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Ajouter le résultat dans votre panierOn global equilibrium in design of geosynthetic reinforced walls / Leshchinsky, Dov in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N°3 (Mars 2009)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 309–315
Titre : On global equilibrium in design of geosynthetic reinforced walls Type de document : texte imprimé Auteurs : Leshchinsky, Dov, Auteur Année de publication : 2009 Article en page(s) : pp. 309–315 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Equilibrium Walls Geosynthetics Earth pressure Design Soil stabilization Résumé : Common design of MSE walls is based on a lateral earth pressure approach. A key aspect in design is the determination of the reactive force in each reinforcement layer so as to maintain the system in equilibrium. This force leads to the selection of reinforcement with adequate long term strength. It is also used to calculate the pullout resistive length needed to ensure the capacity of each layer to develop strength. Lateral earth pressures used in design may or may not satisfy basic global equilibrium of the reinforced soil mass. Hence, the present work establishes a benchmark test using a simple statically determinate approach, in order to check if different design procedures satisfy equilibrium. Basic statics indicate that such a test is necessary, but not sufficient, to ascertain the validity of the calculated reactive force. Three existing design methods are examined: AASHTO, National Concrete Masonry Association, and Ko -stiffness. AASHTO, which is the simplest to apply and generally considered conservative, satisfies the benchmark test. However, it may yield very conservative results if one considers the facing to play a major role. NCMA is likely satisfactory if one explicitly accounts for the facing shear resistance in assessing the reaction in the reinforcement. The emerging Ko -stiffness approach, which is empirical, may violate statics potentially leading to underestimation of the reinforcement force. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2830 [...] [article] On global equilibrium in design of geosynthetic reinforced walls [texte imprimé] / Leshchinsky, Dov, Auteur . - 2009 . - pp. 309–315.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 309–315
Mots-clés : Equilibrium Walls Geosynthetics Earth pressure Design Soil stabilization Résumé : Common design of MSE walls is based on a lateral earth pressure approach. A key aspect in design is the determination of the reactive force in each reinforcement layer so as to maintain the system in equilibrium. This force leads to the selection of reinforcement with adequate long term strength. It is also used to calculate the pullout resistive length needed to ensure the capacity of each layer to develop strength. Lateral earth pressures used in design may or may not satisfy basic global equilibrium of the reinforced soil mass. Hence, the present work establishes a benchmark test using a simple statically determinate approach, in order to check if different design procedures satisfy equilibrium. Basic statics indicate that such a test is necessary, but not sufficient, to ascertain the validity of the calculated reactive force. Three existing design methods are examined: AASHTO, National Concrete Masonry Association, and Ko -stiffness. AASHTO, which is the simplest to apply and generally considered conservative, satisfies the benchmark test. However, it may yield very conservative results if one considers the facing to play a major role. NCMA is likely satisfactory if one explicitly accounts for the facing shear resistance in assessing the reaction in the reinforcement. The emerging Ko -stiffness approach, which is empirical, may violate statics potentially leading to underestimation of the reinforcement force. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2830 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 316–332
Titre : Case study of a full-scale evapotranspiration cover Type de document : texte imprimé Auteurs : Patrick E. McGuire, Auteur ; Brian J. Andraski, Auteur ; Ryan E. Archibald, Auteur Année de publication : 2009 Article en page(s) : pp. 316–332 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Landfills Design Performance characteristics Soil properties Monitoring Evapotranspiration Résumé : The design, construction, and performance analyses of a 6.1ha evapotranspiration (ET) landfill cover at the semiarid U.S. Army Fort Carson site, near Colorado Springs, Colo. are presented. Initial water-balance model simulations, using literature reported soil hydraulic data, aided selection of borrow-source soil type(s) that resulted in predictions of negligible annual drainage (⩽1mm∕year) . Final construction design was based on refined water-balance simulations using laboratory determined soil hydraulic values from borrow area natural soil horizons that were described with USDA soil classification methods. Cover design components included a 122cm thick clay loam (USDA), compaction ⩽80% of the standard Proctor maximum dry density (dry bulk density ∼1.3Mg/m3 ), erosion control measures, top soil amended with biosolids, and seeding with native grasses. Favorable hydrologic performance for a 5year period was documented by lysimeter-measured and Richards’-based calculations of annual drainage that were all <0.4mm∕year . Water potential data suggest that ET removed water that infiltrated the cover and contributed to a persistent driving force for upward flow and removal of water from below the base of the cover. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2831 [...] [article] Case study of a full-scale evapotranspiration cover [texte imprimé] / Patrick E. McGuire, Auteur ; Brian J. Andraski, Auteur ; Ryan E. Archibald, Auteur . - 2009 . - pp. 316–332.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 316–332
Mots-clés : Landfills Design Performance characteristics Soil properties Monitoring Evapotranspiration Résumé : The design, construction, and performance analyses of a 6.1ha evapotranspiration (ET) landfill cover at the semiarid U.S. Army Fort Carson site, near Colorado Springs, Colo. are presented. Initial water-balance model simulations, using literature reported soil hydraulic data, aided selection of borrow-source soil type(s) that resulted in predictions of negligible annual drainage (⩽1mm∕year) . Final construction design was based on refined water-balance simulations using laboratory determined soil hydraulic values from borrow area natural soil horizons that were described with USDA soil classification methods. Cover design components included a 122cm thick clay loam (USDA), compaction ⩽80% of the standard Proctor maximum dry density (dry bulk density ∼1.3Mg/m3 ), erosion control measures, top soil amended with biosolids, and seeding with native grasses. Favorable hydrologic performance for a 5year period was documented by lysimeter-measured and Richards’-based calculations of annual drainage that were all <0.4mm∕year . Water potential data suggest that ET removed water that infiltrated the cover and contributed to a persistent driving force for upward flow and removal of water from below the base of the cover. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2831 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 333–348
Titre : Field data and water-balance predictions for a monolithic cover in a semiarid climate Type de document : texte imprimé Auteurs : G. L. Bohnhoff, Auteur ; A. S. Ogorzalek, Auteur ; C. H. Benson, Auteur Année de publication : 2009 Article en page(s) : pp. 333–348 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Evapotranspiration Landfill Numerical model Unsaturated flow Waste management Water balance Unsaturated soils Arid lands Field tests Résumé : Water-balance predictions made using four codes (UNSAT-H, VADOSE/W, HYDRUS, and LEACHM) are compared with water-balance data from a test section located in a semiarid climate simulating a monolithic water-balance cover. The accuracy of the runoff prediction (underprediction or overprediction) was found to affect the accuracy of all other water-balance quantities. Runoff was predicted more accurately when precipitation was applied uniformly throughout the day, the surface layer was assigned higher saturated hydraulic conductivity, or when Brooks-Corey functions were used to describe the hydraulic properties of the cover soils. However, no definitive or universal recommendation could be identified that would provide reasonable assurance that runoff mechanisms are properly simulated and runoff predictions are accurate. Evapotranspiration and soil-water storage were predicted reasonably well (within ≈25mm∕yr ) when runoff was predicted accurately, general mean hydraulic properties were used as input, and the vegetation followed a consistent seasonal transpiration cycle. However, percolation was consistently underpredicted ( >3mm total) even when evapotranspiration and soil-water storage were predicted reliably. Better agreement between measured and predicted percolation (or a more conservative prediction) was obtained using mean properties for the soil-water characteristic curve and increasing the saturated hydraulic conductivity of the cover soils by a factor between 5 and 10. Evapotranspiration and soil-water storage were predicted poorly at the end of the monitoring period by all of the codes due to a change in the evapotranspiration pattern that was not captured by the models. The inability to capture such changes is a weakness in current modeling approaches that needs further study. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2833 [...] [article] Field data and water-balance predictions for a monolithic cover in a semiarid climate [texte imprimé] / G. L. Bohnhoff, Auteur ; A. S. Ogorzalek, Auteur ; C. H. Benson, Auteur . - 2009 . - pp. 333–348.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 333–348
Mots-clés : Evapotranspiration Landfill Numerical model Unsaturated flow Waste management Water balance Unsaturated soils Arid lands Field tests Résumé : Water-balance predictions made using four codes (UNSAT-H, VADOSE/W, HYDRUS, and LEACHM) are compared with water-balance data from a test section located in a semiarid climate simulating a monolithic water-balance cover. The accuracy of the runoff prediction (underprediction or overprediction) was found to affect the accuracy of all other water-balance quantities. Runoff was predicted more accurately when precipitation was applied uniformly throughout the day, the surface layer was assigned higher saturated hydraulic conductivity, or when Brooks-Corey functions were used to describe the hydraulic properties of the cover soils. However, no definitive or universal recommendation could be identified that would provide reasonable assurance that runoff mechanisms are properly simulated and runoff predictions are accurate. Evapotranspiration and soil-water storage were predicted reasonably well (within ≈25mm∕yr ) when runoff was predicted accurately, general mean hydraulic properties were used as input, and the vegetation followed a consistent seasonal transpiration cycle. However, percolation was consistently underpredicted ( >3mm total) even when evapotranspiration and soil-water storage were predicted reliably. Better agreement between measured and predicted percolation (or a more conservative prediction) was obtained using mean properties for the soil-water characteristic curve and increasing the saturated hydraulic conductivity of the cover soils by a factor between 5 and 10. Evapotranspiration and soil-water storage were predicted poorly at the end of the monitoring period by all of the codes due to a change in the evapotranspiration pattern that was not captured by the models. The inability to capture such changes is a weakness in current modeling approaches that needs further study. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2833 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 349–358
Titre : Relative abundance of monovalent and divalent cations and the impact of desiccation on geosynthetic clay liners Type de document : texte imprimé Auteurs : Craig H. Benson, Auteur ; Stephen R. Meer, Auteur Année de publication : 2009 Article en page(s) : pp. 349–358 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Clay liners Landfill Geosynthetics Hydraulic conductivity Résumé : Laboratory experiments were conducted on a geosynthetic clay liner (GCL) containing Na–bentonite to determine how the swell index and hydraulic conductivity of GCLs are affected by wet-dry cycling with solutions having different relative abundance of monovalent and multivalent cations. Relative abundance of monovalent and multivalent cations was characterized by the RMD of the test solution, which is defined as the ratio of the total molarity of monovalent cations to the square root of the total molarity of multivalent cations at a given ionic strength. RMD was found to control the final swell index, relative abundance of monovalent and divalent cations in the final exchange complex, and the final hydraulic conductivity of bentonite exposed to wet-dry cycling. Ionic strength affects the number of wet-dry cycles required for a change in hydraulic conductivity to occur and the rate of change in swell index. Large increases in hydraulic conductivity and loss of swelling capacity occurred for solutions having RMD⩽0.07M1∕2 . Modest or small changes in hydraulic conductivity and swell index were obtained when the RMD was ⩾0.14M1∕2 . These findings suggest that chemical analysis of the pore water in cover soils may prove useful in evaluating the compatibility of GCLs and cover soils used in applications where wet-dry cycling may occur. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2834 [...] [article] Relative abundance of monovalent and divalent cations and the impact of desiccation on geosynthetic clay liners [texte imprimé] / Craig H. Benson, Auteur ; Stephen R. Meer, Auteur . - 2009 . - pp. 349–358.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 349–358
Mots-clés : Clay liners Landfill Geosynthetics Hydraulic conductivity Résumé : Laboratory experiments were conducted on a geosynthetic clay liner (GCL) containing Na–bentonite to determine how the swell index and hydraulic conductivity of GCLs are affected by wet-dry cycling with solutions having different relative abundance of monovalent and multivalent cations. Relative abundance of monovalent and multivalent cations was characterized by the RMD of the test solution, which is defined as the ratio of the total molarity of monovalent cations to the square root of the total molarity of multivalent cations at a given ionic strength. RMD was found to control the final swell index, relative abundance of monovalent and divalent cations in the final exchange complex, and the final hydraulic conductivity of bentonite exposed to wet-dry cycling. Ionic strength affects the number of wet-dry cycles required for a change in hydraulic conductivity to occur and the rate of change in swell index. Large increases in hydraulic conductivity and loss of swelling capacity occurred for solutions having RMD⩽0.07M1∕2 . Modest or small changes in hydraulic conductivity and swell index were obtained when the RMD was ⩾0.14M1∕2 . These findings suggest that chemical analysis of the pore water in cover soils may prove useful in evaluating the compatibility of GCLs and cover soils used in applications where wet-dry cycling may occur. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2834 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 359–370
Titre : Normal fault rupture interaction with strip foundations Type de document : texte imprimé Auteurs : I. Anastasopoulos, Auteur ; G. Gazetas, Auteur ; M. F. Bransby, Auteur Année de publication : 2009 Article en page(s) : pp. 359–370 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Geological faults Soil-structure interaction Finite element method Centrifuge models Seismic effects Foundations Résumé : Observations after earthquakes where surface fault ruptures crossed engineering facilities reveal that some structures survived the rupture almost unscathed. In some cases, the rupture path appears to divert, “avoiding” the structure. Such observations point to an interaction between the propagating rupture, the soil, and the foundation. This paper (i) develops a two-step nonlinear finite-element methodology to study rupture propagation and its interaction with strip foundations; (ii) provides validation through successful Class “A” predictions of centrifuge model tests; and (iii) conducts a parameter study on the interaction of strip foundations with normal fault ruptures. It is shown that a heavily loaded foundation can substantially divert the rupture path, which may avoid outcropping underneath the foundation. The latter undergoes rigid body rotation, often detaching from the soil. Its distress arises mainly from the ensuing loss of support that takes place either at the edges or around its center. The average pressure q on the foundation largely dictates the width of such unsupported spans. Increasing q decreases the unsupported width, reducing foundation distress. The role of q is dual: (1) it compresses the soil, “flattening” fault-induced surface “anomalies”; and (2) it changes the stress field underneath the foundation, facilitating rupture diversion. However, even if the rupture is diverted, the foundation may undergo significant stressing, depending on its position relative to the fault outcrop. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2835 [...] [article] Normal fault rupture interaction with strip foundations [texte imprimé] / I. Anastasopoulos, Auteur ; G. Gazetas, Auteur ; M. F. Bransby, Auteur . - 2009 . - pp. 359–370.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 359–370
Mots-clés : Geological faults Soil-structure interaction Finite element method Centrifuge models Seismic effects Foundations Résumé : Observations after earthquakes where surface fault ruptures crossed engineering facilities reveal that some structures survived the rupture almost unscathed. In some cases, the rupture path appears to divert, “avoiding” the structure. Such observations point to an interaction between the propagating rupture, the soil, and the foundation. This paper (i) develops a two-step nonlinear finite-element methodology to study rupture propagation and its interaction with strip foundations; (ii) provides validation through successful Class “A” predictions of centrifuge model tests; and (iii) conducts a parameter study on the interaction of strip foundations with normal fault ruptures. It is shown that a heavily loaded foundation can substantially divert the rupture path, which may avoid outcropping underneath the foundation. The latter undergoes rigid body rotation, often detaching from the soil. Its distress arises mainly from the ensuing loss of support that takes place either at the edges or around its center. The average pressure q on the foundation largely dictates the width of such unsupported spans. Increasing q decreases the unsupported width, reducing foundation distress. The role of q is dual: (1) it compresses the soil, “flattening” fault-induced surface “anomalies”; and (2) it changes the stress field underneath the foundation, facilitating rupture diversion. However, even if the rupture is diverted, the foundation may undergo significant stressing, depending on its position relative to the fault outcrop. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2835 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 371–386
Titre : Probabilistic models for cyclic straining of saturated clean sands Type de document : texte imprimé Auteurs : K. Onder Cetin, Auteur ; H. Tolga Bilge, Auteur ; Jiaer Wu, Auteur Année de publication : 2009 Article en page(s) : pp. 371–386 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Cyclic tests Shear strain Volume change Probability Sand Résumé : A maximum likelihood framework for the probabilistic assessment of postcyclic straining of saturated clean sands is described. Databases consisting of cyclic laboratory test results including maximum shear and postcyclic volumetric strains in conjunction with relative density, number of stress (strain) cycles, and “index” test results were used for the development of probabilistically based postcyclic strain correlations. For this purpose, in addition to the compilation of existing data from literature, a series of stress-controlled cyclic triaxial and simple shear tests were performed on laboratory-constituted saturated clean sand specimens. The variabilities in testing conditions (i.e., type of test, consolidation procedure, confining pressure, rate of loading, etc.) were corrected through a series of correction schemes, the effectiveness of which were later confirmed by the discriminant analyses results. Volumetric and shear strain boundary curves were developed in the cyclic stress ratio versus N1,60,CS or qc,1 domain. In addition to being based on significantly extended and higher quality databases, contrary to the existing judgmentally derived deterministic ones, proposed correlations have formal probabilistic bases, and so provide insight regarding uncertainty of strain predictions or probability of exceeding a target strain value. Probabilistic uses of the proposed correlations were illustrated by three sets of examples. A companion paper applied and calibrated the proposed volumetric strain correlation to semiempirically evaluate postearthquake settlement of level, free-field sites. For the calibration, case history soil profiles, composed of a broad range of sand types and depositional characteristics, shaken by a number of earthquakes, were used. Superior predictions of field settlements by this laboratory data-based cyclic strain assessment approach were concluded to be strongly mutually supportive. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2837 [...] [article] Probabilistic models for cyclic straining of saturated clean sands [texte imprimé] / K. Onder Cetin, Auteur ; H. Tolga Bilge, Auteur ; Jiaer Wu, Auteur . - 2009 . - pp. 371–386.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 371–386
Mots-clés : Cyclic tests Shear strain Volume change Probability Sand Résumé : A maximum likelihood framework for the probabilistic assessment of postcyclic straining of saturated clean sands is described. Databases consisting of cyclic laboratory test results including maximum shear and postcyclic volumetric strains in conjunction with relative density, number of stress (strain) cycles, and “index” test results were used for the development of probabilistically based postcyclic strain correlations. For this purpose, in addition to the compilation of existing data from literature, a series of stress-controlled cyclic triaxial and simple shear tests were performed on laboratory-constituted saturated clean sand specimens. The variabilities in testing conditions (i.e., type of test, consolidation procedure, confining pressure, rate of loading, etc.) were corrected through a series of correction schemes, the effectiveness of which were later confirmed by the discriminant analyses results. Volumetric and shear strain boundary curves were developed in the cyclic stress ratio versus N1,60,CS or qc,1 domain. In addition to being based on significantly extended and higher quality databases, contrary to the existing judgmentally derived deterministic ones, proposed correlations have formal probabilistic bases, and so provide insight regarding uncertainty of strain predictions or probability of exceeding a target strain value. Probabilistic uses of the proposed correlations were illustrated by three sets of examples. A companion paper applied and calibrated the proposed volumetric strain correlation to semiempirically evaluate postearthquake settlement of level, free-field sites. For the calibration, case history soil profiles, composed of a broad range of sand types and depositional characteristics, shaken by a number of earthquakes, were used. Superior predictions of field settlements by this laboratory data-based cyclic strain assessment approach were concluded to be strongly mutually supportive. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2837 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 387–398
Titre : Probabilistic model for the assessment of cyclically induced reconsolidation (volumetric) settlements Type de document : texte imprimé Auteurs : K. Onder Cetin, Auteur ; H. Tolga Bilge, Auteur ; Jiaer Wu, Auteur Année de publication : 2009 Article en page(s) : pp. 387–398 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Volume change Settlement Probability Soil liquefaction Soil consolidation Résumé : A maximum likelihood framework for the probabilistic assessment of cyclically induced reconsolidation settlements of saturated cohesionless soil sites is described. For this purpose, over 200 case history sites were carefully studied. After screening for data quality and completeness, the resulting database is composed of 49 high-quality, cyclically induced ground settlement case histories from seven different earthquakes. For these case history sites, settlement predictions by currently available methods of Tokimatsu and Seed (1984), Ishihara and Yoshimine (1992), Shamoto et al. (1998), and Wu and Seed (2004) are presented comparatively, along with the predictions of the proposed probabilistic model. As an integral part of the proposed model, the volumetric strain correlation presented in the companion paper is used. The accuracy of the mean predictions as well as their uncertainty is assessed by both linear regression and maximum likelihood methodologies. The analyses results revealed that (1) the predictions of Shamoto et al. and Tokimatsu and Seed are smaller than the actual settlements and need to be calibrated by a factor of 1.93 and 1.45, respectively; and (2) Ishihara and Yoshimine, and Wu and Seed predictions are higher than the actual settlements and need to be calibrated by a factor of 0.90 and 0.98, respectively. The Wu and Seed procedure produced the most unbiased estimates of mean settlements [i.e., their calibration coefficient (0.98) is the closest to unity], but the uncertainty (scatter) of their predictions remains high as revealed by the second to last smaller R2 value, or relatively higher standard deviation (σε) of the model error. In addition to superior model predictions, the main advantage of the proposed methodology is the probabilistic nature of the calibration scheme, which enables incorporation of the model uncertainty into mean settlement predictions. To illustrate the potential use of the proposed model, the probability of cyclically induced reconsolidation settlement of a site after a scenario earthquake to be less than a threshold settlement level is assessed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2838 [...] [article] Probabilistic model for the assessment of cyclically induced reconsolidation (volumetric) settlements [texte imprimé] / K. Onder Cetin, Auteur ; H. Tolga Bilge, Auteur ; Jiaer Wu, Auteur . - 2009 . - pp. 387–398.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 387–398
Mots-clés : Volume change Settlement Probability Soil liquefaction Soil consolidation Résumé : A maximum likelihood framework for the probabilistic assessment of cyclically induced reconsolidation settlements of saturated cohesionless soil sites is described. For this purpose, over 200 case history sites were carefully studied. After screening for data quality and completeness, the resulting database is composed of 49 high-quality, cyclically induced ground settlement case histories from seven different earthquakes. For these case history sites, settlement predictions by currently available methods of Tokimatsu and Seed (1984), Ishihara and Yoshimine (1992), Shamoto et al. (1998), and Wu and Seed (2004) are presented comparatively, along with the predictions of the proposed probabilistic model. As an integral part of the proposed model, the volumetric strain correlation presented in the companion paper is used. The accuracy of the mean predictions as well as their uncertainty is assessed by both linear regression and maximum likelihood methodologies. The analyses results revealed that (1) the predictions of Shamoto et al. and Tokimatsu and Seed are smaller than the actual settlements and need to be calibrated by a factor of 1.93 and 1.45, respectively; and (2) Ishihara and Yoshimine, and Wu and Seed predictions are higher than the actual settlements and need to be calibrated by a factor of 0.90 and 0.98, respectively. The Wu and Seed procedure produced the most unbiased estimates of mean settlements [i.e., their calibration coefficient (0.98) is the closest to unity], but the uncertainty (scatter) of their predictions remains high as revealed by the second to last smaller R2 value, or relatively higher standard deviation (σε) of the model error. In addition to superior model predictions, the main advantage of the proposed methodology is the probabilistic nature of the calibration scheme, which enables incorporation of the model uncertainty into mean settlement predictions. To illustrate the potential use of the proposed model, the probability of cyclically induced reconsolidation settlement of a site after a scenario earthquake to be less than a threshold settlement level is assessed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2838 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 399–406
Titre : Near-field effects on array-based surface wave methods with active sources Type de document : texte imprimé Auteurs : Sungsoo Yoon, Auteur ; Glenn J. Rix, Auteur Année de publication : 2009 Article en page(s) : pp. 399–406 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Surface waves Rayleigh waves Simulation Parameters Résumé : Although the capabilities of engineering surface wave methods have improved in recent years due to several advances, a number of issues still require study to further improve the capabilities of modern surface wave methods. Near-field effects, which are one of these issues, have been studied for traditional surface wave methods with two receivers, and several criteria to mitigate the effects have been recommended. However, these criteria are not applicable to surface wave methods with multiple receivers. Moreover, the criteria are not quantitatively based and do not account for different types of soil profiles, which strongly influence near-field effects. A new study of near-field effects on surface wave methods with multiple receivers was conducted via numerical simulations, laboratory simulations, and field tests. Quantitatively based criteria for near-field effects in different soil profiles are presented using two normalized parameters developed in this study. There was excellent agreement between numerical and experimental results, and it was found that underestimation of measured Rayleigh phase velocities was the major symptom of near-field effects. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2839 [...] [article] Near-field effects on array-based surface wave methods with active sources [texte imprimé] / Sungsoo Yoon, Auteur ; Glenn J. Rix, Auteur . - 2009 . - pp. 399–406.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 399–406
Mots-clés : Surface waves Rayleigh waves Simulation Parameters Résumé : Although the capabilities of engineering surface wave methods have improved in recent years due to several advances, a number of issues still require study to further improve the capabilities of modern surface wave methods. Near-field effects, which are one of these issues, have been studied for traditional surface wave methods with two receivers, and several criteria to mitigate the effects have been recommended. However, these criteria are not applicable to surface wave methods with multiple receivers. Moreover, the criteria are not quantitatively based and do not account for different types of soil profiles, which strongly influence near-field effects. A new study of near-field effects on surface wave methods with multiple receivers was conducted via numerical simulations, laboratory simulations, and field tests. Quantitatively based criteria for near-field effects in different soil profiles are presented using two normalized parameters developed in this study. There was excellent agreement between numerical and experimental results, and it was found that underestimation of measured Rayleigh phase velocities was the major symptom of near-field effects. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2839 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 407–419
Titre : Contact interface model for shallow foundations subjected to combined cyclic loading Type de document : texte imprimé Auteurs : Sivapalan Gajan, Auteur ; Kutter, Bruce L., Auteur Année de publication : 2009 Article en page(s) : pp. 407–419 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Shallow foundations Ductility Cyclic loads Combined loads Contact pressure Résumé : It has been recognized that the ductility demands on a superstructure might be reduced by allowing rocking behavior and mobilization of the ultimate capacity of shallow foundations during seismic loading. However, the absence of practical reliable foundation modeling techniques to accurately design foundations with the desired capacity and energy dissipation characteristics and concerns about permanent deformations have hindered the use of nonlinear soil–foundation–structure interaction as a designed mechanism for improving performance of structural systems. This paper presents a new “contact interface model” that has been developed to provide nonlinear relations between cyclic loads and displacements of the footing–soil system during combined cyclic loading (vertical, shear, and moment). The rigid footing and the soil beneath the footing in the zone of influence, considered as a macroelement, are modeled by keeping track of the geometry of the soil surface beneath the footing, along with the kinematics of the footing–soil system, interaction diagrams in vertical, shear, and moment space, and the introduction of a parameter, critical contact area ratio (A∕Ac) ; the ratio of footing area (A) to the footing contact area required to support vertical and shear loads (Ac) . Several contact interface model simulations were carried out and the model simulations are compared with centrifuge model test results. Using only six user-defined model input parameters, the contact interface model is capable of capturing the essential features (load capacities, stiffness degradation, energy dissipation, and deformations) of shallow foundations subjected to combined cyclic loading. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2840 [...] [article] Contact interface model for shallow foundations subjected to combined cyclic loading [texte imprimé] / Sivapalan Gajan, Auteur ; Kutter, Bruce L., Auteur . - 2009 . - pp. 407–419.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 407–419
Mots-clés : Shallow foundations Ductility Cyclic loads Combined loads Contact pressure Résumé : It has been recognized that the ductility demands on a superstructure might be reduced by allowing rocking behavior and mobilization of the ultimate capacity of shallow foundations during seismic loading. However, the absence of practical reliable foundation modeling techniques to accurately design foundations with the desired capacity and energy dissipation characteristics and concerns about permanent deformations have hindered the use of nonlinear soil–foundation–structure interaction as a designed mechanism for improving performance of structural systems. This paper presents a new “contact interface model” that has been developed to provide nonlinear relations between cyclic loads and displacements of the footing–soil system during combined cyclic loading (vertical, shear, and moment). The rigid footing and the soil beneath the footing in the zone of influence, considered as a macroelement, are modeled by keeping track of the geometry of the soil surface beneath the footing, along with the kinematics of the footing–soil system, interaction diagrams in vertical, shear, and moment space, and the introduction of a parameter, critical contact area ratio (A∕Ac) ; the ratio of footing area (A) to the footing contact area required to support vertical and shear loads (Ac) . Several contact interface model simulations were carried out and the model simulations are compared with centrifuge model test results. Using only six user-defined model input parameters, the contact interface model is capable of capturing the essential features (load capacities, stiffness degradation, energy dissipation, and deformations) of shallow foundations subjected to combined cyclic loading. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2840 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 420–430
Titre : Load-settlement response of rectangular and circular piles in multilayered soil Type de document : texte imprimé Auteurs : H. Seo, Auteur ; B. Basu, Auteur ; M. Prezzi, Auteur Année de publication : 2009 Article en page(s) : pp. 420–430 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Elastic analysis Piles Settlement Layered soils Variational principles Résumé : Traditionally, analyses developed for circular piles have also been used for rectangular piles by replacing in calculations the rectangular pile with a circular pile of equivalent area. In this paper, we present a settlement analysis that applies to piles with either rectangular or circular cross sections installed in multilayered soil deposits. The analysis follows from the solution of the differential equations governing the displacements of the pile-soil system obtained using variational principles. The input parameters needed for the analysis are the pile geometry and the elastic constants of the soil and pile. Pile displacements and vertical soil displacements calculated using this analysis match well those from finite-element analysis. A parametric study highlights some important insights for rectangular and circular piles in multilayered soil. A user-friendly spreadsheet program (ALPAXL) was developed to facilitate the use of the analysis. Examples illustrate the use of the analysis in design. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2842 [...] [article] Load-settlement response of rectangular and circular piles in multilayered soil [texte imprimé] / H. Seo, Auteur ; B. Basu, Auteur ; M. Prezzi, Auteur . - 2009 . - pp. 420–430.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 420–430
Mots-clés : Elastic analysis Piles Settlement Layered soils Variational principles Résumé : Traditionally, analyses developed for circular piles have also been used for rectangular piles by replacing in calculations the rectangular pile with a circular pile of equivalent area. In this paper, we present a settlement analysis that applies to piles with either rectangular or circular cross sections installed in multilayered soil deposits. The analysis follows from the solution of the differential equations governing the displacements of the pile-soil system obtained using variational principles. The input parameters needed for the analysis are the pile geometry and the elastic constants of the soil and pile. Pile displacements and vertical soil displacements calculated using this analysis match well those from finite-element analysis. A parametric study highlights some important insights for rectangular and circular piles in multilayered soil. A user-friendly spreadsheet program (ALPAXL) was developed to facilitate the use of the analysis. Examples illustrate the use of the analysis in design. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2842 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 431–443
Titre : Reliability analysis of laterally loaded piles involving nonlinear soil and pile behavior Type de document : texte imprimé Auteurs : C. L. Chan, Auteur ; B. K. Low, Auteur Année de publication : 2009 Article en page(s) : pp. 431–443 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Correlation Design Failure modes Limit states Monte Carlo method Nonlinear analysis Optimization Pile lateral loads Reliability Soil properties Résumé : An alternative approach of analyzing laterally loaded piles in the ubiquitous spreadsheet platform is presented. The numerical procedure couples nonlinear pile flexural rigidity (EpIp) with nonlinear p-y analysis. The deterministic study is then extended to carry out reliability analysis, which reflects the uncertainties and correlation structure of the underlying parameters. The reliability index is evaluated based on the alternative intuitive perspective of an expanding equivalent ellipsoid in the original space of the random variables. This paper investigates two modes of failure: deflection and bending moment, and considers non-normal random variables. Spatial variability of the soil medium is accounted for by incorporating an autocorrelation model. The spreadsheet-based reliability approach can also be coupled with stand-alone programs via the response surface method. The probabilities of failure inferred from reliability indices agree well with Monte Carlo simulations. Simple reliability-based design is demonstrated, in which the appropriate pile section or length that satisfies target reliability in one or more limit states is sought. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2843 [...] [article] Reliability analysis of laterally loaded piles involving nonlinear soil and pile behavior [texte imprimé] / C. L. Chan, Auteur ; B. K. Low, Auteur . - 2009 . - pp. 431–443.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 431–443
Mots-clés : Correlation Design Failure modes Limit states Monte Carlo method Nonlinear analysis Optimization Pile lateral loads Reliability Soil properties Résumé : An alternative approach of analyzing laterally loaded piles in the ubiquitous spreadsheet platform is presented. The numerical procedure couples nonlinear pile flexural rigidity (EpIp) with nonlinear p-y analysis. The deterministic study is then extended to carry out reliability analysis, which reflects the uncertainties and correlation structure of the underlying parameters. The reliability index is evaluated based on the alternative intuitive perspective of an expanding equivalent ellipsoid in the original space of the random variables. This paper investigates two modes of failure: deflection and bending moment, and considers non-normal random variables. Spatial variability of the soil medium is accounted for by incorporating an autocorrelation model. The spreadsheet-based reliability approach can also be coupled with stand-alone programs via the response surface method. The probabilities of failure inferred from reliability indices agree well with Monte Carlo simulations. Simple reliability-based design is demonstrated, in which the appropriate pile section or length that satisfies target reliability in one or more limit states is sought. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2843 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 444–448
Titre : Critical pool level and stability of slopes in granular soils Type de document : texte imprimé Auteurs : Radoslaw L. Michalowski, Auteur Année de publication : 2009 Article en page(s) : pp. 444–448 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Slopes Limit states Failures Submerging Pore water pressure Résumé : The influence of pore-water pressure and the pool water pressure on stability of submerged slopes was investigated using the kinematic approach of limit analysis. For soils with some cohesive component of strength, the critical pool level is slightly below half of the slope height, whereas for slopes built of purely granular soils the critical pool level is not well defined. The most critical mechanism of failure for submerged granular slopes was found to have the failure surface intersecting the face of the slope, with one intersection point above, and the other one below the pool level. The solution to the stability problem was found to be independent of the length scale (slope height), and equally critical mechanisms of failure can be triggered “locally” with any water level in the pool. The safety factor associated with these mechanisms is lower than the well-known factor defined by a planar failure surface approaching the slope face. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2844 [...] [article] Critical pool level and stability of slopes in granular soils [texte imprimé] / Radoslaw L. Michalowski, Auteur . - 2009 . - pp. 444–448.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 444–448
Mots-clés : Slopes Limit states Failures Submerging Pore water pressure Résumé : The influence of pore-water pressure and the pool water pressure on stability of submerged slopes was investigated using the kinematic approach of limit analysis. For soils with some cohesive component of strength, the critical pool level is slightly below half of the slope height, whereas for slopes built of purely granular soils the critical pool level is not well defined. The most critical mechanism of failure for submerged granular slopes was found to have the failure surface intersecting the face of the slope, with one intersection point above, and the other one below the pool level. The solution to the stability problem was found to be independent of the length scale (slope height), and equally critical mechanisms of failure can be triggered “locally” with any water level in the pool. The safety factor associated with these mechanisms is lower than the well-known factor defined by a planar failure surface approaching the slope face. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2844 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 449–454
Titre : Influence of particle properties and initial specimen state on one-dimensional compression and hydraulic conductivity Type de document : texte imprimé Auteurs : Jason T. DeJong, Auteur ; G. Geoffrey Christoph, Auteur Année de publication : 2009 Article en page(s) : pp. 449–454 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Crushing Hydraulic conductivity Compression Sand Particles Résumé : Particle crushing can adversely affect geotechnical system performance; examples include clogging in wells, pile shaft capacity degradation, and postconstruction settlements. The generation of fines results in volumetric compression and a reduction hydraulic conductivity, which is important for geotechnical systems whose performance is directly dependent on pore pressure dissipation, groundwater flow, or hydraulic pumping. Knowledge of hydraulic conductivity change is poorly understood due to limited experimental data, and an ability to predict this change is lacking. The role of single particle properties, initial specimen state conditions, and loading conditions on the evolution of hydraulic conductivity with particle crushing was examined experimentally. Specimen response exhibited an overshoot behavior and the convergence to a unique condition independent of initial relative density, gradation, and particle shape. The hydraulic conductivity decreased by 2–3 times before specimen yield, and by 2–3 orders of magnitude after specimen yield. Empirical correlations were developed to estimate the change in hydraulic conductivity given the initial permeability and select crushing parameter values at the stress level of interest. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2844 [...] [article] Influence of particle properties and initial specimen state on one-dimensional compression and hydraulic conductivity [texte imprimé] / Jason T. DeJong, Auteur ; G. Geoffrey Christoph, Auteur . - 2009 . - pp. 449–454.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 449–454
Mots-clés : Crushing Hydraulic conductivity Compression Sand Particles Résumé : Particle crushing can adversely affect geotechnical system performance; examples include clogging in wells, pile shaft capacity degradation, and postconstruction settlements. The generation of fines results in volumetric compression and a reduction hydraulic conductivity, which is important for geotechnical systems whose performance is directly dependent on pore pressure dissipation, groundwater flow, or hydraulic pumping. Knowledge of hydraulic conductivity change is poorly understood due to limited experimental data, and an ability to predict this change is lacking. The role of single particle properties, initial specimen state conditions, and loading conditions on the evolution of hydraulic conductivity with particle crushing was examined experimentally. Specimen response exhibited an overshoot behavior and the convergence to a unique condition independent of initial relative density, gradation, and particle shape. The hydraulic conductivity decreased by 2–3 times before specimen yield, and by 2–3 orders of magnitude after specimen yield. Empirical correlations were developed to estimate the change in hydraulic conductivity given the initial permeability and select crushing parameter values at the stress level of interest. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2844 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 455–458
Titre : Two approaches of finite-element modeling of ballasted railway track Type de document : texte imprimé Auteurs : Chen-Ming Kuo, Auteur ; Cheng-Hao Huang, Auteur Année de publication : 2009 Article en page(s) : pp. 455–458 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Finite element method Ballast Vibration Parameters Résumé : Use of a ballast is still popular in railway engineering due to its resilience, relatively low noise, and convenience in construction and maintenance. The ballast layer was modeled with two modeling approaches in this study–continuous elastic solid and spring-connected elements. Two-dimensional finite element models were built. The parameters of ballast layers were correlated between two models to assure comparability. Three levels of vehicle moving speed were analyzed with the models. Significant differences of rail deflection and ballast were found in all speed levels. Vibration spectra were also compared to reveal the characteristics of different finite element models. It was found that the model with spring-connected discrete elements had higher characteristic frequency than the simple ballast model. Increasing speed may significantly increase rail deflections and ballast vibration levels and result in particles movements in the ballast layer. A thorough understanding of model characteristics and engineering problems is crucial to choose the most appropriate model. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2845 [...] [article] Two approaches of finite-element modeling of ballasted railway track [texte imprimé] / Chen-Ming Kuo, Auteur ; Cheng-Hao Huang, Auteur . - 2009 . - pp. 455–458.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 455–458
Mots-clés : Finite element method Ballast Vibration Parameters Résumé : Use of a ballast is still popular in railway engineering due to its resilience, relatively low noise, and convenience in construction and maintenance. The ballast layer was modeled with two modeling approaches in this study–continuous elastic solid and spring-connected elements. Two-dimensional finite element models were built. The parameters of ballast layers were correlated between two models to assure comparability. Three levels of vehicle moving speed were analyzed with the models. Significant differences of rail deflection and ballast were found in all speed levels. Vibration spectra were also compared to reveal the characteristics of different finite element models. It was found that the model with spring-connected discrete elements had higher characteristic frequency than the simple ballast model. Increasing speed may significantly increase rail deflections and ballast vibration levels and result in particles movements in the ballast layer. A thorough understanding of model characteristics and engineering problems is crucial to choose the most appropriate model. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2845 [...]
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