Documents disponibles écrits par cet auteur

Complementary wave-based characterizations of sedimentation processes / Yu-Hsing Wang in Journal of geotechnical and geoenvironmental engineering, Vol. 134 N°1 (Janvier 2008) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°1 (Janvier 2008) . - pp. 47–56 Titre : Complementary wave-based characterizations of sedimentation processes Type de document : texte imprimé Auteurs : Yu-Hsing Wang, Auteur ; Xiaobo Dong, Auteur Année de publication : 2008 Article en page(s) : pp. 47–56 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Shear  waves  Clays  Anisotropy  Sedimentation  Fabrics Résumé : In this paper, the sedimentation behavior of two kaolinite samples with distinct fabric associations is characterized using mechanical and electromagnetic wave-based techniques. The two different fabric formations, the edge-to-face (EF) flocculated structure (i.e., Sample A) and the dispersed and deflocculated structure (i.e., Sample B), were produced by changing the pH of the pore fluid. The anisotropy of the shear-wave velocity and DC conductivity was not observed in the sediment of Sample A because of EF isotropic fabric associations, but it was detected in Sample B as a result of face-to-face aggregation. An open card-house structure of the Sample A sediment results in a higher relaxation strength of the bulk water, Δκw owing to a higher water content; the smaller Δκw measured in the Sample B sediment indicates denser packing. In both samples, sediment consolidation gives rise to a decrease in the bulk-water relaxation strength, but an increase in the bound-water relaxation strength owing to increasing particle content. During sediment consolidation, the sediment conductivity of Sample A continuously decreases because of the reduced contribution from the fluid conductivity. In Sample B, the surface conduction overcompensates such a decreased contribution so that the sediment conductivity increases with increasing particle content. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A1%2847 [...] [article] Complementary wave-based characterizations of sedimentation processes [texte imprimé] / Yu-Hsing Wang, Auteur ; Xiaobo Dong, Auteur . - 2008 . - pp. 47–56. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°1 (Janvier 2008) . - pp. 47–56 Mots-clés : Shear  waves  Clays  Anisotropy  Sedimentation  Fabrics Résumé : In this paper, the sedimentation behavior of two kaolinite samples with distinct fabric associations is characterized using mechanical and electromagnetic wave-based techniques. The two different fabric formations, the edge-to-face (EF) flocculated structure (i.e., Sample A) and the dispersed and deflocculated structure (i.e., Sample B), were produced by changing the pH of the pore fluid. The anisotropy of the shear-wave velocity and DC conductivity was not observed in the sediment of Sample A because of EF isotropic fabric associations, but it was detected in Sample B as a result of face-to-face aggregation. An open card-house structure of the Sample A sediment results in a higher relaxation strength of the bulk water, Δκw owing to a higher water content; the smaller Δκw measured in the Sample B sediment indicates denser packing. In both samples, sediment consolidation gives rise to a decrease in the bulk-water relaxation strength, but an increase in the bound-water relaxation strength owing to increasing particle content. During sediment consolidation, the sediment conductivity of Sample A continuously decreases because of the reduced contribution from the fluid conductivity. In Sample B, the surface conduction overcompensates such a decreased contribution so that the sediment conductivity increases with increasing particle content. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A1%2847 [...]

Discrete element modeling of contact creep and aging in sand / Yu-Hsing Wang in Journal of geotechnical and geoenvironmental engineering, Vol. 134 n°9 (Septembre 2008) 

Public ISBD [article]  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 [...]

Experimental characterization of dynamic property changes in aged sands / Yu-Hsing Wang 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. 259–270 Titre : Experimental characterization of dynamic property changes in aged sands Type de document : texte imprimé Auteurs : Yu-Hsing Wang, Auteur ; King-Yuen Tsui, Auteur Année de publication : 2009 Article en page(s) : pp. 259–270 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Sand  Aging  Shear  modulus  Damping  Creep Résumé : This study investigates the aging effects on the small-strain shear modulus and damping ratio of sands and offers explanations for the measured results based on the concept of contact-force homogenization. Resonant column tests of aged sands under various aging conditions were conducted. The results show that loose sands exhibit greater aging effects than dense sands do at a confining pressure of 35kPa and the effects are completely opposite when the aging pressure is increased to 100kPa . The aging effects can be partially erased by unloading-reloading; the remaining effects can be restored when the applied pressure is the same as the original pressure used during aging and cannot be further erased by additional unloading-reloading cycles. The stress history is also a factor that affects aging behavior: unloading reloading and overconsolidation can reduce the aging rate in terms of the shear-modulus increase. The aging effects, however, can be wiped out by large strain shearing. An addition of fines (dry kaolinite powder) in the sand samples can increase the aging rate because of higher creep made by the kaolinite. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A2%2825 [...] [article] Experimental characterization of dynamic property changes in aged sands [texte imprimé] / Yu-Hsing Wang, Auteur ; King-Yuen Tsui, Auteur . - 2009 . - pp. 259–270. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°2 (Février 2009) . - pp. 259–270 Mots-clés : Sand  Aging  Shear  modulus  Damping  Creep Résumé : This study investigates the aging effects on the small-strain shear modulus and damping ratio of sands and offers explanations for the measured results based on the concept of contact-force homogenization. Resonant column tests of aged sands under various aging conditions were conducted. The results show that loose sands exhibit greater aging effects than dense sands do at a confining pressure of 35kPa and the effects are completely opposite when the aging pressure is increased to 100kPa . The aging effects can be partially erased by unloading-reloading; the remaining effects can be restored when the applied pressure is the same as the original pressure used during aging and cannot be further erased by additional unloading-reloading cycles. The stress history is also a factor that affects aging behavior: unloading reloading and overconsolidation can reduce the aging rate in terms of the shear-modulus increase. The aging effects, however, can be wiped out by large strain shearing. An addition of fines (dry kaolinite powder) in the sand samples can increase the aging rate because of higher creep made by the kaolinite. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A2%2825 [...]

Mechanisms of aging-induced modulus changes in sand under isotropic and anisotropic loading / Gao, Yan in Journal of geotechnical and geoenvironmental engineering, Vol. 139 N° 3 (Mars 2013) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 3 (Mars 2013) . - pp. 470-482 Titre : Mechanisms of aging-induced modulus changes in sand under isotropic and anisotropic loading Type de document : texte imprimé Auteurs : Gao, Yan, Auteur ; Yu-Hsing Wang, Auteur ; Jack C. P. Su, Auteur Année de publication : 2013 Article en page(s) : pp. 470-482 Note générale : geotechnique Langues : Anglais (eng) Mots-clés : aging  (material);  shear  modulus;  bending;  isotropy;  sand  (soil  type);  anisotropy Résumé : In this paper, experimental studies were conducted using a true triaxial apparatus with a bender element system to examine the mechanisms of aging-induced, small-strain shear modulus changes in sand samples under isotropic and anisotropic loading. Numerical simulations based on the discrete element method (DEM) were also carried out in parallel. In the isotropic loading cases, the three measured shear moduli, Gxy, Gyz, and Gzx, and associated aging rates, in terms of the modulus changes, are similar in every loading stage. DEM simulations reproduced the experimental findings and suggested a general trend. A sample with a lower shear modulus before aging, because of a greater percentage of weak forces, allows more forces to be redistributed from the strong force network to the weak force network through the process of contact force homogenization during aging and therefore can have a higher aging rate. In the anisotropic loading cases where σz>σx=σy, the measured modulus increase (i.e., the aging rate) is greater in Gyz (or Gzx) than in Gxy. This behavior can be attributed to the increase in both the strong and weak forces in the z-direction during aging, because of arching breakdowns. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000772 [article] Mechanisms of aging-induced modulus changes in sand under isotropic and anisotropic loading [texte imprimé] / Gao, Yan, Auteur ; Yu-Hsing Wang, Auteur ; Jack C. P. Su, Auteur . - 2013 . - pp. 470-482. geotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 3 (Mars 2013) . - pp. 470-482 Mots-clés : aging  (material);  shear  modulus;  bending;  isotropy;  sand  (soil  type);  anisotropy Résumé : In this paper, experimental studies were conducted using a true triaxial apparatus with a bender element system to examine the mechanisms of aging-induced, small-strain shear modulus changes in sand samples under isotropic and anisotropic loading. Numerical simulations based on the discrete element method (DEM) were also carried out in parallel. In the isotropic loading cases, the three measured shear moduli, Gxy, Gyz, and Gzx, and associated aging rates, in terms of the modulus changes, are similar in every loading stage. DEM simulations reproduced the experimental findings and suggested a general trend. A sample with a lower shear modulus before aging, because of a greater percentage of weak forces, allows more forces to be redistributed from the strong force network to the weak force network through the process of contact force homogenization during aging and therefore can have a higher aging rate. In the anisotropic loading cases where σz>σx=σy, the measured modulus increase (i.e., the aging rate) is greater in Gyz (or Gzx) than in Gxy. This behavior can be attributed to the increase in both the strong and weak forces in the z-direction during aging, because of arching breakdowns. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000772