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Dynamic properties of highly organic soils from montezuma slough and clifton court / Tadahiro Kishida in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 4 (Avril 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 4 (Avril 2009) . - pp. 525–532 Titre : Dynamic properties of highly organic soils from montezuma slough and clifton court Type de document : texte imprimé Auteurs : Tadahiro Kishida, Auteur ; Timothy M. Wehling, Auteur ; Ross W. Boulanger, Auteur Année de publication : 2009 Article en page(s) : pp. 525–532 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Soil  properties  Dynamic  properties  Organic  matter  Peat  Shear  modulus  Damping Résumé : The nonlinear dynamic properties of highly organic soils from two levee sites in the Sacramento-San Joaquin Delta in California are described. Cyclic triaxial, resonant column and torsional shear tests were performed on thin-walled tube samples obtained from beneath levee crests, beneath adjacent berms, and in the free field such that the in situ vertical effective stresses (σ′vo) ranged from about 16to67kPa . These highly organic soils had considerably different organic characteristics from those used in previous studies of dynamic properties. The tested samples had organic contents of 14 to 61%, initial water contents (wo) of 88 to 496%, shear wave velocities (Vs) of 20to130m∕s , and organic components that ranged from highly fibrous to highly decomposed and amorphous. Secant shear modulus (G) , normalized secant shear modulus (G∕Gmax) , and equivalent damping ratio (ξ) versus cyclic shear strain amplitude (γc) relations are presented, and their dependence on variables such as consolidation stress, organic content, prior loading history, testing device, and loading frequency are illustrated. Findings are compared to previously published results. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A4%2852 [...] [article] Dynamic properties of highly organic soils from montezuma slough and clifton court [texte imprimé] / Tadahiro Kishida, Auteur ; Timothy M. Wehling, Auteur ; Ross W. Boulanger, Auteur . - 2009 . - pp. 525–532. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 4 (Avril 2009) . - pp. 525–532 Mots-clés : Soil  properties  Dynamic  properties  Organic  matter  Peat  Shear  modulus  Damping Résumé : The nonlinear dynamic properties of highly organic soils from two levee sites in the Sacramento-San Joaquin Delta in California are described. Cyclic triaxial, resonant column and torsional shear tests were performed on thin-walled tube samples obtained from beneath levee crests, beneath adjacent berms, and in the free field such that the in situ vertical effective stresses (σ′vo) ranged from about 16to67kPa . These highly organic soils had considerably different organic characteristics from those used in previous studies of dynamic properties. The tested samples had organic contents of 14 to 61%, initial water contents (wo) of 88 to 496%, shear wave velocities (Vs) of 20to130m∕s , and organic components that ranged from highly fibrous to highly decomposed and amorphous. Secant shear modulus (G) , normalized secant shear modulus (G∕Gmax) , and equivalent damping ratio (ξ) versus cyclic shear strain amplitude (γc) relations are presented, and their dependence on variables such as consolidation stress, organic content, prior loading history, testing device, and loading frequency are illustrated. Findings are compared to previously published results. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A4%2852 [...]

Probabilistic seismic hazard analysis for maximum seismic shear stresses in soils using improved ground-motion parameters / Tadahiro Kishida in Journal of geotechnical and geoenvironmental engineering, Vol. 139 N° 2 (Février 2013) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 2 (Février 2013) . - pp. 288-297 Titre : Probabilistic seismic hazard analysis for maximum seismic shear stresses in soils using improved ground-motion parameters Type de document : texte imprimé Auteurs : Tadahiro Kishida, Auteur ; Chi-Chin Tsai, Auteur Année de publication : 2013 Article en page(s) : pp. 288-297 Note générale : geotechnique Langues : Anglais (eng) Mots-clés : seismic  design;  shear  stress;  ground  motion;  probability;  hazards;  soil  strength Résumé : Maximum seismic shear stresses (τmax) have been recognized as one of the important parameters in design practice. This study develops ground-motion parameters for τmax and implements these in probabilistic seismic hazard analysis to provide the τmax distribution of deep soil layers for design purposes. The application of improved ground-motion parameters for τmax is demonstrated at the Oakland International Airport, where a thick Young Bay Mud deposit exists under the artificial fill. Model biases in the predictive equations of seismic shear-stress reduction coefficients (rd) are evaluated by comparison with the site response analyses performed with a wide range of input ground motions. Based on these results, we introduce improved ground-motion parameters for τmax (Itau) as a linear combination of spectral accelerations, implemented in probabilistic seismic hazard analysis to calculate seismic hazard curves. Conditional mean spectra are calculated, given Itau at 10% in 50 years to illustrate the variations in frequency contents with depth compared with the uniform hazard spectra. Finally, τmax is calculated with depth by using hazard values of Itau and compared with the peak-ground-acceleration-based and uniform-hazard-spectra-based calculations. Analysis results show that τmax will be underestimated for deep soil layers by peak-ground-acceleration-based calculation if the median value of rd is used in design practice. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000740 [article] Probabilistic seismic hazard analysis for maximum seismic shear stresses in soils using improved ground-motion parameters [texte imprimé] / Tadahiro Kishida, Auteur ; Chi-Chin Tsai, Auteur . - 2013 . - pp. 288-297. geotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 2 (Février 2013) . - pp. 288-297 Mots-clés : seismic  design;  shear  stress;  ground  motion;  probability;  hazards;  soil  strength Résumé : Maximum seismic shear stresses (τmax) have been recognized as one of the important parameters in design practice. This study develops ground-motion parameters for τmax and implements these in probabilistic seismic hazard analysis to provide the τmax distribution of deep soil layers for design purposes. The application of improved ground-motion parameters for τmax is demonstrated at the Oakland International Airport, where a thick Young Bay Mud deposit exists under the artificial fill. Model biases in the predictive equations of seismic shear-stress reduction coefficients (rd) are evaluated by comparison with the site response analyses performed with a wide range of input ground motions. Based on these results, we introduce improved ground-motion parameters for τmax (Itau) as a linear combination of spectral accelerations, implemented in probabilistic seismic hazard analysis to calculate seismic hazard curves. Conditional mean spectra are calculated, given Itau at 10% in 50 years to illustrate the variations in frequency contents with depth compared with the uniform hazard spectra. Finally, τmax is calculated with depth by using hazard values of Itau and compared with the peak-ground-acceleration-based and uniform-hazard-spectra-based calculations. Analysis results show that τmax will be underestimated for deep soil layers by peak-ground-acceleration-based calculation if the median value of rd is used in design practice. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000740

Regression models for dynamic properties of highly organic soils / Tadahiro Kishida in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 4 (Avril 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 4 (Avril 2009) . - pp. 533–543 Titre : Regression models for dynamic properties of highly organic soils Type de document : texte imprimé Auteurs : Tadahiro Kishida, Auteur ; Ross W. Boulanger, Auteur ; Abrahamson, Norman A., Auteur Année de publication : 2009 Article en page(s) : pp. 533–543 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Soil  properties  Dynamic  properties  Organic  matter  Peat  Shear  modulus  Damping  Regression  models Résumé : Regression models are presented for the dynamic properties of highly organic soils. The models are based on a database of triaxial and resonant-column/torsional-shear cyclic loading tests on thin walled tube samples mainly retrieved from the Sacramento-San Joaquin Delta. The soils in this database range from highly fibrous peat to amorphous organic clays with organic contents (OC) ranging from 14–81%, water contents ranging from 88–495%, total densities (ρ) ranging from 1.056–1.450Mg/m3 , and effective consolidation stresses (σ′vc) ranging from 11–135kPa . The secant shear modulus (G) and equivalent damping ratio (ξ) were modeled as variables dependent on the shear strain amplitude (γc) , consolidation stress (σ′vc) , and OC. The residuals of the regression models were analyzed against other predictor variables including undisturbed density (ρ) , loading frequency (f) , and number of loading cycles (N) . A regression model for ρ was developed, and conditional probabilities were used to improve the estimation of G and ξ when ρ measurements were available. The database of in situ measurements of shear wave velocity (Vs) was used to adjust the regression model for in situ conditions. Variances and correlations in the regression models are presented. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A4%2853 [...] [article] Regression models for dynamic properties of highly organic soils [texte imprimé] / Tadahiro Kishida, Auteur ; Ross W. Boulanger, Auteur ; Abrahamson, Norman A., Auteur . - 2009 . - pp. 533–543. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 4 (Avril 2009) . - pp. 533–543 Mots-clés : Soil  properties  Dynamic  properties  Organic  matter  Peat  Shear  modulus  Damping  Regression  models Résumé : Regression models are presented for the dynamic properties of highly organic soils. The models are based on a database of triaxial and resonant-column/torsional-shear cyclic loading tests on thin walled tube samples mainly retrieved from the Sacramento-San Joaquin Delta. The soils in this database range from highly fibrous peat to amorphous organic clays with organic contents (OC) ranging from 14–81%, water contents ranging from 88–495%, total densities (ρ) ranging from 1.056–1.450Mg/m3 , and effective consolidation stresses (σ′vc) ranging from 11–135kPa . The secant shear modulus (G) and equivalent damping ratio (ξ) were modeled as variables dependent on the shear strain amplitude (γc) , consolidation stress (σ′vc) , and OC. The residuals of the regression models were analyzed against other predictor variables including undisturbed density (ρ) , loading frequency (f) , and number of loading cycles (N) . A regression model for ρ was developed, and conditional probabilities were used to improve the estimation of G and ξ when ρ measurements were available. The database of in situ measurements of shear wave velocity (Vs) was used to adjust the regression model for in situ conditions. Variances and correlations in the regression models are presented. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A4%2853 [...]