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Ajouter le résultat dans votre panierDatabase assessment of CPT-based design methods for axial capacity of driven piles in siliceous sands / James A. Schneider in Journal of geotechnical and geoenvironmental engineering, Vol. 134 n°9 (Septembre 2008)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1227–1244
Titre : Database assessment of CPT-based design methods for axial capacity of driven piles in siliceous sands Type de document : texte imprimé Auteurs : James A. Schneider, Auteur Année de publication : 2008 Article en page(s) : pp. 1227–1244 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Driven piles Cone penetration tests Foundation design Compression Sand Pile load tests Databases Résumé : Numerous cone penetration test (CPT)-based methods exist for calculation of the axial pile capacity in sands, but no clear guidance is presently available to assist designers in the selection of the most appropriate method. To assist in this regard, this paper examines the predictive performance of a range of pile design methods against a newly compiled database of static load tests on driven piles in siliceous sands with adjacent CPT profiles. Seven driven pile design methods are considered, including the conventional American Petroleum Institute (API) approach, simplified CPT alpha methods, and four new CPT-based methods, which are now presented in the commentary of the 22nd edition of the API recommendations. Mean and standard deviation database statistics for the design methods are presented for the entire 77 pile database, as well as for smaller subset databases separated by pile material (steel and concrete), end condition (open versus closed), and direction of loading (tension versus compression). Certain methods are seen to exhibit bias toward length, relative density, cone tip resistance, and pile end condition. Other methods do not exhibit any apparent bias (even though their formulations differ significantly) due to the limited size of the database subsets and the large number of factors known to influence pile capacity in sand. The database statistics for the best performing methods are substantially better than those for the API approach and the simplified alpha methods. Improved predictive reliability will emerge with an extension of the database and the inclusion of additional important controlling factors affecting capacity. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2812 [...] [article] Database assessment of CPT-based design methods for axial capacity of driven piles in siliceous sands [texte imprimé] / James A. Schneider, Auteur . - 2008 . - pp. 1227–1244.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1227–1244
Mots-clés : Driven piles Cone penetration tests Foundation design Compression Sand Pile load tests Databases Résumé : Numerous cone penetration test (CPT)-based methods exist for calculation of the axial pile capacity in sands, but no clear guidance is presently available to assist designers in the selection of the most appropriate method. To assist in this regard, this paper examines the predictive performance of a range of pile design methods against a newly compiled database of static load tests on driven piles in siliceous sands with adjacent CPT profiles. Seven driven pile design methods are considered, including the conventional American Petroleum Institute (API) approach, simplified CPT alpha methods, and four new CPT-based methods, which are now presented in the commentary of the 22nd edition of the API recommendations. Mean and standard deviation database statistics for the design methods are presented for the entire 77 pile database, as well as for smaller subset databases separated by pile material (steel and concrete), end condition (open versus closed), and direction of loading (tension versus compression). Certain methods are seen to exhibit bias toward length, relative density, cone tip resistance, and pile end condition. Other methods do not exhibit any apparent bias (even though their formulations differ significantly) due to the limited size of the database subsets and the large number of factors known to influence pile capacity in sand. The database statistics for the best performing methods are substantially better than those for the API approach and the simplified alpha methods. Improved predictive reliability will emerge with an extension of the database and the inclusion of additional important controlling factors affecting capacity. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2812 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1245–1260
Titre : Effects of tip location and shielding on piles in consolidating ground Type de document : texte imprimé Auteurs : Charles W.W. Ng, Auteur ; Harry G. Poulos, Auteur ; Vincent S. H. Chan, Auteur Année de publication : 2008 Article en page(s) : pp. 1245–1260 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Centrifuge models Numerical models Downdrag Friction Pile foundations Résumé : Pile foundations located within consolidating ground are commonly subjected to negative skin friction (NSF) and failures of pile foundations related to dragload (compressive force) and downdrag (pile settlement) have been reported in the literature. This paper reports the results of four centrifuge model tests, which were undertaken to achieve two objectives: first, to investigate the response of a single pile subjected to NSF with different pile tip location with respect to the end-bearing stratum layer; and second, to study the behavior of floating piles subjected to NSF with and without shielding by sacrificing piles. In addition, three-dimensional numerical analyses of the centrifuge model tests were carried out with elastoplastic slip considered at the pile-soil interface. The measured maximum β value at unprotected single end-bearing and floating pile was similar and slightly smaller than 0.3. On the contrary, smaller β values of 0.1 and 0.2 were mobilized at the shielded center piles for pile spacings of 5.0 d and 6.0 d , respectively. The measured maximum dragload of the center pile in the group at 5.0 d and 6.0 d spacing was only 53% and 75% of the measured maximum dragload of an isolated single pile, respectively. Correspondingly, the measured downdrag of the center pile was reduced to about 57% and 80% of the isolated single pile. Based on the numerical analyses, it is revealed that sacrificing piles “hang up” the soil between the piles in the group and, thus, the vertical effective stress in the soil so reduced, as is the horizontal effective stress acting on the center pile. This “hang-up” effect reduces with an increase in pile spacing. For a given pile spacing, shielding effect on dragload is larger than that on downdrag. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2812 [...] [article] Effects of tip location and shielding on piles in consolidating ground [texte imprimé] / Charles W.W. Ng, Auteur ; Harry G. Poulos, Auteur ; Vincent S. H. Chan, Auteur . - 2008 . - pp. 1245–1260.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1245–1260
Mots-clés : Centrifuge models Numerical models Downdrag Friction Pile foundations Résumé : Pile foundations located within consolidating ground are commonly subjected to negative skin friction (NSF) and failures of pile foundations related to dragload (compressive force) and downdrag (pile settlement) have been reported in the literature. This paper reports the results of four centrifuge model tests, which were undertaken to achieve two objectives: first, to investigate the response of a single pile subjected to NSF with different pile tip location with respect to the end-bearing stratum layer; and second, to study the behavior of floating piles subjected to NSF with and without shielding by sacrificing piles. In addition, three-dimensional numerical analyses of the centrifuge model tests were carried out with elastoplastic slip considered at the pile-soil interface. The measured maximum β value at unprotected single end-bearing and floating pile was similar and slightly smaller than 0.3. On the contrary, smaller β values of 0.1 and 0.2 were mobilized at the shielded center piles for pile spacings of 5.0 d and 6.0 d , respectively. The measured maximum dragload of the center pile in the group at 5.0 d and 6.0 d spacing was only 53% and 75% of the measured maximum dragload of an isolated single pile, respectively. Correspondingly, the measured downdrag of the center pile was reduced to about 57% and 80% of the isolated single pile. Based on the numerical analyses, it is revealed that sacrificing piles “hang up” the soil between the piles in the group and, thus, the vertical effective stress in the soil so reduced, as is the horizontal effective stress acting on the center pile. This “hang-up” effect reduces with an increase in pile spacing. For a given pile spacing, shielding effect on dragload is larger than that on downdrag. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2812 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1261–1271
Titre : Assessing well drilling disturbance effects on offshore foundation piles in clay Type de document : texte imprimé Année de publication : 2008 Article en page(s) : pp. 1261–1271 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Offshore structures Pile foundations Marine clays Disturbances Offshore drilling Numerical analysis Résumé : It is widely recognized that hydrocarbon well drilling from offshore platforms affects the surrounding ground. In clays, the level of disturbance can be severe when sections of open well collapse during drilling, impeding fluid return to the seabed (termed “packing-off”), and drilling fluid pressure is increased in order to obtain a breakthrough return path for the fluid. Significant swelling and hydraulic fracturing can take place in the surrounding soil mass. With time the excess pore pressures will dissipate and could cause increases in pore pressures far from the wells, potentially affecting areas occupied by the platform’s foundation piles. There is no established procedure to quantify the impact of such processes on foundation performance. This paper presents a numerical approach that involves a series of finite-element analyses in which drilling disturbance is treated as an idealized fluid injection process. The entry of pressurized drilling water into progressively enlarging fractured disturbed zones, and hence into the surrounding soil mass, is simulated with two- and three-dimensional nonlinear finite-element (FE) models, without modeling the actual hydraulic fracturing processes. The analyses make use of key observations made in the field at a piled offshore platform. The FE analyses predict marginal foundation capacity reductions, as well as significant global vertical and horizontal movements developing around the piles. It is demonstrated that the ground movement predictions are heavily influenced by the degree of geometric idealization. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2812 [...] [article] Assessing well drilling disturbance effects on offshore foundation piles in clay [texte imprimé] . - 2008 . - pp. 1261–1271.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1261–1271
Mots-clés : Offshore structures Pile foundations Marine clays Disturbances Offshore drilling Numerical analysis Résumé : It is widely recognized that hydrocarbon well drilling from offshore platforms affects the surrounding ground. In clays, the level of disturbance can be severe when sections of open well collapse during drilling, impeding fluid return to the seabed (termed “packing-off”), and drilling fluid pressure is increased in order to obtain a breakthrough return path for the fluid. Significant swelling and hydraulic fracturing can take place in the surrounding soil mass. With time the excess pore pressures will dissipate and could cause increases in pore pressures far from the wells, potentially affecting areas occupied by the platform’s foundation piles. There is no established procedure to quantify the impact of such processes on foundation performance. This paper presents a numerical approach that involves a series of finite-element analyses in which drilling disturbance is treated as an idealized fluid injection process. The entry of pressurized drilling water into progressively enlarging fractured disturbed zones, and hence into the surrounding soil mass, is simulated with two- and three-dimensional nonlinear finite-element (FE) models, without modeling the actual hydraulic fracturing processes. The analyses make use of key observations made in the field at a piled offshore platform. The FE analyses predict marginal foundation capacity reductions, as well as significant global vertical and horizontal movements developing around the piles. It is demonstrated that the ground movement predictions are heavily influenced by the degree of geometric idealization. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2812 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1272–1279
Titre : Roughness and unit side resistances of drilled shafts socketed in clay shale and limestone Type de document : texte imprimé Auteurs : Moon S. Nam, Auteur ; Cumaraswamy Vipulanandan, Auteur Année de publication : 2008 Article en page(s) : pp. 1272–1279 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Roughness Drilling Drilled shafts Clays Rocks Limestone Shale Résumé : Rock socketed drilled shafts are being used increasingly to support heavily loaded structures. Rock sockets provide resistance to the load through a combination of side and base resistances. In this study, the effect of drilling tools such as an auger and a core barrel on the unit side resistance was investigated. A total of four field studies were performed on clay shale (compressive strength of 1–2MPa ) and limestone (compressive strength of 10MPa ). Borehole roughnesses produced by the different types of drilling tools in clay shale and limestone were measured using a laser borehole roughness profiler developed in this study to measure roughness to 0.5mm in the boreholes. Based on the results of this study, it was observed that the drilling tools developed different socket roughnesses, which in turn affected the side resistances of the rock socketed drilled shafts. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2812 [...] [article] Roughness and unit side resistances of drilled shafts socketed in clay shale and limestone [texte imprimé] / Moon S. Nam, Auteur ; Cumaraswamy Vipulanandan, Auteur . - 2008 . - pp. 1272–1279.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1272–1279
Mots-clés : Roughness Drilling Drilled shafts Clays Rocks Limestone Shale Résumé : Rock socketed drilled shafts are being used increasingly to support heavily loaded structures. Rock sockets provide resistance to the load through a combination of side and base resistances. In this study, the effect of drilling tools such as an auger and a core barrel on the unit side resistance was investigated. A total of four field studies were performed on clay shale (compressive strength of 1–2MPa ) and limestone (compressive strength of 10MPa ). Borehole roughnesses produced by the different types of drilling tools in clay shale and limestone were measured using a laser borehole roughness profiler developed in this study to measure roughness to 0.5mm in the boreholes. Based on the results of this study, it was observed that the drilling tools developed different socket roughnesses, which in turn affected the side resistances of the rock socketed drilled shafts. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2812 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1280-1289
Titre : Experimental investigation of grouted helical piers for use in foundation rehabilitation Type de document : texte imprimé Auteurs : Yueying Bian, Auteur ; Hutchinson, Tara C., Auteur ; Dan Wilson, Auteur Année de publication : 2008 Article en page(s) : pp. 1280-1289 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Grouting Piers Centrifuge models Rehabilitation Deep foundations Résumé : Building rehabilitation is critical for numerous older urban areas, many of which have inadequate foundations to support new demands. Consequently, development of practical methods to strengthen existing foundations is crucial. In engineering practice, both subsurface grouting and helical piers have been widely used to address these issues by strengthening the foundation. If the solid shaft of a typical helical pier is replaced by a hollow shaft, then helical piers provide the ability to deliver grout. It is hypothesized that these grouted helical pier systems could address foundation strengthening needs. This paper presents findings from an exploratory research program where grouting and pier placement tools were developed and tested on the large geotechnical centrifuge at the University of California, Davis. Experimental methods and procedures developed are presented, and observations regarding the formation of grout bulbs under different conditions are analyzed. Physical observation of the test specimens indicates that average grout bulb diameters of 0.6–1.9 times the helix diameter (Dh) are attainable. For similar grout mixes, 20–50% larger grout bulbs can be attained by adding just a modest amount of injection pressure. Future research may use these results to develop load performance data. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2812 [...] [article] Experimental investigation of grouted helical piers for use in foundation rehabilitation [texte imprimé] / Yueying Bian, Auteur ; Hutchinson, Tara C., Auteur ; Dan Wilson, Auteur . - 2008 . - pp. 1280-1289.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1280-1289
Mots-clés : Grouting Piers Centrifuge models Rehabilitation Deep foundations Résumé : Building rehabilitation is critical for numerous older urban areas, many of which have inadequate foundations to support new demands. Consequently, development of practical methods to strengthen existing foundations is crucial. In engineering practice, both subsurface grouting and helical piers have been widely used to address these issues by strengthening the foundation. If the solid shaft of a typical helical pier is replaced by a hollow shaft, then helical piers provide the ability to deliver grout. It is hypothesized that these grouted helical pier systems could address foundation strengthening needs. This paper presents findings from an exploratory research program where grouting and pier placement tools were developed and tested on the large geotechnical centrifuge at the University of California, Davis. Experimental methods and procedures developed are presented, and observations regarding the formation of grout bulbs under different conditions are analyzed. Physical observation of the test specimens indicates that average grout bulb diameters of 0.6–1.9 times the helix diameter (Dh) are attainable. For similar grout mixes, 20–50% larger grout bulbs can be attained by adding just a modest amount of injection pressure. Future research may use these results to develop load performance data. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2812 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1290–1298
Titre : Statnamic damping coefficient : numerical modeling approach Type de document : texte imprimé Auteurs : Michael Stokes, Auteur ; Gray Mullins, Auteur ; Carl Ealy, Auteur Année de publication : 2008 Article en page(s) : pp. 1290–1298 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Cohesionless soils Damping Pile load tests Load tests Soil-pile interaction Résumé : The damping associated with dynamic or statnamic tests has typically been over simplified to provide a “catch-all” factor for those responses that could not be fully accounted for using present analyses. This factor has historically been considered constant for a given pile–soil system, but recent investigations as well as previous case studies show the plausibility of another explanation. This study hypothesizes that damping is more closely associated with the increase in strain and not the total strain. Therein, the change in the volumetric strain is being scrutinized to investigate its relationship to damping. To validate this assumption, a numerical model is created which simulates the testing of a full-scale drilled shaft and results analyzed to determine the extent of the zone of influence and volumetric contribution to damping En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2812 [...] [article] Statnamic damping coefficient : numerical modeling approach [texte imprimé] / Michael Stokes, Auteur ; Gray Mullins, Auteur ; Carl Ealy, Auteur . - 2008 . - pp. 1290–1298.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1290–1298
Mots-clés : Cohesionless soils Damping Pile load tests Load tests Soil-pile interaction Résumé : The damping associated with dynamic or statnamic tests has typically been over simplified to provide a “catch-all” factor for those responses that could not be fully accounted for using present analyses. This factor has historically been considered constant for a given pile–soil system, but recent investigations as well as previous case studies show the plausibility of another explanation. This study hypothesizes that damping is more closely associated with the increase in strain and not the total strain. Therein, the change in the volumetric strain is being scrutinized to investigate its relationship to damping. To validate this assumption, a numerical model is created which simulates the testing of a full-scale drilled shaft and results analyzed to determine the extent of the zone of influence and volumetric contribution to damping En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2812 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1299–1310
Titre : Effect of footing width on bearing capacity factor Nγ for smooth strip footings Type de document : texte imprimé Auteurs : Jyant Kumar, Auteur ; V. N. Khatri, Auteur Année de publication : 2008 Article en page(s) : pp. 1299–1310 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Footings Bearing capacity Failures Foundations Limit analysis Numerical analysis Optimization Résumé : By incorporating the variation of soil friction angle (ϕ) with mean principal stress (σm) , the effect of footing width (B) on bearing capacity factor Nγ was examined for a smooth strip footing placed on a granular medium without any surcharge pressure. The analysis was performed by means of a numerical lower bound limit analysis in conjunction with finite-elements and linear programming. An iterative computational procedure was framed to account for the dependency of ϕ on σm . Two well-defined ϕ–σm curves from literature associated with Hoston and Toyora sands, corresponding to relative density of 18 and 74.5%, respectively, were used. The magnitude of Nγ was obtained for different footing widths, covering almost the entire range of model and field footing sizes. It was noted that for B greater than about 0.4m , it is possible to relate Nγ with B approximately in a linear fashion on a log–log scale. Further, it was seen that if an average value of ϕ along the footing–soil interface is obtained, it is possible to estimate a reasonable magnitude of Nγ for a given footing width provided the relationship between ϕ and σm is specified for the given material. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2812 [...] [article] Effect of footing width on bearing capacity factor Nγ for smooth strip footings [texte imprimé] / Jyant Kumar, Auteur ; V. N. Khatri, Auteur . - 2008 . - pp. 1299–1310.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1299–1310
Mots-clés : Footings Bearing capacity Failures Foundations Limit analysis Numerical analysis Optimization Résumé : By incorporating the variation of soil friction angle (ϕ) with mean principal stress (σm) , the effect of footing width (B) on bearing capacity factor Nγ was examined for a smooth strip footing placed on a granular medium without any surcharge pressure. The analysis was performed by means of a numerical lower bound limit analysis in conjunction with finite-elements and linear programming. An iterative computational procedure was framed to account for the dependency of ϕ on σm . Two well-defined ϕ–σm curves from literature associated with Hoston and Toyora sands, corresponding to relative density of 18 and 74.5%, respectively, were used. The magnitude of Nγ was obtained for different footing widths, covering almost the entire range of model and field footing sizes. It was noted that for B greater than about 0.4m , it is possible to relate Nγ with B approximately in a linear fashion on a log–log scale. Further, it was seen that if an average value of ϕ along the footing–soil interface is obtained, it is possible to estimate a reasonable magnitude of Nγ for a given footing width provided the relationship between ϕ and σm is specified for the given material. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2812 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1311–1318
Titre : Modified direct shear test for anisotropic strength of sand Type de document : texte imprimé Auteurs : Peijun Guo, Auteur Année de publication : 2008 Article en page(s) : pp. 1311–1318 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Shear tests Shear strength Anisotropy Granular materials Sedimentation Résumé : This paper presents a simple method to estimate the directional dependency of granular soil strength using a modified shear box and a special specimen preparation procedure. This method is used to investigate the strength anisotropy of granular materials with particle shapes varying from spherical to angular. The experimental results show that the friction angle of granular materials varies with the orientation of shear plane relative to the bedding plane, and the degree of anisotropy is affected by particle shape. Comparison of the data from direct shear tests in this study with those of plane strain and torsional simple shear tests in the literature shows that direct shear using the modified direct shear box can reasonably capture the directional dependency of the friction angle for cohesionless materials. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Modified direct shear test for anisotropic strength of sand [texte imprimé] / Peijun Guo, Auteur . - 2008 . - pp. 1311–1318.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1311–1318
Mots-clés : Shear tests Shear strength Anisotropy Granular materials Sedimentation Résumé : This paper presents a simple method to estimate the directional dependency of granular soil strength using a modified shear box and a special specimen preparation procedure. This method is used to investigate the strength anisotropy of granular materials with particle shapes varying from spherical to angular. The experimental results show that the friction angle of granular materials varies with the orientation of shear plane relative to the bedding plane, and the degree of anisotropy is affected by particle shape. Comparison of the data from direct shear tests in this study with those of plane strain and torsional simple shear tests in the literature shows that direct shear using the modified direct shear box can reasonably capture the directional dependency of the friction angle for cohesionless materials. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1319–1326
Titre : Measurement of frequency-dependent dynamic properties of soils using the resonant-column device Type de document : texte imprimé Auteurs : Z. H. Khan, Auteur ; G. Cascante, Auteur ; M. H. El Naggar, Auteur Année de publication : 2008 Article en page(s) : pp. 1319–1326 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Resonance Velocity Damping Soil dynamics Soil properties Soil tests Résumé : Dynamic properties of soils are commonly evaluated at resonance; thus, their variation with frequency is difficult to measure. A nonresonance (NR) method has been recently used for testing soils at low frequencies and strain levels below the linear threshold shear strain. However, the NR method has not been validated with the standard resonant method for different shear strain levels. In this study, the NR method is used to measure the dynamic properties of soils at low and midstrain levels for a maximum frequency bandwidth between 5 and 100Hz using the resonant-column device. A new transfer function (NTF) equation is introduced to compare the dynamic properties measured using the NR method and the conventional transfer function approach. Experimental results for two sands and a sand–bentonite–mud mixture are presented for different strain and stress confinement levels. Results from the NR method compare well with the standard resonant column method at the resonant frequency if the strain levels are the same. The NTF approach can be used to measure the dependence of phase velocity of shear waves with frequency. However, the NTF method cannot be used to measure the variation of material damping with frequency. On the other hand, the NR method can be used to measure the degradation curves of wave velocity and material damping ratio as a function of frequency. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Measurement of frequency-dependent dynamic properties of soils using the resonant-column device [texte imprimé] / Z. H. Khan, Auteur ; G. Cascante, Auteur ; M. H. El Naggar, Auteur . - 2008 . - pp. 1319–1326.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1319–1326
Mots-clés : Resonance Velocity Damping Soil dynamics Soil properties Soil tests Résumé : Dynamic properties of soils are commonly evaluated at resonance; thus, their variation with frequency is difficult to measure. A nonresonance (NR) method has been recently used for testing soils at low frequencies and strain levels below the linear threshold shear strain. However, the NR method has not been validated with the standard resonant method for different shear strain levels. In this study, the NR method is used to measure the dynamic properties of soils at low and midstrain levels for a maximum frequency bandwidth between 5 and 100Hz using the resonant-column device. A new transfer function (NTF) equation is introduced to compare the dynamic properties measured using the NR method and the conventional transfer function approach. Experimental results for two sands and a sand–bentonite–mud mixture are presented for different strain and stress confinement levels. Results from the NR method compare well with the standard resonant column method at the resonant frequency if the strain levels are the same. The NTF approach can be used to measure the dependence of phase velocity of shear waves with frequency. However, the NTF method cannot be used to measure the variation of material damping with frequency. On the other hand, the NR method can be used to measure the degradation curves of wave velocity and material damping ratio as a function of frequency. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1319–1326
Titre : Measurement of frequency-dependent dynamic properties of soils using the resonant-column device Type de document : texte imprimé Auteurs : Z. H. Khan, Auteur ; G. Cascante, Auteur ; M. H. El Naggar, Auteur Année de publication : 2008 Article en page(s) : pp. 1319–1326 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Resonance Velocity Damping Soil dynamics Soil properties Soil tests Résumé : Dynamic properties of soils are commonly evaluated at resonance; thus, their variation with frequency is difficult to measure. A nonresonance (NR) method has been recently used for testing soils at low frequencies and strain levels below the linear threshold shear strain. However, the NR method has not been validated with the standard resonant method for different shear strain levels. In this study, the NR method is used to measure the dynamic properties of soils at low and midstrain levels for a maximum frequency bandwidth between 5 and 100Hz using the resonant-column device. A new transfer function (NTF) equation is introduced to compare the dynamic properties measured using the NR method and the conventional transfer function approach. Experimental results for two sands and a sand–bentonite–mud mixture are presented for different strain and stress confinement levels. Results from the NR method compare well with the standard resonant column method at the resonant frequency if the strain levels are the same. The NTF approach can be used to measure the dependence of phase velocity of shear waves with frequency. However, the NTF method cannot be used to measure the variation of material damping with frequency. On the other hand, the NR method can be used to measure the degradation curves of wave velocity and material damping ratio as a function of frequency. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Measurement of frequency-dependent dynamic properties of soils using the resonant-column device [texte imprimé] / Z. H. Khan, Auteur ; G. Cascante, Auteur ; M. H. El Naggar, Auteur . - 2008 . - pp. 1319–1326.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1319–1326
Mots-clés : Resonance Velocity Damping Soil dynamics Soil properties Soil tests Résumé : Dynamic properties of soils are commonly evaluated at resonance; thus, their variation with frequency is difficult to measure. A nonresonance (NR) method has been recently used for testing soils at low frequencies and strain levels below the linear threshold shear strain. However, the NR method has not been validated with the standard resonant method for different shear strain levels. In this study, the NR method is used to measure the dynamic properties of soils at low and midstrain levels for a maximum frequency bandwidth between 5 and 100Hz using the resonant-column device. A new transfer function (NTF) equation is introduced to compare the dynamic properties measured using the NR method and the conventional transfer function approach. Experimental results for two sands and a sand–bentonite–mud mixture are presented for different strain and stress confinement levels. Results from the NR method compare well with the standard resonant column method at the resonant frequency if the strain levels are the same. The NTF approach can be used to measure the dependence of phase velocity of shear waves with frequency. However, the NTF method cannot be used to measure the variation of material damping with frequency. On the other hand, the NR method can be used to measure the degradation curves of wave velocity and material damping ratio as a function of frequency. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1327–1338
Titre : Rapid pullout test of soil nail Type de document : texte imprimé Auteurs : S. A. Tan, Auteur ; P. H. Ooi, Auteur ; Park, T. S., Auteur Année de publication : 2008 Article en page(s) : pp. 1327–1338 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Soil nailing Pull-out resistance Shaft resistance Piles Damping Résumé : This technical paper describes the rapid pullout response of soil nail embedded in dry clean sand. In the rapid pullout test, soil nail is pullout by a tensile impulse load with loading duration that is long enough to eliminate the influence of the stress wave propagation phenomenon. The results of these experiments showed the influence of loading rate on pullout response is highly dependent on the roughness condition of the nail surface. For rough nail, the prepeak rapid pullout response was significantly stiffer in the load-displacement characteristic and higher in peak pullout strength when compared to the corresponding quasi-static pullout response. While for a smooth nail, a negligible difference between rapid and quasi-static pullout response was noticed. In light of these limited experimental results, the radiation damping effect appears to be the dominant contributor to the enhancements in prepeak rapid pullout response of rough nail. “Actual” damping coefficient that quantifies the damping resistance mobilized in a rapid pullout test was found not to be constant but to decrease with the increase in pullout displacement. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Rapid pullout test of soil nail [texte imprimé] / S. A. Tan, Auteur ; P. H. Ooi, Auteur ; Park, T. S., Auteur . - 2008 . - pp. 1327–1338.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1327–1338
Mots-clés : Soil nailing Pull-out resistance Shaft resistance Piles Damping Résumé : This technical paper describes the rapid pullout response of soil nail embedded in dry clean sand. In the rapid pullout test, soil nail is pullout by a tensile impulse load with loading duration that is long enough to eliminate the influence of the stress wave propagation phenomenon. The results of these experiments showed the influence of loading rate on pullout response is highly dependent on the roughness condition of the nail surface. For rough nail, the prepeak rapid pullout response was significantly stiffer in the load-displacement characteristic and higher in peak pullout strength when compared to the corresponding quasi-static pullout response. While for a smooth nail, a negligible difference between rapid and quasi-static pullout response was noticed. In light of these limited experimental results, the radiation damping effect appears to be the dominant contributor to the enhancements in prepeak rapid pullout response of rough nail. “Actual” damping coefficient that quantifies the damping resistance mobilized in a rapid pullout test was found not to be constant but to decrease with the increase in pullout displacement. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1327–1338
Titre : Rapid pullout test of soil nail Type de document : texte imprimé Auteurs : S. A. Tan, Auteur ; P. H. Ooi, Auteur ; Park, T. S., Auteur Année de publication : 2008 Article en page(s) : pp. 1327–1338 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Soil nailing Pull-out resistance Shaft resistance Piles Damping Résumé : This technical paper describes the rapid pullout response of soil nail embedded in dry clean sand. In the rapid pullout test, soil nail is pullout by a tensile impulse load with loading duration that is long enough to eliminate the influence of the stress wave propagation phenomenon. The results of these experiments showed the influence of loading rate on pullout response is highly dependent on the roughness condition of the nail surface. For rough nail, the prepeak rapid pullout response was significantly stiffer in the load-displacement characteristic and higher in peak pullout strength when compared to the corresponding quasi-static pullout response. While for a smooth nail, a negligible difference between rapid and quasi-static pullout response was noticed. In light of these limited experimental results, the radiation damping effect appears to be the dominant contributor to the enhancements in prepeak rapid pullout response of rough nail. “Actual” damping coefficient that quantifies the damping resistance mobilized in a rapid pullout test was found not to be constant but to decrease with the increase in pullout displacement. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Rapid pullout test of soil nail [texte imprimé] / S. A. Tan, Auteur ; P. H. Ooi, Auteur ; Park, T. S., Auteur . - 2008 . - pp. 1327–1338.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1327–1338
Mots-clés : Soil nailing Pull-out resistance Shaft resistance Piles Damping Résumé : This technical paper describes the rapid pullout response of soil nail embedded in dry clean sand. In the rapid pullout test, soil nail is pullout by a tensile impulse load with loading duration that is long enough to eliminate the influence of the stress wave propagation phenomenon. The results of these experiments showed the influence of loading rate on pullout response is highly dependent on the roughness condition of the nail surface. For rough nail, the prepeak rapid pullout response was significantly stiffer in the load-displacement characteristic and higher in peak pullout strength when compared to the corresponding quasi-static pullout response. While for a smooth nail, a negligible difference between rapid and quasi-static pullout response was noticed. In light of these limited experimental results, the radiation damping effect appears to be the dominant contributor to the enhancements in prepeak rapid pullout response of rough nail. “Actual” damping coefficient that quantifies the damping resistance mobilized in a rapid pullout test was found not to be constant but to decrease with the increase in pullout displacement. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1339-1347
Titre : Influence of overburden pressure on soil–nail pullout resistance in a compacted fill Type de document : texte imprimé Auteurs : Li-Jun Su, Auteur ; Terence C. F. Chan, Auteur Année de publication : 2008 Article en page(s) : pp. 1339-1347 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Soil nailing Shear resistance Fills Soil compaction Shear strength Soil pressure Résumé : Soil nailing has been widely used in many places in the world in the last two decades because of its technical and economical advantages. The nail–soil interface shear strength is an important parameter in soil nail design. This parameter is governed by a number of factors, among which the influence of the overburden pressure (or soil depth) is the most controversial. There are differing views concerning the effect of overburden on the nail–soil interface shear strength. In order to examine the influence of the overburden pressure, a series of laboratory pullout tests on soil nails installed in compacted completely decomposed granite fill have been conducted using two pullout boxes. Numerical simulations have also been carried out and the results are compared with the pullout test data. The procedures of the pullout tests and new features of the pullout boxes used are briefly described. Changes of the vertical stress in soil close to the nail throughout the course of soil nail installation and pullout are presented and discussed in detail. It is observed from the results of this study that the installation process of soil nail induced significant vertical stress changes in soil around the soil nails, and that the soil nail pullout shear resistance is independent of the overburden pressure (or soil depth). En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Influence of overburden pressure on soil–nail pullout resistance in a compacted fill [texte imprimé] / Li-Jun Su, Auteur ; Terence C. F. Chan, Auteur . - 2008 . - pp. 1339-1347.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1339-1347
Mots-clés : Soil nailing Shear resistance Fills Soil compaction Shear strength Soil pressure Résumé : Soil nailing has been widely used in many places in the world in the last two decades because of its technical and economical advantages. The nail–soil interface shear strength is an important parameter in soil nail design. This parameter is governed by a number of factors, among which the influence of the overburden pressure (or soil depth) is the most controversial. There are differing views concerning the effect of overburden on the nail–soil interface shear strength. In order to examine the influence of the overburden pressure, a series of laboratory pullout tests on soil nails installed in compacted completely decomposed granite fill have been conducted using two pullout boxes. Numerical simulations have also been carried out and the results are compared with the pullout test data. The procedures of the pullout tests and new features of the pullout boxes used are briefly described. Changes of the vertical stress in soil close to the nail throughout the course of soil nail installation and pullout are presented and discussed in detail. It is observed from the results of this study that the installation process of soil nail induced significant vertical stress changes in soil around the soil nails, and that the soil nail pullout shear resistance is independent of the overburden pressure (or soil depth). En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1348-1363
Titre : Calibration of reliability-based resistance factors for flush drilled soil anchors in Taipei basin Type de document : texte imprimé Auteurs : Jianye Ching, Auteur ; Hung-Jiun Liao, Auteur ; Chia-Wei Sue, Auteur Année de publication : 2008 Article en page(s) : pp. 1348-1363 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Anchors Pull-out resistance Safety factors Taiwan Calibration Drilling Résumé : The goal of this research is to calibrate the reliability-based resistance factor of flush drilled soil anchors for their ultimate pullout capacities based on in situ anchor pullout test data in the alluvial soil underlying the Taipei Basin. Efforts are taken to quantify the uncertainties with a full probabilistic analysis approach. The resistance factor is calibrated based on the in situ test results of 46 anchors with a rigorous theoretical approach which constructs the relationship between the resistance factor and failure probability. With this relationship, the reliability corresponding to the code regulation can be verified. From the results of the analysis, it is found that the borehole enlargement due to the flush drilling is quite significant: the actual diameter of the fixed anchor end may be much larger than the nominal diameter of the drilling casing. Consequently, the safety factor of 3.0, recommended by most anchor codes, is found to be too conservative. The results should be valuable for reliability-based design of flush drilled soil anchors in the Taipei Basin. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Calibration of reliability-based resistance factors for flush drilled soil anchors in Taipei basin [texte imprimé] / Jianye Ching, Auteur ; Hung-Jiun Liao, Auteur ; Chia-Wei Sue, Auteur . - 2008 . - pp. 1348-1363.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1348-1363
Mots-clés : Anchors Pull-out resistance Safety factors Taiwan Calibration Drilling Résumé : The goal of this research is to calibrate the reliability-based resistance factor of flush drilled soil anchors for their ultimate pullout capacities based on in situ anchor pullout test data in the alluvial soil underlying the Taipei Basin. Efforts are taken to quantify the uncertainties with a full probabilistic analysis approach. The resistance factor is calibrated based on the in situ test results of 46 anchors with a rigorous theoretical approach which constructs the relationship between the resistance factor and failure probability. With this relationship, the reliability corresponding to the code regulation can be verified. From the results of the analysis, it is found that the borehole enlargement due to the flush drilling is quite significant: the actual diameter of the fixed anchor end may be much larger than the nominal diameter of the drilling casing. Consequently, the safety factor of 3.0, recommended by most anchor codes, is found to be too conservative. The results should be valuable for reliability-based design of flush drilled soil anchors in the Taipei Basin. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1364–1374
Titre : Centrifuge modeling of rock-fill embankments on deep loose saturated sand deposits subjected to earthquakes Type de document : texte imprimé Auteurs : L. M. N. Peiris, Auteur ; S. P.G. Madabhushi, Auteur ; A. N. Schofield, Auteur Année de publication : 2008 Article en page(s) : pp. 1364–1374 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Centrifuge models Earthquakes Failures Liquefaction Rock Fills Embankments Sand Résumé : Rockfill is commonly used for construction of artificial islands, breakwaters, jetties, quay walls, coastal defenses, protective barriers for reclaimed land, and even as ship impact protection structures around bridge piers. The economic construction method often involves rock dumping onto loose or liquefiable sediments with little or no ground improvement. Hence in a seismic environment, these rock-fill or rubble mound structures are potentially vulnerable to failure due to pore pressure generation effects of the underlying deposits. This paper presents experimental investigation carried out using dynamic centrifuge modeling to study the seismic performance of rock-fill or rubble mound embankment structures on liquefiable sand deposits. The centrifuge test results indicate that the rock-fill embankments suffer substantial settlement owing to rock-fill penetration into the founding sand deposit assisted by the pore pressure generation effects. This mechanism of failure was not, however, observed for a sand embankment where the particle size distribution is comparable to the foundation. This result has important implications in the design methodologies adopted for rock-fill or rubble mound structures. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Centrifuge modeling of rock-fill embankments on deep loose saturated sand deposits subjected to earthquakes [texte imprimé] / L. M. N. Peiris, Auteur ; S. P.G. Madabhushi, Auteur ; A. N. Schofield, Auteur . - 2008 . - pp. 1364–1374.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1364–1374
Mots-clés : Centrifuge models Earthquakes Failures Liquefaction Rock Fills Embankments Sand Résumé : Rockfill is commonly used for construction of artificial islands, breakwaters, jetties, quay walls, coastal defenses, protective barriers for reclaimed land, and even as ship impact protection structures around bridge piers. The economic construction method often involves rock dumping onto loose or liquefiable sediments with little or no ground improvement. Hence in a seismic environment, these rock-fill or rubble mound structures are potentially vulnerable to failure due to pore pressure generation effects of the underlying deposits. This paper presents experimental investigation carried out using dynamic centrifuge modeling to study the seismic performance of rock-fill or rubble mound embankment structures on liquefiable sand deposits. The centrifuge test results indicate that the rock-fill embankments suffer substantial settlement owing to rock-fill penetration into the founding sand deposit assisted by the pore pressure generation effects. This mechanism of failure was not, however, observed for a sand embankment where the particle size distribution is comparable to the foundation. This result has important implications in the design methodologies adopted for rock-fill or rubble mound structures. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1375–1384
Titre : Suction-controlled laboratory test on resilient modulus of unsaturated compacted subgrade soils Type de document : texte imprimé Auteurs : Shu-Rong Yang, Auteur ; Horn-Da Lin, Auteur ; Kung, Johnson H. S., Auteur Année de publication : 2008 Article en page(s) : pp. 1375–1384 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Subgrades Soil suction Resilient modulus Laboratory tests Unsaturated soils Soil compaction Résumé : Conventionally, the resilient modulus test is conducted in the laboratory under different moisture content in which matric suction is unknown during the test. To investigate the influence of the matric suction on the resilient modulus, this study integrated the suction-controlled testing system and developed a modified testing procedure for the resilient modulus test of unsaturated subgrade soils. Based on the axis-translation technique, two cohesive soils were tested to investigate the effect of matric suction on resilient modulus. In the modified testing procedure, in order to fulfill the equilibrium in matric suction, the number of load cycles at each loading sequence of the resilient modulus test (AASHTO T 292-91) needs to be increased significantly. Experimental data indicate that matric suctions measured in the specimen after consolidation and resilient modulus tests are consistent with the matric suctions deduced from the soil-water characteristic curve corresponding to the same moisture content. In general, the resilient modulus obtained by the suction-controlled resilient modulus test appears to be reasonable. The trends of resilient modulus obtained by the suction-controlled resilient modulus test are consistent with those obtained by the conventional resilient modulus test. However, the suction-controlled resilient modulus test provides better insights that can help in interpreting the test results. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Suction-controlled laboratory test on resilient modulus of unsaturated compacted subgrade soils [texte imprimé] / Shu-Rong Yang, Auteur ; Horn-Da Lin, Auteur ; Kung, Johnson H. S., Auteur . - 2008 . - pp. 1375–1384.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1375–1384
Mots-clés : Subgrades Soil suction Resilient modulus Laboratory tests Unsaturated soils Soil compaction Résumé : Conventionally, the resilient modulus test is conducted in the laboratory under different moisture content in which matric suction is unknown during the test. To investigate the influence of the matric suction on the resilient modulus, this study integrated the suction-controlled testing system and developed a modified testing procedure for the resilient modulus test of unsaturated subgrade soils. Based on the axis-translation technique, two cohesive soils were tested to investigate the effect of matric suction on resilient modulus. In the modified testing procedure, in order to fulfill the equilibrium in matric suction, the number of load cycles at each loading sequence of the resilient modulus test (AASHTO T 292-91) needs to be increased significantly. Experimental data indicate that matric suctions measured in the specimen after consolidation and resilient modulus tests are consistent with the matric suctions deduced from the soil-water characteristic curve corresponding to the same moisture content. In general, the resilient modulus obtained by the suction-controlled resilient modulus test appears to be reasonable. The trends of resilient modulus obtained by the suction-controlled resilient modulus test are consistent with those obtained by the conventional resilient modulus test. However, the suction-controlled resilient modulus test provides better insights that can help in interpreting the test results. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1375–1384
Titre : Suction-controlled laboratory test on resilient modulus of unsaturated compacted subgrade soils Type de document : texte imprimé Auteurs : Shu-Rong Yang, Auteur ; Horn-Da Lin, Auteur ; Kung, Johnson H. S., Auteur Année de publication : 2008 Article en page(s) : pp. 1375–1384 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Subgrades Soil suction Resilient modulus Laboratory tests Unsaturated soils Soil compaction Résumé : Conventionally, the resilient modulus test is conducted in the laboratory under different moisture content in which matric suction is unknown during the test. To investigate the influence of the matric suction on the resilient modulus, this study integrated the suction-controlled testing system and developed a modified testing procedure for the resilient modulus test of unsaturated subgrade soils. Based on the axis-translation technique, two cohesive soils were tested to investigate the effect of matric suction on resilient modulus. In the modified testing procedure, in order to fulfill the equilibrium in matric suction, the number of load cycles at each loading sequence of the resilient modulus test (AASHTO T 292-91) needs to be increased significantly. Experimental data indicate that matric suctions measured in the specimen after consolidation and resilient modulus tests are consistent with the matric suctions deduced from the soil-water characteristic curve corresponding to the same moisture content. In general, the resilient modulus obtained by the suction-controlled resilient modulus test appears to be reasonable. The trends of resilient modulus obtained by the suction-controlled resilient modulus test are consistent with those obtained by the conventional resilient modulus test. However, the suction-controlled resilient modulus test provides better insights that can help in interpreting the test results. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Suction-controlled laboratory test on resilient modulus of unsaturated compacted subgrade soils [texte imprimé] / Shu-Rong Yang, Auteur ; Horn-Da Lin, Auteur ; Kung, Johnson H. S., Auteur . - 2008 . - pp. 1375–1384.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1375–1384
Mots-clés : Subgrades Soil suction Resilient modulus Laboratory tests Unsaturated soils Soil compaction Résumé : Conventionally, the resilient modulus test is conducted in the laboratory under different moisture content in which matric suction is unknown during the test. To investigate the influence of the matric suction on the resilient modulus, this study integrated the suction-controlled testing system and developed a modified testing procedure for the resilient modulus test of unsaturated subgrade soils. Based on the axis-translation technique, two cohesive soils were tested to investigate the effect of matric suction on resilient modulus. In the modified testing procedure, in order to fulfill the equilibrium in matric suction, the number of load cycles at each loading sequence of the resilient modulus test (AASHTO T 292-91) needs to be increased significantly. Experimental data indicate that matric suctions measured in the specimen after consolidation and resilient modulus tests are consistent with the matric suctions deduced from the soil-water characteristic curve corresponding to the same moisture content. In general, the resilient modulus obtained by the suction-controlled resilient modulus test appears to be reasonable. The trends of resilient modulus obtained by the suction-controlled resilient modulus test are consistent with those obtained by the conventional resilient modulus test. However, the suction-controlled resilient modulus test provides better insights that can help in interpreting the test results. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1385–1398
Titre : Multiscale modeling of flood-induced piping in river levees Type de document : texte imprimé Auteurs : El Shami, Usama, Auteur ; Firat Aydin, Auteur Année de publication : 2008 Article en page(s) : pp. 1385–1398 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Seepage Granular media Transient flow Discrete elements Soil deformation Soil-structure interaction Résumé : c change in porosity and possible occurrence of nonlinear losses. The hydraulic structure (levee) is modeled as an impervious rigid block and its motion is described by a combination of external and internal forces from the surrounding fluid and solid particles. A computational simulation is conducted to investigate the response of a granular deposit when subjected to a rapidly increasing head difference. The simulation provided information at the microscale level for the solid phase as well as at the macroscopic level for the pore-water flow. The settlement and failure mechanism of the structure were captured as the hydraulic head difference gradually increased and the solid phase underwent subsequent deformations. The results suggest that failure of such structures may occur suddenly and at hydraulic gradients well below the critical gradient. The proposed computational framework for analyzing river and flood-protection levees would provide a new dimension to the design of such vital geotechnical systems. The technique can be effectively used to investigate failure mechanisms under complex loading and flow conditions. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Multiscale modeling of flood-induced piping in river levees [texte imprimé] / El Shami, Usama, Auteur ; Firat Aydin, Auteur . - 2008 . - pp. 1385–1398.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1385–1398
Mots-clés : Seepage Granular media Transient flow Discrete elements Soil deformation Soil-structure interaction Résumé : c change in porosity and possible occurrence of nonlinear losses. The hydraulic structure (levee) is modeled as an impervious rigid block and its motion is described by a combination of external and internal forces from the surrounding fluid and solid particles. A computational simulation is conducted to investigate the response of a granular deposit when subjected to a rapidly increasing head difference. The simulation provided information at the microscale level for the solid phase as well as at the macroscopic level for the pore-water flow. The settlement and failure mechanism of the structure were captured as the hydraulic head difference gradually increased and the solid phase underwent subsequent deformations. The results suggest that failure of such structures may occur suddenly and at hydraulic gradients well below the critical gradient. The proposed computational framework for analyzing river and flood-protection levees would provide a new dimension to the design of such vital geotechnical systems. The technique can be effectively used to investigate failure mechanisms under complex loading and flow conditions. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1399–1406
Titre : Central artery/tunnel project excavation induced ground deformations Type de document : texte imprimé Auteurs : Youssef M.A. Hashash, Auteur ; Abdolreza Osouli, Auteur ; Camilo Marulanda, Auteur Année de publication : 2008 Article en page(s) : pp. 1399–1406 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Excavation Soil deformation Tunnels Urban areas Résumé : Estimate of deformations around urban excavations is a primary concern for designers, contractors, owners, and potentially affected third parties. Significant efforts have gone into the development of empirically based methods to estimate deformations relying on a large number of case histories. The construction of the deep excavations for the central artery/tunnel project provides valuable information on observed deformations due to the construction of these excavations. Lateral deformations and surface settlements for three construction contracts are collected and summarized in a form similar to published empirical charts. The stiff support system used in these braced excavation and the embedment of the wall into stiff strata control deformations to minimal levels. The data show that surface settlements, although small, extend farther away from the excavation than previously reported. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Central artery/tunnel project excavation induced ground deformations [texte imprimé] / Youssef M.A. Hashash, Auteur ; Abdolreza Osouli, Auteur ; Camilo Marulanda, Auteur . - 2008 . - pp. 1399–1406.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1399–1406
Mots-clés : Excavation Soil deformation Tunnels Urban areas Résumé : Estimate of deformations around urban excavations is a primary concern for designers, contractors, owners, and potentially affected third parties. Significant efforts have gone into the development of empirically based methods to estimate deformations relying on a large number of case histories. The construction of the deep excavations for the central artery/tunnel project provides valuable information on observed deformations due to the construction of these excavations. Lateral deformations and surface settlements for three construction contracts are collected and summarized in a form similar to published empirical charts. The stiff support system used in these braced excavation and the embedment of the wall into stiff strata control deformations to minimal levels. The data show that surface settlements, although small, extend farther away from the excavation than previously reported. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1407–1411
Titre : Discrete element modeling of contact creep and aging in sand Type de document : texte imprimé Auteurs : Yu-Hsing Wang, Auteur ; Dapeng Xu, Auteur ; King-Yuen Tsui, Auteur Année de publication : 2008 Article en page(s) : pp. 1407–1411 Note générale : Geotechnical and gzoenvironmental negineering Langues : Anglais (eng) Mots-clés : Sand Contact pressure Creep Aging Stiffness Dilatancy Résumé : In this study, aging in dry, clean sand induced by contact creep is investigated through numerical simulations using the discrete element method. Simulation results demonstrate that contact creep initiates the redistribution of contact forces. Although contact creep produces a very small decrease in porosity (approximately 1.7%), a significant change in the contact force distribution is produced in the aged sample. The contact forces ultimately become more uniform in both magnitude and spatial distribution. This homogenization of contact forces leads to more stable force chains and therefore produces an increase in the small-strain stiffness, early strength, and dilatancy in the aged sample. Such increases are not found in the sample prepared to the same porosity as the aged sample but without aging. This is because, in generating this sample, the contact creep is not allowed and therefore its associated contact force distribution is less homogenized compared with that in the aged sample. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2814 [...] [article] Discrete element modeling of contact creep and aging in sand [texte imprimé] / Yu-Hsing Wang, Auteur ; Dapeng Xu, Auteur ; King-Yuen Tsui, Auteur . - 2008 . - pp. 1407–1411.
Geotechnical and gzoenvironmental negineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1407–1411
Mots-clés : Sand Contact pressure Creep Aging Stiffness Dilatancy Résumé : In this study, aging in dry, clean sand induced by contact creep is investigated through numerical simulations using the discrete element method. Simulation results demonstrate that contact creep initiates the redistribution of contact forces. Although contact creep produces a very small decrease in porosity (approximately 1.7%), a significant change in the contact force distribution is produced in the aged sample. The contact forces ultimately become more uniform in both magnitude and spatial distribution. This homogenization of contact forces leads to more stable force chains and therefore produces an increase in the small-strain stiffness, early strength, and dilatancy in the aged sample. Such increases are not found in the sample prepared to the same porosity as the aged sample but without aging. This is because, in generating this sample, the contact creep is not allowed and therefore its associated contact force distribution is less homogenized compared with that in the aged sample. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2814 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1412–1416
Titre : Pile drag load and downdrag in a liquefaction event Type de document : texte imprimé Auteurs : Bengt H. Fellenius, Auteur ; Timothy C. Siegel, Auteur Année de publication : 2008 Article en page(s) : pp. 1412–1416 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Earthquakes Liquefaction Seismic design Piles Specifications Résumé : Sandy soils may undergo compression during liquefaction. A review of published design manuals, including the 2004 AASHTO LRFD Bridge Design Specifications, indicates that some recommendations for pile design may not represent the pile response in a manner consistent with the actual axial response of the pile during liquefaction. The actual response is discussed in light of the unified pile design method and separated between liquefaction occurring above and below the static nonliquefied neutral plane location before the liquefaction event. In the former case, the effect on the pile is minor regardless of the magnitude of liquefaction-induced settlement of the surrounding soil. In the latter case, the axial compressive load in the pile increases and additional pile settlement (downdrag) will occur when the force equilibrium is reestablished through the necessary mobilization of additional toe resistance. This means that the magnitude of the downdrag is governed by the pile toe load-movement response to the downward shift of the neutral plane. While there is a reduction in shaft resistance due to the reduction in strength within the liquefied layers, this reduction will only influence the pile design length where the liquefying layer is very thick. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2814 [...] [article] Pile drag load and downdrag in a liquefaction event [texte imprimé] / Bengt H. Fellenius, Auteur ; Timothy C. Siegel, Auteur . - 2008 . - pp. 1412–1416.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1412–1416
Mots-clés : Earthquakes Liquefaction Seismic design Piles Specifications Résumé : Sandy soils may undergo compression during liquefaction. A review of published design manuals, including the 2004 AASHTO LRFD Bridge Design Specifications, indicates that some recommendations for pile design may not represent the pile response in a manner consistent with the actual axial response of the pile during liquefaction. The actual response is discussed in light of the unified pile design method and separated between liquefaction occurring above and below the static nonliquefied neutral plane location before the liquefaction event. In the former case, the effect on the pile is minor regardless of the magnitude of liquefaction-induced settlement of the surrounding soil. In the latter case, the axial compressive load in the pile increases and additional pile settlement (downdrag) will occur when the force equilibrium is reestablished through the necessary mobilization of additional toe resistance. This means that the magnitude of the downdrag is governed by the pile toe load-movement response to the downward shift of the neutral plane. While there is a reduction in shaft resistance due to the reduction in strength within the liquefied layers, this reduction will only influence the pile design length where the liquefying layer is very thick. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2814 [...]
Exemplaires
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