Documents disponibles écrits par cet auteur

Hybrid method for analysis and design of slope stabilizing piles / R. Kourkoulis in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 1 (Janvier 2012) . - pp. 1-14 Titre : Hybrid method for analysis and design of slope stabilizing piles Type de document : texte imprimé Auteurs : R. Kourkoulis, Auteur ; F. Gelagoti, Auteur ; I. Anastasopoulos, Auteur Année de publication : 2012 Article en page(s) : pp. 1-14 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Slope  stability  Soil-structure  interaction  Pile  groups  Validation  against  experiments  Simplified  method  Field  tests Résumé : Piles are extensively used as a means of slope stabilization. Despite the rapid advances in computing and software power, the design of such piles may still include a high degree of conservatism, stemming from the use of simplified, easy-to-apply methodologies. This paper develops a hybrid method for designing slope-stabilizing piles, combining the accuracy of rigorous three-dimensional (3D) finite-element (FE) simulation with the simplicity of widely accepted analytical techniques. It consists of two steps: (1) evaluation of the lateral resisting force (RF) needed to increase the safety factor of the precarious slope to the desired value, and (2) estimation of the optimum pile configuration that offers the required RF for a prescribed deformation level. The first step utilizes the results of conventional slope-stability analysis. A novel approach is proposed for the second step. This consists of decoupling the slope geometry from the computation of pile lateral capacity, which allows numerical simulation of only a limited region of soil around the piles. A comprehensive validation is presented against published experimental, field, and theoretical results from fully coupled 3D nonlinear FE analyses. The proposed method provides a useful, computationally efficient tool for parametric analyses and design of slope-stabilizing piles. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i1/p1_s1?isAuthorized=no [article] Hybrid method for analysis and design of slope stabilizing piles [texte imprimé] / R. Kourkoulis, Auteur ; F. Gelagoti, Auteur ; I. Anastasopoulos, Auteur . - 2012 . - pp. 1-14. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 1 (Janvier 2012) . - pp. 1-14 Mots-clés : Slope  stability  Soil-structure  interaction  Pile  groups  Validation  against  experiments  Simplified  method  Field  tests Résumé : Piles are extensively used as a means of slope stabilization. Despite the rapid advances in computing and software power, the design of such piles may still include a high degree of conservatism, stemming from the use of simplified, easy-to-apply methodologies. This paper develops a hybrid method for designing slope-stabilizing piles, combining the accuracy of rigorous three-dimensional (3D) finite-element (FE) simulation with the simplicity of widely accepted analytical techniques. It consists of two steps: (1) evaluation of the lateral resisting force (RF) needed to increase the safety factor of the precarious slope to the desired value, and (2) estimation of the optimum pile configuration that offers the required RF for a prescribed deformation level. The first step utilizes the results of conventional slope-stability analysis. A novel approach is proposed for the second step. This consists of decoupling the slope geometry from the computation of pile lateral capacity, which allows numerical simulation of only a limited region of soil around the piles. A comprehensive validation is presented against published experimental, field, and theoretical results from fully coupled 3D nonlinear FE analyses. The proposed method provides a useful, computationally efficient tool for parametric analyses and design of slope-stabilizing piles. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i1/p1_s1?isAuthorized=no

Simplified constitutive model for simulation of cyclic response of shallow foundations / I. Anastasopoulos in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 12 (Décembre 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1154-1168 Titre : Simplified constitutive model for simulation of cyclic response of shallow foundations : Validation against laboratory tests Type de document : texte imprimé Auteurs : I. Anastasopoulos, Auteur ; F. Gelagoti, Auteur ; R. Kourkoulis, Auteur Année de publication : 2012 Article en page(s) : pp. 1154-1168 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Rocking  foundation  Numerical  method  Constitutive  relations  Bearing  capacity  Cyclic  response  Centrifuge  experiments  Experimental  validation Résumé : The nonlinear response of shallow foundations has been studied experimentally and analytically. However, the engineering community is not yet convinced of the applicability of such concepts in practice. A key prerequisite is the ability to realistically model such effects. Although several sophisticated constitutive models are readily available in the literature, their use in practice is limited, because (1) they typically require extensive soil testing for calibration; (2) as they are implemented in highly specialized numerical codes, they are usually restricted to simple superstructures; and (3) in most cases, they can only be applied by numerical analysis specialists. Attempting to overcome some of these difficulties, this paper develops a simplified but fairly comprehensive constitutive model for analysis of the cyclic response of shallow foundations. On the basis of a kinematic hardening constitutive model with Von Mises failure criterion (readily available in commercial finite element codes), the model is made pressure sensitive and capable of reproducing both the low-strain stiffness and the ultimate resistance of clays and sands. Encoded in ABAQUS through a simple user subroutine, the model is validated against (a) centrifuge tests of shallow footings on clay under cyclic loading and (b) large-scale tests of a square footing on dense and loose sand under cyclic loading, conducted in the European Laboratory for Structural Analysis for the TRISEE project. The performance of the model is shown to be quite satisfactory, and discrepancies between theory and experiment are discussed and potential culprits are identified. Requiring calibration of only two parameters and being easily implemented in commercial FE codes, the model is believed to provide an easily applicable engineering solution. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i12/p1154_s1?isAuthorized=no [article] Simplified constitutive model for simulation of cyclic response of shallow foundations : Validation against laboratory tests [texte imprimé] / I. Anastasopoulos, Auteur ; F. Gelagoti, Auteur ; R. Kourkoulis, Auteur . - 2012 . - pp. 1154-1168. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1154-1168 Mots-clés : Rocking  foundation  Numerical  method  Constitutive  relations  Bearing  capacity  Cyclic  response  Centrifuge  experiments  Experimental  validation Résumé : The nonlinear response of shallow foundations has been studied experimentally and analytically. However, the engineering community is not yet convinced of the applicability of such concepts in practice. A key prerequisite is the ability to realistically model such effects. Although several sophisticated constitutive models are readily available in the literature, their use in practice is limited, because (1) they typically require extensive soil testing for calibration; (2) as they are implemented in highly specialized numerical codes, they are usually restricted to simple superstructures; and (3) in most cases, they can only be applied by numerical analysis specialists. Attempting to overcome some of these difficulties, this paper develops a simplified but fairly comprehensive constitutive model for analysis of the cyclic response of shallow foundations. On the basis of a kinematic hardening constitutive model with Von Mises failure criterion (readily available in commercial finite element codes), the model is made pressure sensitive and capable of reproducing both the low-strain stiffness and the ultimate resistance of clays and sands. Encoded in ABAQUS through a simple user subroutine, the model is validated against (a) centrifuge tests of shallow footings on clay under cyclic loading and (b) large-scale tests of a square footing on dense and loose sand under cyclic loading, conducted in the European Laboratory for Structural Analysis for the TRISEE project. The performance of the model is shown to be quite satisfactory, and discrepancies between theory and experiment are discussed and potential culprits are identified. Requiring calibration of only two parameters and being easily implemented in commercial FE codes, the model is believed to provide an easily applicable engineering solution. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i12/p1154_s1?isAuthorized=no

Slope stabilizing piles and pile-groups / R. Kourkoulis in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 7 (Juillet 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 7 (Juillet 2011) . - pp. 663-677 Titre : Slope stabilizing piles and pile-groups : parametric Study and Design Insights Type de document : texte imprimé Auteurs : R. Kourkoulis, Auteur ; F. Gelagoti, Auteur ; I. Anastasopoulos, Auteur Année de publication : 2011 Article en page(s) : pp. 663-677 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Slope  stabilizing  piles  Embedment  depth  Simplified  method  Dimensionless  charts  Arching  Pile  groups Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : This paper uses a hybrid method for analysis and design of slope stabilizing piles that was developed in a preceding paper by the writers. The aim of this paper is to derive insights about the factors influencing the response of piles and pile-groups. Axis-to-axis pile spacing (S), thickness of stable soil mass (Hu), depth (Le) of pile embedment, pile diameter (D), and pile group configuration are the parameters addressed in the study. It is shown that S = 4D is the most cost-effective pile spacing, because it is the largest spacing that can still generate soil arching between the piles. Soil inhomogeneity (in terms of shear stiffness) was found to be unimportant, because the response is primarily affected by the strength of the unstable soil layer. For relatively small pile embedments, pile response is dominated by rigid-body rotation without substantial flexural distortion: the short pile mode of failure. In these cases, the structural capacity of the pile cannot be exploited, and the design will not be economical. The critical embedment depth to achieve fixity conditions at the base of the pile is found to range from 0.7Hu to 1.5Hu, depending on the relative strength of the unstable ground compared to that of the stable ground (i.e., the soil below the sliding plane). An example of dimensionless design charts is presented for piles embedded in rock. Results are presented for two characteristic slenderness ratios and several pile spacings. Single piles are concluded to be generally inadequate for stabilizing deep landslides, although capped pile-groups invoking framing action may offer an efficient solution. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i7/p663_s1?isAuthorized=no [article] Slope stabilizing piles and pile-groups : parametric Study and Design Insights [texte imprimé] / R. Kourkoulis, Auteur ; F. Gelagoti, Auteur ; I. Anastasopoulos, Auteur . - 2011 . - pp. 663-677. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 7 (Juillet 2011) . - pp. 663-677 Mots-clés : Slope  stabilizing  piles  Embedment  depth  Simplified  method  Dimensionless  charts  Arching  Pile  groups Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : This paper uses a hybrid method for analysis and design of slope stabilizing piles that was developed in a preceding paper by the writers. The aim of this paper is to derive insights about the factors influencing the response of piles and pile-groups. Axis-to-axis pile spacing (S), thickness of stable soil mass (Hu), depth (Le) of pile embedment, pile diameter (D), and pile group configuration are the parameters addressed in the study. It is shown that S = 4D is the most cost-effective pile spacing, because it is the largest spacing that can still generate soil arching between the piles. Soil inhomogeneity (in terms of shear stiffness) was found to be unimportant, because the response is primarily affected by the strength of the unstable soil layer. For relatively small pile embedments, pile response is dominated by rigid-body rotation without substantial flexural distortion: the short pile mode of failure. In these cases, the structural capacity of the pile cannot be exploited, and the design will not be economical. The critical embedment depth to achieve fixity conditions at the base of the pile is found to range from 0.7Hu to 1.5Hu, depending on the relative strength of the unstable ground compared to that of the stable ground (i.e., the soil below the sliding plane). An example of dimensionless design charts is presented for piles embedded in rock. Results are presented for two characteristic slenderness ratios and several pile spacings. Single piles are concluded to be generally inadequate for stabilizing deep landslides, although capped pile-groups invoking framing action may offer an efficient solution. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i7/p663_s1?isAuthorized=no