Measurements of drying and wetting permeability functions using a new stress-controllable soil column / C. W.W. Ng in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 1 (Janvier 2012)  

Public ISBD [article]  inJournal of geotechnical and geoenvironmental engineering > Vol. 138 N° 1 (Janvier 2012) . - pp. 58-68 Titre : Measurements of drying and wetting permeability functions using a new stress-controllable soil column Type de document : texte imprimé Auteurs : C. W.W. Ng, Auteur ; A. K. Leung, Auteur Année de publication : 2012 Article en page(s) : pp. 58-68 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Permeability function Soil-water characteristic curve Matric suction Net normal stress Stress-controllable soil column Instantaneous profile method Résumé : Direct measurement of a permeability function, k(ψ) (where ψ = suction), of an unsaturated soil is often tedious and time-consuming. Thus, researchers have proposed various semiempirical predictive methods to determine k(ψ) indirectly from a soil-water characteristic curve (SWCC) or a particle-size distribution. Also, stress effects on k(ψ) are generally not considered. To explore any stress effect on k(ψ), a new 1-m-high stress-controllable soil column is developed to measure stress-dependent SWCC (SDSWCC) and k(ψ) of soils directly. The objectives of this paper are to investigate the effects of (1) two stress-state variables (matric suction and net normal stress) and (2) a drying-wetting cycle on both SDSWCC and k(ψ) of a compacted decomposed silty clay. Each compacted soil column is subjected to an evaporation-ponding cycle under various vertical net normal stresses. The variations of pore-water pressure and volumetric water content (VWC, θw) profiles with time are measured instantaneously. The k(ψ) is hence determined by using the instantaneous profile method. At a given average vertical net normal stress, the measured k(ψ) exhibits a remarkable hysteresis loop, whereas the k(θw) seems to be less hysteretic. The effects of the vertical net normal stress appear to be more pronounced than that of the drying-wetting cycle on k(θw). As average vertical net normal stress is increased from 4 to 78 kPa, the measured permeability decreases by up to two orders of magnitude at a given VWC. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i1/p58_s1?isAuthorized=no [article] Measurements of drying and wetting permeability functions using a new stress-controllable soil column [texte imprimé] / C. W.W. Ng, Auteur ; A. K. Leung, Auteur . - 2012 . - pp. 58-68. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 1 (Janvier 2012) . - pp. 58-68 Mots-clés : Permeability function Soil-water characteristic curve Matric suction Net normal stress Stress-controllable soil column Instantaneous profile method Résumé : Direct measurement of a permeability function, k(ψ) (where ψ = suction), of an unsaturated soil is often tedious and time-consuming. Thus, researchers have proposed various semiempirical predictive methods to determine k(ψ) indirectly from a soil-water characteristic curve (SWCC) or a particle-size distribution. Also, stress effects on k(ψ) are generally not considered. To explore any stress effect on k(ψ), a new 1-m-high stress-controllable soil column is developed to measure stress-dependent SWCC (SDSWCC) and k(ψ) of soils directly. The objectives of this paper are to investigate the effects of (1) two stress-state variables (matric suction and net normal stress) and (2) a drying-wetting cycle on both SDSWCC and k(ψ) of a compacted decomposed silty clay. Each compacted soil column is subjected to an evaporation-ponding cycle under various vertical net normal stresses. The variations of pore-water pressure and volumetric water content (VWC, θw) profiles with time are measured instantaneously. The k(ψ) is hence determined by using the instantaneous profile method. At a given average vertical net normal stress, the measured k(ψ) exhibits a remarkable hysteresis loop, whereas the k(θw) seems to be less hysteretic. The effects of the vertical net normal stress appear to be more pronounced than that of the drying-wetting cycle on k(θw). As average vertical net normal stress is increased from 4 to 78 kPa, the measured permeability decreases by up to two orders of magnitude at a given VWC. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i1/p58_s1?isAuthorized=no

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