Documents disponibles écrits par cet auteur

Arching in distribution of active load on retaining walls / Srinivasa S. Nadukuru in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 5 (Mai 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 5 (Mai 2012) . - pp. 575–584 Titre : Arching in distribution of active load on retaining walls Type de document : texte imprimé Auteurs : Srinivasa S. Nadukuru, Auteur ; Radoslaw L. Michalowski, Auteur Année de publication : 2012 Article en page(s) : pp. 575–584 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Arching  Retaining  walls  Active  load  Numerical  analysis  Discrete  element  method Résumé : Traditional methods for calculations of active loads on retaining structures provide dependable forces, but these methods do not indicate reliably the location of the resultant load on the walls. The Coulomb method does not address the load distribution because it utilizes equilibrium of forces, whereas the Rankine stress distribution provides linear increase of the load with depth. Past experimental studies indicate intricate distributions dependent on the mode of displacement of the wall before reaching the limit state. The discrete element method was used to simulate soil-retaining structure interaction, and force chains characteristic of arching were identified. Arching appears to be the primary cause affecting the load distribution. A differential slice technique was used to mimic the load distributions seen in physical experiments. The outcome indicates that rotation modes of wall movement are associated with uneven mobilization of strength on the surface separating the moving backfill from the soil at rest. Calculations show that the location of the centroid of the active load distribution behind a translating wall is approximately 0.40 of the wall height above the base, but for a wall rotating about its top point, the location of the resultant is at approximately 0.55H. In the third case, rotation about the base, the location of the calculated centroid of the stress distribution on the wall is slightly below one-third of the wall height. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000617 [article] Arching in distribution of active load on retaining walls [texte imprimé] / Srinivasa S. Nadukuru, Auteur ; Radoslaw L. Michalowski, Auteur . - 2012 . - pp. 575–584. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 5 (Mai 2012) . - pp. 575–584 Mots-clés : Arching  Retaining  walls  Active  load  Numerical  analysis  Discrete  element  method Résumé : Traditional methods for calculations of active loads on retaining structures provide dependable forces, but these methods do not indicate reliably the location of the resultant load on the walls. The Coulomb method does not address the load distribution because it utilizes equilibrium of forces, whereas the Rankine stress distribution provides linear increase of the load with depth. Past experimental studies indicate intricate distributions dependent on the mode of displacement of the wall before reaching the limit state. The discrete element method was used to simulate soil-retaining structure interaction, and force chains characteristic of arching were identified. Arching appears to be the primary cause affecting the load distribution. A differential slice technique was used to mimic the load distributions seen in physical experiments. The outcome indicates that rotation modes of wall movement are associated with uneven mobilization of strength on the surface separating the moving backfill from the soil at rest. Calculations show that the location of the centroid of the active load distribution behind a translating wall is approximately 0.40 of the wall height above the base, but for a wall rotating about its top point, the location of the resultant is at approximately 0.55H. In the third case, rotation about the base, the location of the calculated centroid of the stress distribution on the wall is slightly below one-third of the wall height. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000617

Static fatigue, time effects, and delayed increase in penetration resistance after dynamic compaction of sands / Radoslaw L. Michalowski in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 5 (Mai 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 5 (Mai 2012) . - pp. 564–574 Titre : Static fatigue, time effects, and delayed increase in penetration resistance after dynamic compaction of sands Type de document : texte imprimé Auteurs : Radoslaw L. Michalowski, Auteur ; Srinivasa S. Nadukuru, Auteur Année de publication : 2012 Article en page(s) : pp. 564–574 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Sand  behavior  Dynamic  compaction  Static  fatigue  Stress  corrosion  cracking  Micro-fracturing  Grain  convergence  Multiscale  analysis  Static  cone  penetration  Sand  aging  Discrete  element  simulations Résumé : Dynamically compacted sands often exhibit a drop in cone penetration resistance immediately after compaction, but a gradual increase in the resistance occurs in a matter of weeks and months. An explanation of the former is sought in analysis of the stress state immediately after a dynamic disturbance, and a justification for the latter is found in the micromechanics process of static fatigue (or stress corrosion cracking) of the micromorphologic features at the contacts between sand grains. The delayed fracturing of contact asperities leads to grain convergence, followed by an increase in contact stiffness and an increase in elastic modulus of sand at the macroscopic scale. Time-dependent increase in small-strain stiffness of sand under a sustained load is a phenomenon confirmed by earlier experiments. It is argued that the initial drop in the cone penetration resistance after dynamic compaction is caused by a drop in the horizontal stress after the disturbance. The subsequent gradual increase in the penetration resistance is not a result of increasing strength, but it is owed to the time-delayed increase in stiffness of sand, causing increase in horizontal stress under one-dimensional strain conditions. This process is a consequence of static fatigue at contacts between grains. The strength of sand after dynamic compaction increases as soon as the fabric of the compacted sand is formed and is little affected by the process of grain convergence in the time after compaction. Contact stiffness, with its dependence on static fatigue, holds information about the previous loading process, and it is a memory parameter of a kind; this information is lost after a disturbance, such as dynamic compaction, in which new contacts are formed. The scanning electron microscope (SEM) observations, discrete element simulations, and energy considerations are carried out to make the argument for the proposed hypothesis stronger. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000611 [article] Static fatigue, time effects, and delayed increase in penetration resistance after dynamic compaction of sands [texte imprimé] / Radoslaw L. Michalowski, Auteur ; Srinivasa S. Nadukuru, Auteur . - 2012 . - pp. 564–574. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 5 (Mai 2012) . - pp. 564–574 Mots-clés : Sand  behavior  Dynamic  compaction  Static  fatigue  Stress  corrosion  cracking  Micro-fracturing  Grain  convergence  Multiscale  analysis  Static  cone  penetration  Sand  aging  Discrete  element  simulations Résumé : Dynamically compacted sands often exhibit a drop in cone penetration resistance immediately after compaction, but a gradual increase in the resistance occurs in a matter of weeks and months. An explanation of the former is sought in analysis of the stress state immediately after a dynamic disturbance, and a justification for the latter is found in the micromechanics process of static fatigue (or stress corrosion cracking) of the micromorphologic features at the contacts between sand grains. The delayed fracturing of contact asperities leads to grain convergence, followed by an increase in contact stiffness and an increase in elastic modulus of sand at the macroscopic scale. Time-dependent increase in small-strain stiffness of sand under a sustained load is a phenomenon confirmed by earlier experiments. It is argued that the initial drop in the cone penetration resistance after dynamic compaction is caused by a drop in the horizontal stress after the disturbance. The subsequent gradual increase in the penetration resistance is not a result of increasing strength, but it is owed to the time-delayed increase in stiffness of sand, causing increase in horizontal stress under one-dimensional strain conditions. This process is a consequence of static fatigue at contacts between grains. The strength of sand after dynamic compaction increases as soon as the fabric of the compacted sand is formed and is little affected by the process of grain convergence in the time after compaction. Contact stiffness, with its dependence on static fatigue, holds information about the previous loading process, and it is a memory parameter of a kind; this information is lost after a disturbance, such as dynamic compaction, in which new contacts are formed. The scanning electron microscope (SEM) observations, discrete element simulations, and energy considerations are carried out to make the argument for the proposed hypothesis stronger. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000611