Documents disponibles écrits par cet auteur

Effect of uniformity coefficient on G/Gmax and damping ratio of uniform to well-graded quartz sands / T. Wichtmann in Journal of geotechnical and geoenvironmental engineering, Vol. 139 N° 1 (Janvier 2013) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 1 (Janvier 2013) . - pp. 59-72 Titre : Effect of uniformity coefficient on G/Gmax and damping ratio of uniform to well-graded quartz sands Type de document : texte imprimé Auteurs : T. Wichtmann, Auteur ; T. Triantafyllidis, Auteur Année de publication : 2013 Article en page(s) : pp. 59-72 Note générale : geotechnique Langues : Anglais (eng) Mots-clés : shear  modulus;  damping  ratio;  quartz  sand;  grain  size  distribution  curve;  uniformity  coefficient;  resonant  column  tests Résumé : The modulus degradation curves, G(γ)/Gmax, and the damping ratio, D(γ), of 27 clean quartz sands with specially mixed grain size distribution curves were measured in approximately 280 resonant column tests. For each material, tests with various pressures and densities were performed. Based on the test data it is demonstrated that the shear modulus degradation is larger for higher values of the uniformity coefficient, Cu=d60/d10, while it is rather independent of the mean grain size, d50. The observed Cu dependence of curves G(γ)/Gmax is not adequately described by common empirical equations because these equations were developed based on tests on uniform granular materials. To consider the influence of the uniformity coefficient, the paper proposes correlations of the parameters of the common empirical equations with Cu. Good agreement between the prediction of the extended empirical equations and the experimental data collected from the literature is demonstrated. Furthermore, the test data reveal that the curves of damping ratio, D(γ), and the threshold shear strain amplitude indicating the onset of residual deformation accumulation, γtv, are rather independent of d50 and Cu. The threshold shear strain amplitude at the onset of modulus degradation, γtl, slightly decreases with increasing values of d50 and Cu. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000735 [article] Effect of uniformity coefficient on G/Gmax and damping ratio of uniform to well-graded quartz sands [texte imprimé] / T. Wichtmann, Auteur ; T. Triantafyllidis, Auteur . - 2013 . - pp. 59-72. geotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 1 (Janvier 2013) . - pp. 59-72 Mots-clés : shear  modulus;  damping  ratio;  quartz  sand;  grain  size  distribution  curve;  uniformity  coefficient;  resonant  column  tests Résumé : The modulus degradation curves, G(γ)/Gmax, and the damping ratio, D(γ), of 27 clean quartz sands with specially mixed grain size distribution curves were measured in approximately 280 resonant column tests. For each material, tests with various pressures and densities were performed. Based on the test data it is demonstrated that the shear modulus degradation is larger for higher values of the uniformity coefficient, Cu=d60/d10, while it is rather independent of the mean grain size, d50. The observed Cu dependence of curves G(γ)/Gmax is not adequately described by common empirical equations because these equations were developed based on tests on uniform granular materials. To consider the influence of the uniformity coefficient, the paper proposes correlations of the parameters of the common empirical equations with Cu. Good agreement between the prediction of the extended empirical equations and the experimental data collected from the literature is demonstrated. Furthermore, the test data reveal that the curves of damping ratio, D(γ), and the threshold shear strain amplitude indicating the onset of residual deformation accumulation, γtv, are rather independent of d50 and Cu. The threshold shear strain amplitude at the onset of modulus degradation, γtl, slightly decreases with increasing values of d50 and Cu. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000735

Influence of the grain-size distribution curve of quartz sand on the small strain shear modulus Gmax / T. Wichtmann in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 10 (Octobre 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 10 (Octobre 2009) . - pp. 1404–1418 Titre : Influence of the grain-size distribution curve of quartz sand on the small strain shear modulus Gmax Type de document : texte imprimé Auteurs : T. Wichtmann, Auteur ; T. Triantafyllidis, Auteur Année de publication : 2009 Article en page(s) : pp. 1404–1418 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Shear  modulusSandCoefficientsGrain  sizeStrain Résumé : The paper presents a study of the influence of grain-size distribution curve on the small strain shear modulus Gmax of quartz sand with subangular grain shape. The results of 163 resonant column tests on 25 different grain-size distribution curves are presented. It is demonstrated for a constant void ratio that while Gmax is not influenced by variations in the mean grain-size d50 in the investigated range, it significantly decreases with increasing coefficient of uniformity Cu=d60/d10 of the grain-size distribution curve. Well-known empirical formulas (e.g., Hardin’s equation with its commonly used constants) may strongly overestimate the stiffness of well-graded soils. Based on the RC test results, correlations of the constants of Hardin’s equation with Cu have been developed. The predictions using Hardin’s equation and these correlations are in good accordance with the test data. Correlations of the frequently used shear modulus coefficient K2,max with Cu and empirical equations formulated in terms of relative density, are also given in the paper. A comparison of the predictions by the proposed empirical formulas with Gmax -data from the literature and a micromechanical explanation of the experimental results are provided. Correction factors for an application of the laboratory data to in situ conditions are also discussed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000096 [article] Influence of the grain-size distribution curve of quartz sand on the small strain shear modulus Gmax [texte imprimé] / T. Wichtmann, Auteur ; T. Triantafyllidis, Auteur . - 2009 . - pp. 1404–1418. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 10 (Octobre 2009) . - pp. 1404–1418 Mots-clés : Shear  modulusSandCoefficientsGrain  sizeStrain Résumé : The paper presents a study of the influence of grain-size distribution curve on the small strain shear modulus Gmax of quartz sand with subangular grain shape. The results of 163 resonant column tests on 25 different grain-size distribution curves are presented. It is demonstrated for a constant void ratio that while Gmax is not influenced by variations in the mean grain-size d50 in the investigated range, it significantly decreases with increasing coefficient of uniformity Cu=d60/d10 of the grain-size distribution curve. Well-known empirical formulas (e.g., Hardin’s equation with its commonly used constants) may strongly overestimate the stiffness of well-graded soils. Based on the RC test results, correlations of the constants of Hardin’s equation with Cu have been developed. The predictions using Hardin’s equation and these correlations are in good accordance with the test data. Correlations of the frequently used shear modulus coefficient K2,max with Cu and empirical equations formulated in terms of relative density, are also given in the paper. A comparison of the predictions by the proposed empirical formulas with Gmax -data from the literature and a micromechanical explanation of the experimental results are provided. Correction factors for an application of the laboratory data to in situ conditions are also discussed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000096