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Détails du magazine
Format
Magazine
eISSN
2083-831X
ISSN
0137-6365
Première publication
09 Nov 2012
Période de publication
4 fois par an
Langues
Anglais

Chercher

Volume 36 (2014): Edition 4 (December 2014)

Détails du magazine
Format
Magazine
eISSN
2083-831X
ISSN
0137-6365
Première publication
09 Nov 2012
Période de publication
4 fois par an
Langues
Anglais

Chercher

8 Articles
Accès libre

The Effect of 200 MPa Pressure on Specific Surface Area of Clay

Publié en ligne: 28 Feb 2015
Pages: 3 - 6

Résumé

Abstract

The paper presents the results of laboratory studies of the 200 MPa pressure effect on specific surface area of clay. The original high-pressure investigation stand was used for the pressure tests. Determination of the specific surface area was performed by the methylene blue adsorption method. The results of the specific surface area test were compared for non-pressurized clays and for clays pressured in a high-pressure chamber. It was found that the specific surface area of pressurized soil clearly increased. This shows that some microstructural changes take place in the soil skeleton of clays.

Mots clés

  • clay
  • high pressure
  • specific surface area
  • microstructural changes
Accès libre

Comparative Model Tests of SDP and CFA Pile Groups in Non-Cohesive Soil

Publié en ligne: 28 Feb 2015
Pages: 7 - 11

Résumé

Abstract

The research topic relates to the subject of deep foundations supported on continuous flight auger (CFA) piles and screw displacement piles (SDP). The authors have decided to conduct model tests of foundations supported on the group of piles mentioned above and also the tests of the same piles working as a single. The tests are ongoing in Geotechnical Laboratory of Gdaňsk University of Technology. The description of test procedure, interpretation and analysis of the preliminary testing series results are presented in the paper.

Mots clés

  • CFA piles
  • screw displacement piles
  • deep foundation
  • model tests
  • group of piles
Accès libre

Dynamic Response of Three-Layered Annular Plate with Imperfections

Publié en ligne: 28 Feb 2015
Pages: 13 - 25

Résumé

Abstract

This paper presents the imperfection sensitivity of annular plate with three-layered structure. The plate composed of thin elastic facings and a thicker elastic core is loaded in facing plane. The classical issue of a three-layered plate was solved for dynamic deflection problem using the approximation methods: orthogonalization and finite difference. The solution includes the axisymmetric and asymmetric plate modes of the dynamic stability loss. The evaluation of the rate of plate sensitivity to imperfection of plate preliminary geometry has been enriched by the analysis of plate models built of finite elements. The ABAQUS program has been used. The numerous calculation results in the form of deflection characteristics, buckling modes, values of critical parameters create the view of response of dynamic plate structure with different rate of imperfection and linear in time loading growth, too.

Mots clés

  • sandwich
  • annular plate
  • dynamic stability
  • imperfections
  • finite difference method,
  • finite element method
Accès libre

Modeling of Fracture Propagation in Concrete Structures Using a Constitutive Relation with Embedded Discontinuity

Publié en ligne: 28 Feb 2015
Pages: 27 - 33

Résumé

Abstract

In this paper, the problem of modeling of mixed mode cracking in concrete structures is addressed within the context of a constitutive law with embedded discontinuity (CLED). This approach, which was originally developed for describing the propagation of localized deformation in a “smeared” sense, is enhanced here to model a discrete nature of crack propagation. The latter is achieved by coupling the CLED approach with the level-set method, which is commonly used within the framework of Extended Finite Element (XFEM). Numerical simulations of experimental tests conducted at Delft University, which involve four-point bending of a notched concrete beam under the action of two independent actuators, are presented. The results based on enhanced CLED approach are directly compared with XFEM simulations. The predictions from both these methodologies are quite consistent with the experimental data, thereby giving advantage to CLED scheme in view of its simplicity in the numerical implementation.

Mots clés

  • XFEM
  • embedded discontinuity model
  • level set method
  • cohesive crack propagation
Accès libre

Structure and Calibration of Constitutive Equations for Granular Soils

Publié en ligne: 28 Feb 2015
Pages: 35 - 46

Résumé

Abstract

The form of incremental constitutive equations for granular soils is discussed for the triaxial configuration. The classical elasto-plastic approach and the semi-empirical model are discussed on the basis of constitutive relations determined directly from experimental data. First, the general structure of elasto-plastic constitutive equations is presented. Then, the structure of semiempirical constitutive equations is described, and a method of calibrating the model is presented. This calibration method is based on a single experiment, performed in the triaxial apparatus, which also involves a partial verification of the model, on an atypical stress path. The model is shown to give reasonable predictions. An important feature of the semi-empirical incremental model is the definition of loading and unloading, which is different from that assumed in elasto-plasticity. This definition distinguishes between spherical and deviatoric loading/unloading. The definition of deviatoric loading/unloading has been subject to some criticism. It was therefore discussed and clarified in this paper on the basis of the experiment presented.

Mots clés

  • granular soil
  • constitutive equations
  • triaxial conditions
  • pre-failure deformations
Accès libre

X-Ray Microtomography (μCT) as a Useful Tool for Visualization and Interpretation of Shear Strength Test Results

Publié en ligne: 28 Feb 2015
Pages: 47 - 55

Résumé

Abstract

The paper demonstrates the applicability of X-ray microtomography (ìCT) to analysis of the results of shear strength examinations of clayey soils. The method of X-ray three-dimensional imaging offers new possibilities in soil testing. The work focuses on a non-destructive method of evaluation of specimen quality used in shear tests and mechanical behavior of soil. The paper presents the results of examination of 4 selected clayey soils. Specimens prepared for the triaxial test have been scanned using ìCT before and after the triaxial compression tests. The shear strength parameters of the soils have been estimated. Changes in soil structure caused by compression and shear failure have been presented as visualizations of the samples tested. This allowed for improved interpretation and evaluation of soil strength parameters and recognition of pre-existing fissures and the exact mode of failure. Basic geometrical parameters have been determined for selected cross-sections of specimens after failure. The test results indicate the utility of the method applied in soil testing.

Mots clés

  • X-ray microtomography
  • shear strength
  • shear plane
  • fine-grained soil
  • triaxial test
Accès libre

Random Vortex Method in Numerical Analysis of 2D Flow Around Circular Cylinder

Publié en ligne: 28 Feb 2015
Pages: 57 - 63

Résumé

Abstract

A combination of the vortex method and the boundary element method is used here to predict the two-dimensional flow field around a circular cylinder. Cylindrical structures experience strong hydrodynamic loading, due to vortex detachment from the both sides of cylinder during the flow. Thus, the practical meaning of such calculation is significant particularly in offshore oil and gas engineering as well as in the bridge and hydraulic structure engineering. This paper presents the mathematical formulation of the vortex method for the velocity and vorticity field calculation. The calculated velocity and vorticity fields are then used to predict the pressure distribution on the cylinder surface by the boundary element method. The resulting pressure on the cylinder, the Strouhal number and the length of the base recirculation zone are compared with solutions of other numerical methods and experiments, and a good agreement is achieved.

Mots clés

  • vorticity
  • vortex method
  • flow instability
  • circular cylinder
  • boundary element method
Accès libre

Technical Note: Stability of a Levee Made of Bottom Sediments From a Dam Reservoir

Publié en ligne: 28 Feb 2015
Pages: 65 - 70

Résumé

Abstract

Stability analysis of a levee made of the bottom sediments from Czorsztyn-Niedzica Reservoir is presented in the paper. These sediments were classified as silty sands and, based on the authors' own research, their geotechnical parameters were beneficial, so the possibility of using this material for the hydraulic embankments was considered. Stability and filtration calculations were carried out for a levee that had the same top width - 3 m, slope inclinations 1:2 and different heights: 4, 6 and 8 m. Two methods were used: analytical and numerical. Calculations were carried out without and with a steady and unsteady seepage filtration. Based on the analysis carried out it was stated that the levee made of the bottom sediments is stable even at the height of 8.0 m, although because of the seepage on the downstream side it is recommended to use a drainage at the toe of the slope.

Mots clés

  • bottom sediments
  • hydraulic embankments
  • stability
8 Articles
Accès libre

The Effect of 200 MPa Pressure on Specific Surface Area of Clay

Publié en ligne: 28 Feb 2015
Pages: 3 - 6

Résumé

Abstract

The paper presents the results of laboratory studies of the 200 MPa pressure effect on specific surface area of clay. The original high-pressure investigation stand was used for the pressure tests. Determination of the specific surface area was performed by the methylene blue adsorption method. The results of the specific surface area test were compared for non-pressurized clays and for clays pressured in a high-pressure chamber. It was found that the specific surface area of pressurized soil clearly increased. This shows that some microstructural changes take place in the soil skeleton of clays.

Mots clés

  • clay
  • high pressure
  • specific surface area
  • microstructural changes
Accès libre

Comparative Model Tests of SDP and CFA Pile Groups in Non-Cohesive Soil

Publié en ligne: 28 Feb 2015
Pages: 7 - 11

Résumé

Abstract

The research topic relates to the subject of deep foundations supported on continuous flight auger (CFA) piles and screw displacement piles (SDP). The authors have decided to conduct model tests of foundations supported on the group of piles mentioned above and also the tests of the same piles working as a single. The tests are ongoing in Geotechnical Laboratory of Gdaňsk University of Technology. The description of test procedure, interpretation and analysis of the preliminary testing series results are presented in the paper.

Mots clés

  • CFA piles
  • screw displacement piles
  • deep foundation
  • model tests
  • group of piles
Accès libre

Dynamic Response of Three-Layered Annular Plate with Imperfections

Publié en ligne: 28 Feb 2015
Pages: 13 - 25

Résumé

Abstract

This paper presents the imperfection sensitivity of annular plate with three-layered structure. The plate composed of thin elastic facings and a thicker elastic core is loaded in facing plane. The classical issue of a three-layered plate was solved for dynamic deflection problem using the approximation methods: orthogonalization and finite difference. The solution includes the axisymmetric and asymmetric plate modes of the dynamic stability loss. The evaluation of the rate of plate sensitivity to imperfection of plate preliminary geometry has been enriched by the analysis of plate models built of finite elements. The ABAQUS program has been used. The numerous calculation results in the form of deflection characteristics, buckling modes, values of critical parameters create the view of response of dynamic plate structure with different rate of imperfection and linear in time loading growth, too.

Mots clés

  • sandwich
  • annular plate
  • dynamic stability
  • imperfections
  • finite difference method,
  • finite element method
Accès libre

Modeling of Fracture Propagation in Concrete Structures Using a Constitutive Relation with Embedded Discontinuity

Publié en ligne: 28 Feb 2015
Pages: 27 - 33

Résumé

Abstract

In this paper, the problem of modeling of mixed mode cracking in concrete structures is addressed within the context of a constitutive law with embedded discontinuity (CLED). This approach, which was originally developed for describing the propagation of localized deformation in a “smeared” sense, is enhanced here to model a discrete nature of crack propagation. The latter is achieved by coupling the CLED approach with the level-set method, which is commonly used within the framework of Extended Finite Element (XFEM). Numerical simulations of experimental tests conducted at Delft University, which involve four-point bending of a notched concrete beam under the action of two independent actuators, are presented. The results based on enhanced CLED approach are directly compared with XFEM simulations. The predictions from both these methodologies are quite consistent with the experimental data, thereby giving advantage to CLED scheme in view of its simplicity in the numerical implementation.

Mots clés

  • XFEM
  • embedded discontinuity model
  • level set method
  • cohesive crack propagation
Accès libre

Structure and Calibration of Constitutive Equations for Granular Soils

Publié en ligne: 28 Feb 2015
Pages: 35 - 46

Résumé

Abstract

The form of incremental constitutive equations for granular soils is discussed for the triaxial configuration. The classical elasto-plastic approach and the semi-empirical model are discussed on the basis of constitutive relations determined directly from experimental data. First, the general structure of elasto-plastic constitutive equations is presented. Then, the structure of semiempirical constitutive equations is described, and a method of calibrating the model is presented. This calibration method is based on a single experiment, performed in the triaxial apparatus, which also involves a partial verification of the model, on an atypical stress path. The model is shown to give reasonable predictions. An important feature of the semi-empirical incremental model is the definition of loading and unloading, which is different from that assumed in elasto-plasticity. This definition distinguishes between spherical and deviatoric loading/unloading. The definition of deviatoric loading/unloading has been subject to some criticism. It was therefore discussed and clarified in this paper on the basis of the experiment presented.

Mots clés

  • granular soil
  • constitutive equations
  • triaxial conditions
  • pre-failure deformations
Accès libre

X-Ray Microtomography (μCT) as a Useful Tool for Visualization and Interpretation of Shear Strength Test Results

Publié en ligne: 28 Feb 2015
Pages: 47 - 55

Résumé

Abstract

The paper demonstrates the applicability of X-ray microtomography (ìCT) to analysis of the results of shear strength examinations of clayey soils. The method of X-ray three-dimensional imaging offers new possibilities in soil testing. The work focuses on a non-destructive method of evaluation of specimen quality used in shear tests and mechanical behavior of soil. The paper presents the results of examination of 4 selected clayey soils. Specimens prepared for the triaxial test have been scanned using ìCT before and after the triaxial compression tests. The shear strength parameters of the soils have been estimated. Changes in soil structure caused by compression and shear failure have been presented as visualizations of the samples tested. This allowed for improved interpretation and evaluation of soil strength parameters and recognition of pre-existing fissures and the exact mode of failure. Basic geometrical parameters have been determined for selected cross-sections of specimens after failure. The test results indicate the utility of the method applied in soil testing.

Mots clés

  • X-ray microtomography
  • shear strength
  • shear plane
  • fine-grained soil
  • triaxial test
Accès libre

Random Vortex Method in Numerical Analysis of 2D Flow Around Circular Cylinder

Publié en ligne: 28 Feb 2015
Pages: 57 - 63

Résumé

Abstract

A combination of the vortex method and the boundary element method is used here to predict the two-dimensional flow field around a circular cylinder. Cylindrical structures experience strong hydrodynamic loading, due to vortex detachment from the both sides of cylinder during the flow. Thus, the practical meaning of such calculation is significant particularly in offshore oil and gas engineering as well as in the bridge and hydraulic structure engineering. This paper presents the mathematical formulation of the vortex method for the velocity and vorticity field calculation. The calculated velocity and vorticity fields are then used to predict the pressure distribution on the cylinder surface by the boundary element method. The resulting pressure on the cylinder, the Strouhal number and the length of the base recirculation zone are compared with solutions of other numerical methods and experiments, and a good agreement is achieved.

Mots clés

  • vorticity
  • vortex method
  • flow instability
  • circular cylinder
  • boundary element method
Accès libre

Technical Note: Stability of a Levee Made of Bottom Sediments From a Dam Reservoir

Publié en ligne: 28 Feb 2015
Pages: 65 - 70

Résumé

Abstract

Stability analysis of a levee made of the bottom sediments from Czorsztyn-Niedzica Reservoir is presented in the paper. These sediments were classified as silty sands and, based on the authors' own research, their geotechnical parameters were beneficial, so the possibility of using this material for the hydraulic embankments was considered. Stability and filtration calculations were carried out for a levee that had the same top width - 3 m, slope inclinations 1:2 and different heights: 4, 6 and 8 m. Two methods were used: analytical and numerical. Calculations were carried out without and with a steady and unsteady seepage filtration. Based on the analysis carried out it was stated that the levee made of the bottom sediments is stable even at the height of 8.0 m, although because of the seepage on the downstream side it is recommended to use a drainage at the toe of the slope.

Mots clés

  • bottom sediments
  • hydraulic embankments
  • stability

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