Documents disponibles écrits par cet auteur

Analysis of footing load tests on aggregate pier reinforced clay / Armin W. Stuedlein in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 9 (Septembre 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 9 (Septembre 2012) . - pp.1091–1103. Titre : Analysis of footing load tests on aggregate pier reinforced clay Type de document : texte imprimé Auteurs : Armin W. Stuedlein, Auteur ; Robert D. Holtz, Auteur Année de publication : 2012 Article en page(s) : pp.1091–1103. Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Soil  stabilization  Ground  improvement  Instrumentation  Load  tests  Footings  Statistics Résumé : Despite the increased use of aggregate piers for soil reinforcement, the role of typical construction variables on footing performance remains uncertain. This paper describes a series of full-scale footing load tests conducted to evaluate the effect of aggregate gradation, pier length, and compaction method. Tests were conducted on small (0.76 m) and large (2.74 m) instrumented spread footings supported on single aggregate piers and groups of aggregate piers, respectively. The bearing pressure-displacement response of these tests is presented and the statistical significance of the construction variables is quantified for single piers using a 23 factorial analysis within an ANOVA framework. The statistical significance of the effect of pier length, gradation, and compaction was determined by controlling for the spatial variability in matrix soil strength and stiffness across the test site, which indicated that these variables were largely insignificant at the treatment levels evaluated. Additionally, no appreciable difference in the bearing pressure-displacement performance of the footings on groups of piers constructed with various levels of treatment was observed. Small variations in the observed displacement performance are attributed to sources of variability other than construction variables. The similarity in the performance of the uniformly constructed pier groups, representing production conditions, suggests that variations in the inherently variable matrix soil stiffness and strength control the aggregate pier performance. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000677 [article] Analysis of footing load tests on aggregate pier reinforced clay [texte imprimé] / Armin W. Stuedlein, Auteur ; Robert D. Holtz, Auteur . - 2012 . - pp.1091–1103. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 9 (Septembre 2012) . - pp.1091–1103. Mots-clés : Soil  stabilization  Ground  improvement  Instrumentation  Load  tests  Footings  Statistics Résumé : Despite the increased use of aggregate piers for soil reinforcement, the role of typical construction variables on footing performance remains uncertain. This paper describes a series of full-scale footing load tests conducted to evaluate the effect of aggregate gradation, pier length, and compaction method. Tests were conducted on small (0.76 m) and large (2.74 m) instrumented spread footings supported on single aggregate piers and groups of aggregate piers, respectively. The bearing pressure-displacement response of these tests is presented and the statistical significance of the construction variables is quantified for single piers using a 23 factorial analysis within an ANOVA framework. The statistical significance of the effect of pier length, gradation, and compaction was determined by controlling for the spatial variability in matrix soil strength and stiffness across the test site, which indicated that these variables were largely insignificant at the treatment levels evaluated. Additionally, no appreciable difference in the bearing pressure-displacement performance of the footings on groups of piers constructed with various levels of treatment was observed. Small variations in the observed displacement performance are attributed to sources of variability other than construction variables. The similarity in the performance of the uniformly constructed pier groups, representing production conditions, suggests that variations in the inherently variable matrix soil stiffness and strength control the aggregate pier performance. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000677

Assessment of reinforcement strains in very tall mechanically stabilized earth walls / Armin W. Stuedlein in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 3 (Mars 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 3 (Mars 2012) . - pp. 345-356 Titre : Assessment of reinforcement strains in very tall mechanically stabilized earth walls Type de document : texte imprimé Auteurs : Armin W. Stuedlein, Auteur ; Tony M. Allen, Auteur ; Robert D. Holtz, Auteur Année de publication : 2012 Article en page(s) : pp. 345-356 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Soil  stabilization  Retaining  walls  Performance  Instrumentation  Design  procedures Résumé : The grade raising associated with the Third Runway Project at Seattle-Tacoma International Airport included construction of tall mechanically stabilized earth (MSE) walls, including the near-vertical, two-tier, 26-m North MSE wall and the near-vertical, four-tier, 46-m tall west MSE wall. Twenty reinforcement strips at critical wall cross sections were instrumented with over 500 strain gauges to monitor strains during and following construction. The reinforcement loads inferred from observed strains are of interest because of their great height and global reinforcement stiffness, which place these walls outside the range in height and stiffness used to calibrate commonly used design methods. This paper presents the development and distribution of reinforcement strains measured during and following the construction of these walls. The reinforcement stresses calculated using the original reinforcement load design methods and design friction angle agreed with those inferred from the measured strains. The accuracy of two standard-of-practice and two alternate design methods is evaluated by comparing the reinforcement loads inferred from measured strains to those calculated using the actual friction angle of the reinforced fill material. Advantages and limitations in these design methods are identified, and recommendations for the improvement of some of these methods are provided. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i3/p345_s1?isAuthorized=no [article] Assessment of reinforcement strains in very tall mechanically stabilized earth walls [texte imprimé] / Armin W. Stuedlein, Auteur ; Tony M. Allen, Auteur ; Robert D. Holtz, Auteur . - 2012 . - pp. 345-356. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 3 (Mars 2012) . - pp. 345-356 Mots-clés : Soil  stabilization  Retaining  walls  Performance  Instrumentation  Design  procedures Résumé : The grade raising associated with the Third Runway Project at Seattle-Tacoma International Airport included construction of tall mechanically stabilized earth (MSE) walls, including the near-vertical, two-tier, 26-m North MSE wall and the near-vertical, four-tier, 46-m tall west MSE wall. Twenty reinforcement strips at critical wall cross sections were instrumented with over 500 strain gauges to monitor strains during and following construction. The reinforcement loads inferred from observed strains are of interest because of their great height and global reinforcement stiffness, which place these walls outside the range in height and stiffness used to calibrate commonly used design methods. This paper presents the development and distribution of reinforcement strains measured during and following the construction of these walls. The reinforcement stresses calculated using the original reinforcement load design methods and design friction angle agreed with those inferred from the measured strains. The accuracy of two standard-of-practice and two alternate design methods is evaluated by comparing the reinforcement loads inferred from measured strains to those calculated using the actual friction angle of the reinforced fill material. Advantages and limitations in these design methods are identified, and recommendations for the improvement of some of these methods are provided. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i3/p345_s1?isAuthorized=no

Bearing capacity of spread footings on aggregate pier reinforced clay / Armin W. Stuedlein 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. 49–58 Titre : Bearing capacity of spread footings on aggregate pier reinforced clay Type de document : texte imprimé Auteurs : Armin W. Stuedlein, Auteur ; Robert D. Holtz, Auteur Année de publication : 2013 Article en page(s) : pp. 49–58 Note générale : geotechnique Langues : Anglais (eng) Mots-clés : soil  stabilization;  load  tests;  footings;  load  bearing  capacity;  clays;  spread  foundations Résumé : Aggregate piers, also known as stone columns, are a commonly used ground improvement technique to stiffen existing soils for the support of structure foundations. This paper presents an evaluation of existing analytical expressions for the bearing capacity of spread footings supported on aggregate pier reinforced clay. The accuracy of these models was investigated using a database of high-quality footing load test data. The existing models were compared using the bias (i.e., the ratio of measured and calculated bearing capacity), and they produced a wide range in predicted bearing capacities. Selected analytical models were empirically modified using the load test database, and this resulted in improved accuracy and reduced variability. Back-calculated aggregate pier bearing capacity and cavity expansion factors are shown to be inversely proportional to undrained shear strength, and therefore to the ultimate confining pressure available at failure. This finding is attributed to the curved failure envelope of the angular aggregate used in pier construction. Additionally, a multiple nonlinear regression model suitable for spread footings resting on aggregate piers under a wide range of pier configurations is presented. The regression model is shown to produce more accurate bearing capacity estimates than existing analytical models. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000748 [article] Bearing capacity of spread footings on aggregate pier reinforced clay [texte imprimé] / Armin W. Stuedlein, Auteur ; Robert D. Holtz, Auteur . - 2013 . - pp. 49–58. geotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 1 (Janvier 2013) . - pp. 49–58 Mots-clés : soil  stabilization;  load  tests;  footings;  load  bearing  capacity;  clays;  spread  foundations Résumé : Aggregate piers, also known as stone columns, are a commonly used ground improvement technique to stiffen existing soils for the support of structure foundations. This paper presents an evaluation of existing analytical expressions for the bearing capacity of spread footings supported on aggregate pier reinforced clay. The accuracy of these models was investigated using a database of high-quality footing load test data. The existing models were compared using the bias (i.e., the ratio of measured and calculated bearing capacity), and they produced a wide range in predicted bearing capacities. Selected analytical models were empirically modified using the load test database, and this resulted in improved accuracy and reduced variability. Back-calculated aggregate pier bearing capacity and cavity expansion factors are shown to be inversely proportional to undrained shear strength, and therefore to the ultimate confining pressure available at failure. This finding is attributed to the curved failure envelope of the angular aggregate used in pier construction. Additionally, a multiple nonlinear regression model suitable for spread footings resting on aggregate piers under a wide range of pier configurations is presented. The regression model is shown to produce more accurate bearing capacity estimates than existing analytical models. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000748