Documents disponibles écrits par cet auteur

Geotechnical properties of cemented sands in steep slopes / Brian D. Collins 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. 1359–1366 Titre : Geotechnical properties of cemented sands in steep slopes Type de document : texte imprimé Auteurs : Brian D. Collins, Auteur ; Sitar, Nicholas, Auteur Année de publication : 2009 Article en page(s) : pp. 1359–1366 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : SandSoil  cementSlope  stabilityTriaxial  testsCliffsSoil  properties Résumé : An investigation into the geotechnical properties specific to assessing the stability of weakly and moderately cemented sand cliffs is presented. A case study from eroding coastal cliffs located in central California provides both the data and impetus for this study. Herein, weakly cemented sand is defined as having an unconfined compressive strength (UCS) of less than 100 kPa, and moderately cemented sand is defined as having UCS between 100 and 400 kPa. Testing shows that both materials fail in a brittle fashion and can be modeled effectively using linear Mohr-Coulomb strength parameters, although for weakly cemented sands, curvature of the failure envelope is more evident with decreasing friction and increasing cohesion at higher confinement. Triaxial tests performed to simulate the evolving stress state of an eroding cliff, using a reduction in confinement-type stress path, result in an order of magnitude decrease in strain at failure and a more brittle response. Tests aimed at examining the influence of wetting on steep slopes show that a 60% decrease in UCS, a 50% drop in cohesion, and 80% decrease in the tensile strength occurs in moderately cemented sand upon introduction to water. In weakly cemented sands, all compressive, cohesive, and tensile strength is lost upon wetting and saturation. The results indicate that particular attention must be given to the relative level of cementation, the effects of groundwater or surficial seepage, and the small-scale strain response when performing geotechnical slope stability analyses on these materials. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000094 [article] Geotechnical properties of cemented sands in steep slopes [texte imprimé] / Brian D. Collins, Auteur ; Sitar, Nicholas, Auteur . - 2009 . - pp. 1359–1366. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 10 (Octobre 2009) . - pp. 1359–1366 Mots-clés : SandSoil  cementSlope  stabilityTriaxial  testsCliffsSoil  properties Résumé : An investigation into the geotechnical properties specific to assessing the stability of weakly and moderately cemented sand cliffs is presented. A case study from eroding coastal cliffs located in central California provides both the data and impetus for this study. Herein, weakly cemented sand is defined as having an unconfined compressive strength (UCS) of less than 100 kPa, and moderately cemented sand is defined as having UCS between 100 and 400 kPa. Testing shows that both materials fail in a brittle fashion and can be modeled effectively using linear Mohr-Coulomb strength parameters, although for weakly cemented sands, curvature of the failure envelope is more evident with decreasing friction and increasing cohesion at higher confinement. Triaxial tests performed to simulate the evolving stress state of an eroding cliff, using a reduction in confinement-type stress path, result in an order of magnitude decrease in strain at failure and a more brittle response. Tests aimed at examining the influence of wetting on steep slopes show that a 60% decrease in UCS, a 50% drop in cohesion, and 80% decrease in the tensile strength occurs in moderately cemented sand upon introduction to water. In weakly cemented sands, all compressive, cohesive, and tensile strength is lost upon wetting and saturation. The results indicate that particular attention must be given to the relative level of cementation, the effects of groundwater or surficial seepage, and the small-scale strain response when performing geotechnical slope stability analyses on these materials. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000094

Hysteresis of unsaturated hydromechanical properties of a silty soil / Ning Lu 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. 507-510 Titre : Hysteresis of unsaturated hydromechanical properties of a silty soil Type de document : texte imprimé Auteurs : Ning Lu, Auteur ; Murat Kaya, Auteur ; Brian D. Collins, Auteur Année de publication : 2013 Article en page(s) : pp. 507-510 Note générale : geotechnique Langues : Anglais (eng) Mots-clés : unsaturated  soils;  soil  suction;  hydraulic  conductivity;  soil  water;  hysteresis;  silts;  mechanical  properties Résumé : Laboratory tests to examine hysteresis in the hydrologic and mechanical properties of partially saturated soils were conducted on six intact specimens collected from a landslide-prone area of Alameda County, California. The results reveal that the pore-size distribution parameter remains statistically unchanged between the wetting and drying paths; however, the wetting or drying state has a pronounced influence on the water-entry pressure, the water-filled porosity at zero suction, and the saturated hydraulic conductivity. The suction stress values obtained from the shear-strength tests under both natural moisture and resaturated conditions were mostly bounded by the suction stress characteristic curves (SSCCs) obtained from the hydrologic tests. This finding experimentally confirms that the soil-water retention curve, hydraulic conductivity function, and SSCC are intrinsically related. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000786 [article] Hysteresis of unsaturated hydromechanical properties of a silty soil [texte imprimé] / Ning Lu, Auteur ; Murat Kaya, Auteur ; Brian D. Collins, Auteur . - 2013 . - pp. 507-510. geotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 3 (Mars 2013) . - pp. 507-510 Mots-clés : unsaturated  soils;  soil  suction;  hydraulic  conductivity;  soil  water;  hysteresis;  silts;  mechanical  properties Résumé : Laboratory tests to examine hysteresis in the hydrologic and mechanical properties of partially saturated soils were conducted on six intact specimens collected from a landslide-prone area of Alameda County, California. The results reveal that the pore-size distribution parameter remains statistically unchanged between the wetting and drying paths; however, the wetting or drying state has a pronounced influence on the water-entry pressure, the water-filled porosity at zero suction, and the saturated hydraulic conductivity. The suction stress values obtained from the shear-strength tests under both natural moisture and resaturated conditions were mostly bounded by the suction stress characteristic curves (SSCCs) obtained from the hydrologic tests. This finding experimentally confirms that the soil-water retention curve, hydraulic conductivity function, and SSCC are intrinsically related. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000786

Stability of steep slopes in cemented sands / Brian D. Collins in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 1 (Janvier 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 1 (Janvier 2011) . - pp. 27-42 Titre : Stability of steep slopes in cemented sands Type de document : texte imprimé Auteurs : Brian D. Collins, Auteur ; Sitar, Nicholas, Auteur Année de publication : 2011 Article en page(s) : pp. 27-42 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Slope  stability  Cemented  sand  Limiting  equilibrium  Tensile  strength  Lidar  Cliffs  Failure  mode Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The analysis of steep slope and cliff stability in variably cemented sands poses a significant practical challenge as routine analyses tend to underestimate the actually observed stability of existing slopes. The presented research evaluates how the degree of cementation controls the evolution of steep sand slopes and shows that the detailed slope geometry is important in determining the characteristics of the failure mode, which in turn, guide the selection of an appropriate stability analysis method. Detailed slope-profile cross sections derived from terrestrial lidar surveying of otherwise inaccessible cemented sand cliffs are used to investigate failure modes in weakly cemented [unconfined compressive strength (UCS)<30 kPa] and moderately cemented (30 DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i1/p43_s1?isAuthorized=no [article] Stability of steep slopes in cemented sands [texte imprimé] / Brian D. Collins, Auteur ; Sitar, Nicholas, Auteur . - 2011 . - pp. 27-42. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 1 (Janvier 2011) . - pp. 27-42 Mots-clés : Slope  stability  Cemented  sand  Limiting  equilibrium  Tensile  strength  Lidar  Cliffs  Failure  mode Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The analysis of steep slope and cliff stability in variably cemented sands poses a significant practical challenge as routine analyses tend to underestimate the actually observed stability of existing slopes. The presented research evaluates how the degree of cementation controls the evolution of steep sand slopes and shows that the detailed slope geometry is important in determining the characteristics of the failure mode, which in turn, guide the selection of an appropriate stability analysis method. Detailed slope-profile cross sections derived from terrestrial lidar surveying of otherwise inaccessible cemented sand cliffs are used to investigate failure modes in weakly cemented [unconfined compressive strength (UCS)<30 kPa] and moderately cemented (30 DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i1/p43_s1?isAuthorized=no

Stability of steep slopes in cemented sands / Brian D. Collins in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 1 (Janvier 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 1 (Janvier 2011) . - pp. 43-51 Titre : Stability of steep slopes in cemented sands Type de document : texte imprimé Auteurs : Brian D. Collins, Auteur ; Sitar, Nicholas, Auteur Année de publication : 2011 Article en page(s) : pp. 43-51 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Slope  stability  Cemented  sand  Limiting  equilibrium  Tensile  strength  Lidar  Cliffs  Failure  mode Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The analysis of steep slope and cliff stability in variably cemented sands poses a significant practical challenge as routine analyses tend to underestimate the actually observed stability of existing slopes. The presented research evaluates how the degree of cementation controls the evolution of steep sand slopes and shows that the detailed slope geometry is important in determining the characteristics of the failure mode, which in turn, guide the selection of an appropriate stability analysis method. Detailed slope-profile cross sections derived from terrestrial lidar surveying of otherwise inaccessible cemented sand cliffs are used to investigate failure modes in weakly cemented [unconfined compressive strength (UCS)<30 kPa] and moderately cemented (30 DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i1/p43_s1?isAuthorized=no [article] Stability of steep slopes in cemented sands [texte imprimé] / Brian D. Collins, Auteur ; Sitar, Nicholas, Auteur . - 2011 . - pp. 43-51. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 1 (Janvier 2011) . - pp. 43-51 Mots-clés : Slope  stability  Cemented  sand  Limiting  equilibrium  Tensile  strength  Lidar  Cliffs  Failure  mode Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The analysis of steep slope and cliff stability in variably cemented sands poses a significant practical challenge as routine analyses tend to underestimate the actually observed stability of existing slopes. The presented research evaluates how the degree of cementation controls the evolution of steep sand slopes and shows that the detailed slope geometry is important in determining the characteristics of the failure mode, which in turn, guide the selection of an appropriate stability analysis method. Detailed slope-profile cross sections derived from terrestrial lidar surveying of otherwise inaccessible cemented sand cliffs are used to investigate failure modes in weakly cemented [unconfined compressive strength (UCS)<30 kPa] and moderately cemented (30 DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i1/p43_s1?isAuthorized=no