Documents disponibles écrits par cet auteur

Blast densification / Guillermo A. Narsilio in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 6 (Juin 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 6 (Juin 2009) . - pp. 723–734 Titre : Blast densification : multi-instrumented case history Type de document : texte imprimé Auteurs : Guillermo A. Narsilio, Auteur ; J. Carlos Santamarina, Auteur ; Tamara Hebeler, Auteur Année de publication : 2009 Article en page(s) : pp. 723–734 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Blasting  Soil  stabilization  Settlement  Measurement  Soil  liquefaction  South  Carolina Résumé : A comprehensive blast densification field study was conducted at a test site in South Carolina to densify a loose soil layer at a depth between z=8–13m . The study included extensive laboratory and field characterizations and four carefully monitored blast events. Results revealed that densification is not an instantaneous phenomenon; underlying time-dependent processes involve resedimentation, drainage of excess pore pressure as the granular skeleton deforms and the effective stress recovers, and secondary settlement effects, which do not involve excess pore pressure dissipation. The degree of densification decreased in successive blasting events, and the soil gradually evolved toward an asymptotical terminal density associated with blast densification. The blasting sequence and detonation delays appeared to have a minor effect on shear-induced movements. The increase in penetration resistance manifested 2years after four blasting-drainage events. Instead, surface settlement using standard surveying techniques, subsurface deformation assessment, and subsurface pore fluid pressure monitoring provided valuable, real-time indicators of the soil response to the blasting events. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000023 [article] Blast densification : multi-instrumented case history [texte imprimé] / Guillermo A. Narsilio, Auteur ; J. Carlos Santamarina, Auteur ; Tamara Hebeler, Auteur . - 2009 . - pp. 723–734. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 6 (Juin 2009) . - pp. 723–734 Mots-clés : Blasting  Soil  stabilization  Settlement  Measurement  Soil  liquefaction  South  Carolina Résumé : A comprehensive blast densification field study was conducted at a test site in South Carolina to densify a loose soil layer at a depth between z=8–13m . The study included extensive laboratory and field characterizations and four carefully monitored blast events. Results revealed that densification is not an instantaneous phenomenon; underlying time-dependent processes involve resedimentation, drainage of excess pore pressure as the granular skeleton deforms and the effective stress recovers, and secondary settlement effects, which do not involve excess pore pressure dissipation. The degree of densification decreased in successive blasting events, and the soil gradually evolved toward an asymptotical terminal density associated with blast densification. The blasting sequence and detonation delays appeared to have a minor effect on shear-induced movements. The increase in penetration resistance manifested 2years after four blasting-drainage events. Instead, surface settlement using standard surveying techniques, subsurface deformation assessment, and subsurface pore fluid pressure monitoring provided valuable, real-time indicators of the soil response to the blasting events. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000023

Mechanical effects of biogenic nitrogen gas bubbles in soils / Veronica Rebata-Landa in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 2 (Fevrier 2012) . - pp. 128-137 Titre : Mechanical effects of biogenic nitrogen gas bubbles in soils Type de document : texte imprimé Auteurs : Veronica Rebata-Landa, Auteur ; J. Carlos Santamarina, Auteur Année de publication : 2012 Article en page(s) : pp. 128-137 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Bulk  Stiffness  Undrained  strength  Biogenic  gas  Gas  bubbles  PP-wave  velocity Résumé : The fluid bulk stiffness of a soil is very sensitive to the presence of gas, and a small volume of bubbles can significantly affect the pore pressure response to loading, including Skempton’s B parameter, P-wave velocity, and liquefaction resistance. Biologically mediated processes can lead to the production of gases in soils; nitrogen is particularly advantageous because it is not a greenhouse gas, it is not combustible, and it has low solubility in water. Sands, silts, and clayey sands inoculated with Paracoccus denitrificans were monitored to assess the effects of nutrient availability, fines content, and pressure-diffusion on the evolution of nitrogen gas generation and bulk stiffness. Results show clear evidence of biogas bubble formation, earlier gas generation and entrapment in specimens with higher fines content, and a strong correlation between biogas volume and P-wave velocity. The volume of gas is correlated with specific surface, suggesting that biogas bubble formation develops as heterogeneous nucleation and that it is directly linked to the availability of nucleation sites on mineral surfaces, which in turn also affect the degree of attainable supersaturation. Results support the viability of biogenic gas generation as a tool to increase the liquefaction resistance of soils subjected to cyclic loading. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i2/p128_s1?isAuthorized=no [article] Mechanical effects of biogenic nitrogen gas bubbles in soils [texte imprimé] / Veronica Rebata-Landa, Auteur ; J. Carlos Santamarina, Auteur . - 2012 . - pp. 128-137. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 2 (Fevrier 2012) . - pp. 128-137 Mots-clés : Bulk  Stiffness  Undrained  strength  Biogenic  gas  Gas  bubbles  PP-wave  velocity Résumé : The fluid bulk stiffness of a soil is very sensitive to the presence of gas, and a small volume of bubbles can significantly affect the pore pressure response to loading, including Skempton’s B parameter, P-wave velocity, and liquefaction resistance. Biologically mediated processes can lead to the production of gases in soils; nitrogen is particularly advantageous because it is not a greenhouse gas, it is not combustible, and it has low solubility in water. Sands, silts, and clayey sands inoculated with Paracoccus denitrificans were monitored to assess the effects of nutrient availability, fines content, and pressure-diffusion on the evolution of nitrogen gas generation and bulk stiffness. Results show clear evidence of biogas bubble formation, earlier gas generation and entrapment in specimens with higher fines content, and a strong correlation between biogas volume and P-wave velocity. The volume of gas is correlated with specific surface, suggesting that biogas bubble formation develops as heterogeneous nucleation and that it is directly linked to the availability of nucleation sites on mineral surfaces, which in turn also affect the degree of attainable supersaturation. Results support the viability of biogenic gas generation as a tool to increase the liquefaction resistance of soils subjected to cyclic loading. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i2/p128_s1?isAuthorized=no

Mineral dissolution and the evolution of k0 / Hosung Shin in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 8 (Août 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 8 (Août 2009) . - pp. 1141–1147 Titre : Mineral dissolution and the evolution of k0 Type de document : texte imprimé Auteurs : Hosung Shin, Auteur ; J. Carlos Santamarina, Auteur Année de publication : 2009 Article en page(s) : pp. 1141–1147 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Soil  structures  Stress  Minerals Résumé : Adequate knowledge of the in situ state of stress can be essential to the analysis of geotechnical systems. However, the measurement and prediction of k0 remain difficult. In particular, limited attention has been given to the evolution of k0 during the formation history of the soil and diagenetic processes such as mineral dissolution. Experimental and numerical results show that grain mass loss due to mineral dissolution produces a pronounced horizontal stress drop under zero lateral strain conditions; the state of stress may reach the active shear failure ka condition and internal shear planes may develop. While horizontal stress recovery often follows upon further dissolution, marked differences in fabric are observed between the pre and postdissolution soil structures. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000053 [article] Mineral dissolution and the evolution of k0 [texte imprimé] / Hosung Shin, Auteur ; J. Carlos Santamarina, Auteur . - 2009 . - pp. 1141–1147. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 8 (Août 2009) . - pp. 1141–1147 Mots-clés : Soil  structures  Stress  Minerals Résumé : Adequate knowledge of the in situ state of stress can be essential to the analysis of geotechnical systems. However, the measurement and prediction of k0 remain difficult. In particular, limited attention has been given to the evolution of k0 during the formation history of the soil and diagenetic processes such as mineral dissolution. Experimental and numerical results show that grain mass loss due to mineral dissolution produces a pronounced horizontal stress drop under zero lateral strain conditions; the state of stress may reach the active shear failure ka condition and internal shear planes may develop. While horizontal stress recovery often follows upon further dissolution, marked differences in fabric are observed between the pre and postdissolution soil structures. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000053

Strain-rate effects in Mexico city soil / J. Abraham Díaz-Rodríguez in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N°2 (Février 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°2 (Février 2009) . - pp. 300–305 Titre : Strain-rate effects in Mexico city soil Type de document : texte imprimé Auteurs : J. Abraham Díaz-Rodríguez, Auteur ; J. José Martínez-Vasquez, Auteur ; J. Carlos Santamarina, Auteur Année de publication : 2009 Article en page(s) : pp. 300–305 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Undisturbed  soils  Soil  structures  Strain  rate  Deposition  Triaxial  compression  Strength  Mexico Résumé : Mexico City soil has very high specific surface, plasticity and void ratio; its natural structure is preserved until the yield pressure σ′y , which is typically above the in situ effective stress σ′v , and the mechanical response changes significantly when the effective confining stress σ′o exceeds the yield pressure σ′y . In this study, the effects of strain rate on the undrained response of Mexico City soil are explored using undisturbed specimens subjected to monotonic triaxial compression tests at a constant rate of deformation. Results show that strain-rate effects on undrained strength and mode of failure depend on σ′y/σ′o , hence, on the degree of natural structure preserved in the specimen. Undrained strength increase with strain rate, particularly in the more structured specimens (i.e., higher σ′y/σ′o ). The role of σ′y/σ′o on strain-rate effects in this unremolded natural soil resembles the effect of overconsolidation ratio on resedimented specimens. The limitations in using standard triaxial equipment for strain-rate effect studies are discussed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A2%2830 [...] [article] Strain-rate effects in Mexico city soil [texte imprimé] / J. Abraham Díaz-Rodríguez, Auteur ; J. José Martínez-Vasquez, Auteur ; J. Carlos Santamarina, Auteur . - 2009 . - pp. 300–305. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°2 (Février 2009) . - pp. 300–305 Mots-clés : Undisturbed  soils  Soil  structures  Strain  rate  Deposition  Triaxial  compression  Strength  Mexico Résumé : Mexico City soil has very high specific surface, plasticity and void ratio; its natural structure is preserved until the yield pressure σ′y , which is typically above the in situ effective stress σ′v , and the mechanical response changes significantly when the effective confining stress σ′o exceeds the yield pressure σ′y . In this study, the effects of strain rate on the undrained response of Mexico City soil are explored using undisturbed specimens subjected to monotonic triaxial compression tests at a constant rate of deformation. Results show that strain-rate effects on undrained strength and mode of failure depend on σ′y/σ′o , hence, on the degree of natural structure preserved in the specimen. Undrained strength increase with strain rate, particularly in the more structured specimens (i.e., higher σ′y/σ′o ). The role of σ′y/σ′o on strain-rate effects in this unremolded natural soil resembles the effect of overconsolidation ratio on resedimented specimens. The limitations in using standard triaxial equipment for strain-rate effect studies are discussed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A2%2830 [...]