Magazine et Edition

AHEAD OF PRINT

Volume 44 (2022): Edition 3 (September 2022)

Volume 44 (2022): Edition 2 (June 2022)

Volume 44 (2022): Edition 1 (March 2022)

Volume 43 (2021): Edition 4 (December 2021)

Volume 43 (2021): Edition 3 (September 2021)

Volume 43 (2021): Edition 2 (June 2021)

Volume 43 (2021): Edition s1 (December 2021)
Special Edition: Underground Infrastructure of Urban Areas

Volume 43 (2021): Edition 1 (April 2021)

Volume 42 (2020): Edition 4 (December 2020)

Volume 42 (2020): Edition 3 (September 2020)

Volume 42 (2020): Edition 2 (June 2020)

Volume 42 (2020): Edition 1 (April 2020)

Volume 41 (2019): Edition 4 (December 2019)

Volume 41 (2019): Edition 3 (September 2019)

Volume 41 (2019): Edition 2 (June 2019)

Volume 41 (2019): Edition 1 (April 2019)

Volume 40 (2018): Edition 4 (December 2018)

Volume 40 (2018): Edition 3 (November 2018)

Volume 40 (2018): Edition 2 (October 2018)

Volume 40 (2018): Edition 1 (July 2018)

Volume 39 (2017): Edition 4 (December 2017)

Volume 39 (2017): Edition 3 (September 2017)

Volume 39 (2017): Edition 2 (June 2017)

Volume 39 (2017): Edition 1 (March 2017)

Volume 38 (2016): Edition 4 (December 2016)

Volume 38 (2016): Edition 3 (September 2016)

Volume 38 (2016): Edition 2 (June 2016)

Volume 38 (2016): Edition 1 (March 2016)

Volume 37 (2015): Edition 4 (December 2015)

Volume 37 (2015): Edition 3 (September 2015)

Volume 37 (2015): Edition 2 (June 2015)

Volume 37 (2015): Edition 1 (March 2015)

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

Volume 36 (2014): Edition 3 (September 2014)

Volume 36 (2014): Edition 2 (June 2014)

Volume 36 (2014): Edition 1 (March 2014)

Volume 35 (2013): Edition 4 (December 2013)

Volume 35 (2013): Edition 3 (September 2013)

Volume 35 (2013): Edition 2 (June 2013)

Volume 35 (2013): Edition 1 (March 2013)

Volume 34 (2012): Edition 4 (December 2012)

Volume 34 (2012): Edition 3 (September 2012)

Volume 34 (2012): Edition 2 (June 2012)

Volume 34 (2012): Edition 1 (March 2012)

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

Chercher

Volume 42 (2020): Edition 2 (June 2020)

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

Chercher

6 Articles

Research Articles

Accès libre

Modelling the time-dependent behaviour of soft soils

Publié en ligne: 30 Jun 2020
Pages: 97 - 110

Résumé

Abstract

Time dependence of soft soils has already been thoroughly investigated. The knowledge on creep and relaxation phenomena is generally available in the literature. However, it is still rarely applied in practice. Regarding the organic soils, geotechnical engineers mostly base their calculations on the simple assumptions. Yet, as presented within this article, the rate-dependent behaviour of soft soils is a very special and important feature. It influences both the strength and the stiffness of a soil depending on time. It is, thus, significant to account for time dependence in the geotechnical design when considering the soft soils. This can result in a more robust and economic design of geotechnical structures. Hence, the up-to-date possibilities of regarding creep in practice, which are provided by the existing theories, are reviewed herein.

In this article, we first justify the importance of creep effects in practical applications. Next, we present the fundamental theories explaining the time-dependent behaviour of organic soils. Finally, the revision of the existing constitutive models that can be used in numerical simulations involving soft soils is introduced. Both the models that are implemented in the commercial geotechnical software and some more advanced models that take into account further aspects of soft soils behaviour are revised. The assumptions, the basic equations along with the advantages and the drawbacks of the considered models are described.

Mots clés

  • creep
  • soft soil
  • normally consolidated soils
  • elasto-viscoplastic model
Accès libre

An influence of track stiffness discontinuity on pantograph base vibrations and catenary–pantograph dynamic interaction

Publié en ligne: 30 Jun 2020
Pages: 111 - 124

Résumé

Abstract

In this article, the computational methodology of the catenary–train–track system vibration analysis is presented and used to estimate the influence of vehicle body vibrations on the pantograph–catenary dynamic interaction. This issue is rarely referred in the literature, although any perturbations appearing at the pantograph–catenary interface are of great importance for high-speed railways. Vehicle body vibrations considered in this article are induced by the passage of train through the track stiffness discontinuity, being a frequent cause of significant dynamic effects. First, the most important assumptions of the computational model are presented, including the general idea of decomposing catenary–train–track dynamic system into two main subsystems and the concept of one-way coupling between them. Then, the pantograph base vibrations calculated for two train speeds (60 m/s, 100 m/s) and two cases of track discontinuity (a sudden increase and a sudden decrease in the stiffness of track substrate) are analyzed. Two cases of the railway vehicle suspension are considered – a typical two-stage suspension and a primary suspension alone. To evaluate catenary–pantograph dynamic interaction, the dynamic uplift of the contact wire at steady arm and the pantograph contact force is computed. It is demonstrated that an efficiency of the two-stage suspension grows with the train speed; hence, such vehicle suspension effectively suppresses strong sudden shocks of vehicle body, appearing while the train passes through the track stiffness discontinuity at a high speed. In a hypothetical case when the one-stage vehicle suspension is used, the pantograph base vibrations may increase the number of contact loss events at the catenary–pantograph interface.

Mots clés

  • catenary–train–track system
  • track stiffness discontinuity
  • railway vehicle suspension
  • vibration simulations
  • catenary–pantograph dynamic interaction
Accès libre

On determining the undrained bearing capacity coefficients of variation for foundations embedded on spatially variable soil

Publié en ligne: 30 Jun 2020
Pages: 125 - 136

Résumé

Abstract

This paper presents an efficient method and its usage for the three-dimensional random bearing capacity evaluation for square and rectangular footings. One of the objectives of the study is to deliver graphs that can be used to easily estimate the approximated values of coefficients of variations of undrained bearing capacity. The numerical calculations were based on the proposed method that connects three-dimensional failure mechanism, simulated annealing optimization scheme and spatial averaging. The random field is used for describing the spatial variability of undrained shear strength. The proposed approach is in accordance with a constant covariance matrix concept, that results in a highly efficient tool for estimating the probabilistic characteristics of bearing capacity. As a result, numerous three-dimensional simulations were performed to create the graphs. The considered covariance matrix is a result of Vanmarcke’s spatial averaging discretization of a random field in the dissipation regions to the single random variables. The matrix describes mutual correlation between each dissipation region (or between those random variables). However, in the presented approach, the matrix was obtained for the expected value of undrained shear strength and keep constant during Monte Carlo simulations. The graphs were established in dimensionless coordinates that vary in the observable in practice ranges of parameters (i.e., values of fluctuation scales, foundation sizes and shapes). Examples of usage were given in the study to illustrate the application possibility of the graphs. Moreover, the comparison with the approach that uses individually determined covariance matrix is shown.

Mots clés

  • Spatial averaging
  • random fields
  • random bearing capacity
  • fluctuation scale
  • failure mechanism
Accès libre

Deformations and stability of granular soils: Classical triaxial tests and numerical results from an incremental model

Publié en ligne: 30 Jun 2020
Pages: 137 - 150

Résumé

Abstract

This article presents a modified incremental model describing pre-failure deformations of granular soils under classical triaxial conditions. The original shape of equations has been proposed by Sawicki and Świdziński [40, 41]. A new form of equations that are consistent with the proposed definitions of deviatoric loading and unloading is suggested. Triaxial tests necessary for calibrating the proposed model have been performed. The modified model is used to simulate the deformations and stability of sand for every pre-failure loading path and makes it possible to describe the behaviour of granular soil under both drained and undrained conditions.

A comparison of experimental and numerical results is presented. All investigations were performed in a classical tri-axial apparatus.

Mots clés

  • constitutive equations
  • granular soils
  • deformations
  • instability
  • stability
Accès libre

Comparative Shear Tests of Bolt Rods Under Static and Dynamic Loading

Publié en ligne: 30 Jun 2020
Pages: 151 - 167

Résumé

Abstract

This article presents the methodology and results of single shear tests of bolt rods under dynamic impact loading generated by means of a drop hammer. Comparative analysis was also performed for bolt rod load capacity, stress and shear work under static and dynamic (impact) loading. The developed method of single shear testing of bolt rods under impact loading makes it possible to obtain repeatable test results concerning maximum bolt rod shearing force, shear stress and shear work values.

Comparative shear tests of four types of bolt rods under static and impact loading showed that the APB-type bolt rods made of AP770 steel, which was characterised by having the highest strength, exhibited the greatest shear work. AM22-type bolt rods exhibited a very similar work value. Though the AM22-type bolt rods made of A500sh steel demonstrated lower strength than the APB-type bolts, as well as a smaller diameter and cross section, they dissipated the impact energy better thanks to their higher plasticity. This could indicate the direction of optimisation for bolt rods in order to increase their impact strength.

Mathematical relationships were also formulated for selected tests, describing the real single shear courses F d =f(t) of bolts under impact loading. The obtained relationships could be applied in the load assessment process of bolt rods intended for use under roof caving, tremor and rock burst conditions.

Mots clés

  • rock bolt
  • laboratory bolt test
  • static and dynamic single shear test
  • shear work
Accès libre

Determination of the Atterberg Limits of Eemian Gyttja on Samples with Different Composition

Publié en ligne: 30 Jun 2020
Pages: 168 - 178

Résumé

Abstract

The paper presents the results of laboratory tests of plastic limit wP and liquid limit wL of Eemian gyttja characterized by different organic matter content Iom and calcium carbonate content CaCO3. Comparison of the liquid limit wL determined with the use of the Casagrande apparatus wLC and a cone penetrometer with cones having apex angles of 60° wL60 and 30° wL30 is shown. Based on statistical analysis of the test results, single- and two-factor empirical relationships for evaluating the plastic limit wP and liquid limit wL of Eemian gyttja depending on the organic matter content Iom and/or calcium carbonate content CaCO3 are presented in this study.

Mots clés

  • plastic limit
  • liquid limit
  • Eemian gyttja
  • Casagrande cup
  • cone penetrometer
  • statistical analysis
6 Articles

Research Articles

Accès libre

Modelling the time-dependent behaviour of soft soils

Publié en ligne: 30 Jun 2020
Pages: 97 - 110

Résumé

Abstract

Time dependence of soft soils has already been thoroughly investigated. The knowledge on creep and relaxation phenomena is generally available in the literature. However, it is still rarely applied in practice. Regarding the organic soils, geotechnical engineers mostly base their calculations on the simple assumptions. Yet, as presented within this article, the rate-dependent behaviour of soft soils is a very special and important feature. It influences both the strength and the stiffness of a soil depending on time. It is, thus, significant to account for time dependence in the geotechnical design when considering the soft soils. This can result in a more robust and economic design of geotechnical structures. Hence, the up-to-date possibilities of regarding creep in practice, which are provided by the existing theories, are reviewed herein.

In this article, we first justify the importance of creep effects in practical applications. Next, we present the fundamental theories explaining the time-dependent behaviour of organic soils. Finally, the revision of the existing constitutive models that can be used in numerical simulations involving soft soils is introduced. Both the models that are implemented in the commercial geotechnical software and some more advanced models that take into account further aspects of soft soils behaviour are revised. The assumptions, the basic equations along with the advantages and the drawbacks of the considered models are described.

Mots clés

  • creep
  • soft soil
  • normally consolidated soils
  • elasto-viscoplastic model
Accès libre

An influence of track stiffness discontinuity on pantograph base vibrations and catenary–pantograph dynamic interaction

Publié en ligne: 30 Jun 2020
Pages: 111 - 124

Résumé

Abstract

In this article, the computational methodology of the catenary–train–track system vibration analysis is presented and used to estimate the influence of vehicle body vibrations on the pantograph–catenary dynamic interaction. This issue is rarely referred in the literature, although any perturbations appearing at the pantograph–catenary interface are of great importance for high-speed railways. Vehicle body vibrations considered in this article are induced by the passage of train through the track stiffness discontinuity, being a frequent cause of significant dynamic effects. First, the most important assumptions of the computational model are presented, including the general idea of decomposing catenary–train–track dynamic system into two main subsystems and the concept of one-way coupling between them. Then, the pantograph base vibrations calculated for two train speeds (60 m/s, 100 m/s) and two cases of track discontinuity (a sudden increase and a sudden decrease in the stiffness of track substrate) are analyzed. Two cases of the railway vehicle suspension are considered – a typical two-stage suspension and a primary suspension alone. To evaluate catenary–pantograph dynamic interaction, the dynamic uplift of the contact wire at steady arm and the pantograph contact force is computed. It is demonstrated that an efficiency of the two-stage suspension grows with the train speed; hence, such vehicle suspension effectively suppresses strong sudden shocks of vehicle body, appearing while the train passes through the track stiffness discontinuity at a high speed. In a hypothetical case when the one-stage vehicle suspension is used, the pantograph base vibrations may increase the number of contact loss events at the catenary–pantograph interface.

Mots clés

  • catenary–train–track system
  • track stiffness discontinuity
  • railway vehicle suspension
  • vibration simulations
  • catenary–pantograph dynamic interaction
Accès libre

On determining the undrained bearing capacity coefficients of variation for foundations embedded on spatially variable soil

Publié en ligne: 30 Jun 2020
Pages: 125 - 136

Résumé

Abstract

This paper presents an efficient method and its usage for the three-dimensional random bearing capacity evaluation for square and rectangular footings. One of the objectives of the study is to deliver graphs that can be used to easily estimate the approximated values of coefficients of variations of undrained bearing capacity. The numerical calculations were based on the proposed method that connects three-dimensional failure mechanism, simulated annealing optimization scheme and spatial averaging. The random field is used for describing the spatial variability of undrained shear strength. The proposed approach is in accordance with a constant covariance matrix concept, that results in a highly efficient tool for estimating the probabilistic characteristics of bearing capacity. As a result, numerous three-dimensional simulations were performed to create the graphs. The considered covariance matrix is a result of Vanmarcke’s spatial averaging discretization of a random field in the dissipation regions to the single random variables. The matrix describes mutual correlation between each dissipation region (or between those random variables). However, in the presented approach, the matrix was obtained for the expected value of undrained shear strength and keep constant during Monte Carlo simulations. The graphs were established in dimensionless coordinates that vary in the observable in practice ranges of parameters (i.e., values of fluctuation scales, foundation sizes and shapes). Examples of usage were given in the study to illustrate the application possibility of the graphs. Moreover, the comparison with the approach that uses individually determined covariance matrix is shown.

Mots clés

  • Spatial averaging
  • random fields
  • random bearing capacity
  • fluctuation scale
  • failure mechanism
Accès libre

Deformations and stability of granular soils: Classical triaxial tests and numerical results from an incremental model

Publié en ligne: 30 Jun 2020
Pages: 137 - 150

Résumé

Abstract

This article presents a modified incremental model describing pre-failure deformations of granular soils under classical triaxial conditions. The original shape of equations has been proposed by Sawicki and Świdziński [40, 41]. A new form of equations that are consistent with the proposed definitions of deviatoric loading and unloading is suggested. Triaxial tests necessary for calibrating the proposed model have been performed. The modified model is used to simulate the deformations and stability of sand for every pre-failure loading path and makes it possible to describe the behaviour of granular soil under both drained and undrained conditions.

A comparison of experimental and numerical results is presented. All investigations were performed in a classical tri-axial apparatus.

Mots clés

  • constitutive equations
  • granular soils
  • deformations
  • instability
  • stability
Accès libre

Comparative Shear Tests of Bolt Rods Under Static and Dynamic Loading

Publié en ligne: 30 Jun 2020
Pages: 151 - 167

Résumé

Abstract

This article presents the methodology and results of single shear tests of bolt rods under dynamic impact loading generated by means of a drop hammer. Comparative analysis was also performed for bolt rod load capacity, stress and shear work under static and dynamic (impact) loading. The developed method of single shear testing of bolt rods under impact loading makes it possible to obtain repeatable test results concerning maximum bolt rod shearing force, shear stress and shear work values.

Comparative shear tests of four types of bolt rods under static and impact loading showed that the APB-type bolt rods made of AP770 steel, which was characterised by having the highest strength, exhibited the greatest shear work. AM22-type bolt rods exhibited a very similar work value. Though the AM22-type bolt rods made of A500sh steel demonstrated lower strength than the APB-type bolts, as well as a smaller diameter and cross section, they dissipated the impact energy better thanks to their higher plasticity. This could indicate the direction of optimisation for bolt rods in order to increase their impact strength.

Mathematical relationships were also formulated for selected tests, describing the real single shear courses F d =f(t) of bolts under impact loading. The obtained relationships could be applied in the load assessment process of bolt rods intended for use under roof caving, tremor and rock burst conditions.

Mots clés

  • rock bolt
  • laboratory bolt test
  • static and dynamic single shear test
  • shear work
Accès libre

Determination of the Atterberg Limits of Eemian Gyttja on Samples with Different Composition

Publié en ligne: 30 Jun 2020
Pages: 168 - 178

Résumé

Abstract

The paper presents the results of laboratory tests of plastic limit wP and liquid limit wL of Eemian gyttja characterized by different organic matter content Iom and calcium carbonate content CaCO3. Comparison of the liquid limit wL determined with the use of the Casagrande apparatus wLC and a cone penetrometer with cones having apex angles of 60° wL60 and 30° wL30 is shown. Based on statistical analysis of the test results, single- and two-factor empirical relationships for evaluating the plastic limit wP and liquid limit wL of Eemian gyttja depending on the organic matter content Iom and/or calcium carbonate content CaCO3 are presented in this study.

Mots clés

  • plastic limit
  • liquid limit
  • Eemian gyttja
  • Casagrande cup
  • cone penetrometer
  • statistical analysis

Planifiez votre conférence à distance avec Sciendo