, both surface and subsurface, are illustrated by examining soil displacement data obtained using an image-based deformation measurement technique. The effects of tunnel size, depth and volume loss are demonstrated, and the suitability of typical fitting curves is discussed. The complex volumetric behaviour of drained soil is illustrated by comparing tunnel volume loss with the volume loss experienced by the soil. A set of equations is developed that provide a method of evaluating the change of settlement trough shape with tunnel size, depth and volume loss. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.047 [article] Tunnels in sands : The effect of size, depth and volume loss on greenfield displacements [texte imprimé] / A. M. Marshall, Auteur ; R. Farrell, Auteur ; A. Klar, Auteur . - 2012 . - pp. 385 –399. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 385 –399 Mots-clés : Tunnels  Settlement  Centrifuge  modelling  Sands Résumé : This paper examines the effect that tunnel size, depth and volume loss have on greenfield soil displacements above tunnels in sandy ground. The results of a series of plane-strain centrifuge tests performed on tunnels in a dry silica sand are examined. The cover-to-diameter ratio, C/D, of the tunnels ranged from 1·3 to 4·4. Features of greenfield settlement trough shape, both surface and subsurface, are illustrated by examining soil displacement data obtained using an image-based deformation measurement technique. The effects of tunnel size, depth and volume loss are demonstrated, and the suitability of typical fitting curves is discussed. The complex volumetric behaviour of drained soil is illustrated by comparing tunnel volume loss with the volume loss experienced by the soil. A set of equations is developed that provide a method of evaluating the change of settlement trough shape with tunnel size, depth and volume loss. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.047

Effect of time on spudcan–footprint interaction in clay / C.T. Gan in Géotechnique, Vol. 62 N° 5 (Mai 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 401 –413 Titre : Effect of time on spudcan–footprint interaction in clay Type de document : texte imprimé Auteurs : C.T. Gan, Auteur ; C. F. Leung, Auteur ; M. J. Cassidy, Auteur Année de publication : 2012 Article en page(s) : pp. 401 –413 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Centrifuge  modelling  Clays  Soil/structure  interaction  Foundations  Offshore  engineering Résumé : Mobile drilling platforms often return to sites where previous installation, operation and extraction have formed footprints on the seabed. Owing to soil consolidation during the jack-up operational period and the intervening period before reinstallation, the interaction between a new spudcan installation and an existing footprint is complex and time dependent. This paper presents a series of drum centrifuge model tests to investigate the changes in the shear strength of soils beneath and adjacent to a spudcan footprint in normally and overconsolidated clays. The changes with time after two different jack-up operational periods are presented. The results reveal that the soil beneath a footprint generally loses some strength initially, owing to soil remoulding, but it subsequently regains its strength with time as it reconsolidates. The soil remoulding and subsequent strength gain are found to be more significant in normally consolidated clay than in overconsolidated clay. A longer jack-up operational period has an effect of strengthening the underlying soil below the spudcan in both clays. The vertical load, induced horizontal load and moment on a spudcan during its reinstallation into an existing footprint at different times after footprint formation are studied. Compared with the load for installing a spudcan for the first time, the load required to reinstall the same spudcan to the same depth is smaller in normally consolidated clay if the elapsed time between footprint formation and spudcan reinstallation is relatively short. The required load for spudcan reinstallation subsequently increases with footprint elapsed time. For overconsolidated clay, the load required for spudcan reinstallation is always smaller than that for initial spudcan installation, irrespective of the time between installations. The effects of original in situ soil strength, changes in soil strength with time and footprint elapsed time on the interaction between spudcan and footprint are examined. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.063 [article] Effect of time on spudcan–footprint interaction in clay [texte imprimé] / C.T. Gan, Auteur ; C. F. Leung, Auteur ; M. J. Cassidy, Auteur . - 2012 . - pp. 401 –413. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 401 –413 Mots-clés : Centrifuge  modelling  Clays  Soil/structure  interaction  Foundations  Offshore  engineering Résumé : Mobile drilling platforms often return to sites where previous installation, operation and extraction have formed footprints on the seabed. Owing to soil consolidation during the jack-up operational period and the intervening period before reinstallation, the interaction between a new spudcan installation and an existing footprint is complex and time dependent. This paper presents a series of drum centrifuge model tests to investigate the changes in the shear strength of soils beneath and adjacent to a spudcan footprint in normally and overconsolidated clays. The changes with time after two different jack-up operational periods are presented. The results reveal that the soil beneath a footprint generally loses some strength initially, owing to soil remoulding, but it subsequently regains its strength with time as it reconsolidates. The soil remoulding and subsequent strength gain are found to be more significant in normally consolidated clay than in overconsolidated clay. A longer jack-up operational period has an effect of strengthening the underlying soil below the spudcan in both clays. The vertical load, induced horizontal load and moment on a spudcan during its reinstallation into an existing footprint at different times after footprint formation are studied. Compared with the load for installing a spudcan for the first time, the load required to reinstall the same spudcan to the same depth is smaller in normally consolidated clay if the elapsed time between footprint formation and spudcan reinstallation is relatively short. The required load for spudcan reinstallation subsequently increases with footprint elapsed time. For overconsolidated clay, the load required for spudcan reinstallation is always smaller than that for initial spudcan installation, irrespective of the time between installations. The effects of original in situ soil strength, changes in soil strength with time and footprint elapsed time on the interaction between spudcan and footprint are examined. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.063

Rockfill shear strength evaluation / E. Frossard in Géotechnique, Vol. 62 N° 5 (Mai 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 415 –427 Titre : Rockfill shear strength evaluation : A rational method based on size effects Type de document : texte imprimé Auteurs : E. Frossard, Auteur ; W. Hu, Auteur ; C. Dano, Auteur Année de publication : 2012 Article en page(s) : pp. 415 –427 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Dams  Particle  crushing/crushability  Shear  strength Résumé : The shear strength of coarse granular materials, widely used in civil works such as rockfill in dam construction, is seldom measured because of severe practical experimental limitations. This paper presents an original method for evaluating the shear strength of such materials, based on size effects in granular materials affected by grain breakage according to fracture mechanics. Through a general size effect relation operating on shear strength envelopes, this method makes it possible to determine the shear strength of a coarse-grained granular material from the measured properties of a finer-grained granular material made of the same mineral. In the paper, the method is explicitly proved, taking into account the statistical distribution of breakage resistances of particles with different sizes, within materials that can be considered as physically similar, particularly having parallel grain size distributions and the same compactness. A wide set of independent experimental results is shown to validate the method consistently. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.079 [article] Rockfill shear strength evaluation : A rational method based on size effects [texte imprimé] / E. Frossard, Auteur ; W. Hu, Auteur ; C. Dano, Auteur . - 2012 . - pp. 415 –427. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 415 –427 Mots-clés : Dams  Particle  crushing/crushability  Shear  strength Résumé : The shear strength of coarse granular materials, widely used in civil works such as rockfill in dam construction, is seldom measured because of severe practical experimental limitations. This paper presents an original method for evaluating the shear strength of such materials, based on size effects in granular materials affected by grain breakage according to fracture mechanics. Through a general size effect relation operating on shear strength envelopes, this method makes it possible to determine the shear strength of a coarse-grained granular material from the measured properties of a finer-grained granular material made of the same mineral. In the paper, the method is explicitly proved, taking into account the statistical distribution of breakage resistances of particles with different sizes, within materials that can be considered as physically similar, particularly having parallel grain size distributions and the same compactness. A wide set of independent experimental results is shown to validate the method consistently. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.079

Factors controlling the seasonal variation in soil water content and pore water pressures within a lightly vegetated clay slope / J.A. Smethurst in Géotechnique, Vol. 62 N° 5 (Mai 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 429 –446 Titre : Factors controlling the seasonal variation in soil water content and pore water pressures within a lightly vegetated clay slope Type de document : texte imprimé Auteurs : J.A. Smethurst, Auteur ; D. Clarke, Auteur ; W. Powrie, Auteur Année de publication : 2012 Article en page(s) : pp. 429 –446 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Suction  Slopes  Clays  Monitoring  Pore  pressures  Vegetation Résumé : Seasonal cycles of soil water content cause shrinking and swelling in clay soils, which can in turn contribute to strain-softening and progressive slope failure. This paper presents and analyses six years of field measurements of soil water content and pore water pressures in the upper layers of a lightly vegetated London Clay slope near Newbury, UK, and shows how they can be related quantitatively to the climate using a water balance model. The field observations are set in the context of a 40-year run of rainfall data for the site. Moderately extreme rainfall and drought events were experienced over the period 2003–2008, allowing almost the full variation in likely pore water pressures to be characterised. Pore water pressures were found to return to near hydrostatic during most winters. Variations in summer rainfall, particularly during June–August, are shown to have a large influence on the magnitude of the cycles of pore water pressure and effective stress. The 40-year rainfall dataset is used to calculate approximate return periods for the observed soil conditions, and provides a benchmark for calculating the impacts of expected climate change on similar sites. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.097 [article] Factors controlling the seasonal variation in soil water content and pore water pressures within a lightly vegetated clay slope [texte imprimé] / J.A. Smethurst, Auteur ; D. Clarke, Auteur ; W. Powrie, Auteur . - 2012 . - pp. 429 –446. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 429 –446 Mots-clés : Suction  Slopes  Clays  Monitoring  Pore  pressures  Vegetation Résumé : Seasonal cycles of soil water content cause shrinking and swelling in clay soils, which can in turn contribute to strain-softening and progressive slope failure. This paper presents and analyses six years of field measurements of soil water content and pore water pressures in the upper layers of a lightly vegetated London Clay slope near Newbury, UK, and shows how they can be related quantitatively to the climate using a water balance model. The field observations are set in the context of a 40-year run of rainfall data for the site. Moderately extreme rainfall and drought events were experienced over the period 2003–2008, allowing almost the full variation in likely pore water pressures to be characterised. Pore water pressures were found to return to near hydrostatic during most winters. Variations in summer rainfall, particularly during June–August, are shown to have a large influence on the magnitude of the cycles of pore water pressure and effective stress. The 40-year rainfall dataset is used to calculate approximate return periods for the observed soil conditions, and provides a benchmark for calculating the impacts of expected climate change on similar sites. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.097

Exact undrained elasto-plastic solution for cylindrical cavity expansion in modified Cam Clay soil / S. L. Chen in Géotechnique, Vol. 62 N° 5 (Mai 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 447 –456 Titre : Exact undrained elasto-plastic solution for cylindrical cavity expansion in modified Cam Clay soil Type de document : texte imprimé Auteurs : S. L. Chen, Auteur ; Y. N. Abousleiman, Auteur Année de publication : 2012 Article en page(s) : pp. 447 –456 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Theoretical  analysis  Pore  pressure  Stress  path  Plasticity  Stress  analysis  In  situ  testing Résumé : This paper presents an exact semi-analytical analysis for cylindrical cavity expansion in modified Cam Clay critical state soil under the undrained condition. By assuming small-strain deformation in the elastic region and large-strain deformation in the plastic region, the formulation of the problem is reduced to solving a system of first-order ordinary differential equations for the radial, tangential and vertical effective stresses in the plastic zone. The pore pressure distribution can subsequently be determined from the radial equilibrium equation in terms of the total stresses. The semi-analytical solution derived in this paper follows the rigorous definitions for the two effective stress invariants instead of approximate ones, as usually assumed in the existing literature, and applies to the more general case where the out-of-plane (vertical) in situ stress may be different from the in-plane (horizontal) one. The results show clearly that the stress history (overconsolidation ratio) has a significant influence on the stress and pore pressure distributions around the cavity. The present solution provides an exact and realistic theoretical framework for predicting the soil behaviour around the cylindrical cavity, with applications to the interpretation of pressuremeter tests and to pile installation problems. It also serves as a valuable benchmark for verifying various cavity expansion numerical methods involving the critical state plasticity model. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.P.027 [article] Exact undrained elasto-plastic solution for cylindrical cavity expansion in modified Cam Clay soil [texte imprimé] / S. L. Chen, Auteur ; Y. N. Abousleiman, Auteur . - 2012 . - pp. 447 –456. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 447 –456 Mots-clés : Theoretical  analysis  Pore  pressure  Stress  path  Plasticity  Stress  analysis  In  situ  testing Résumé : This paper presents an exact semi-analytical analysis for cylindrical cavity expansion in modified Cam Clay critical state soil under the undrained condition. By assuming small-strain deformation in the elastic region and large-strain deformation in the plastic region, the formulation of the problem is reduced to solving a system of first-order ordinary differential equations for the radial, tangential and vertical effective stresses in the plastic zone. The pore pressure distribution can subsequently be determined from the radial equilibrium equation in terms of the total stresses. The semi-analytical solution derived in this paper follows the rigorous definitions for the two effective stress invariants instead of approximate ones, as usually assumed in the existing literature, and applies to the more general case where the out-of-plane (vertical) in situ stress may be different from the in-plane (horizontal) one. The results show clearly that the stress history (overconsolidation ratio) has a significant influence on the stress and pore pressure distributions around the cavity. The present solution provides an exact and realistic theoretical framework for predicting the soil behaviour around the cylindrical cavity, with applications to the interpretation of pressuremeter tests and to pile installation problems. It also serves as a valuable benchmark for verifying various cavity expansion numerical methods involving the critical state plasticity model. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.P.027

Liquefaction and cyclic softening potential of soils – a unified piezocone penetration testing-based approach / C. S. Ku in Géotechnique, Vol. 62 N° 5 (Mai 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 457 –461 Titre : Liquefaction and cyclic softening potential of soils – a unified piezocone penetration testing-based approach Type de document : texte imprimé Auteurs : C. S. Ku, Auteur ; C. H. Juang, Auteur Année de publication : 2012 Article en page(s) : pp. 457 –461 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Soil  classification  In  situ  testing  Liquefaction Résumé : Simplified procedures have been widely accepted and used in practice for assessing cyclic liquefaction resistance of sands. Extension of the simplified procedures for assessing liquefaction resistance of fine-grained soils has not achieved the same degree of success. It would be ideal to have a unified model that is based on in situ testing and is applicable to both sand-like and clay-like soils. This note examines one such model and extends its use to both sand-like and clay-like soils. Herein, verification of this unified model using field data from Adapazari, Turkey after the 1999 earthquake is documented along with comparisons with existing models. Satisfactory results are obtained, which shows that the proposed piezocone penetration test (CPTu)-based model is applicable to both sand-like and clay-like soils. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.044 [article] Liquefaction and cyclic softening potential of soils – a unified piezocone penetration testing-based approach [texte imprimé] / C. S. Ku, Auteur ; C. H. Juang, Auteur . - 2012 . - pp. 457 –461. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 457 –461 Mots-clés : Soil  classification  In  situ  testing  Liquefaction Résumé : Simplified procedures have been widely accepted and used in practice for assessing cyclic liquefaction resistance of sands. Extension of the simplified procedures for assessing liquefaction resistance of fine-grained soils has not achieved the same degree of success. It would be ideal to have a unified model that is based on in situ testing and is applicable to both sand-like and clay-like soils. This note examines one such model and extends its use to both sand-like and clay-like soils. Herein, verification of this unified model using field data from Adapazari, Turkey after the 1999 earthquake is documented along with comparisons with existing models. Satisfactory results are obtained, which shows that the proposed piezocone penetration test (CPTu)-based model is applicable to both sand-like and clay-like soils. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.044

Exemplaires

Bibliothèque Ecole Nationale Polytechnique d'Alger

Accueil

Se connecter

Météo

Adresse