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Detalles de la revista
Formato
Revista
eISSN
2083-831X
Publicado por primera vez
09 Nov 2012
Periodo de publicación
4 veces al año
Idiomas
Inglés

Buscar

Volumen 40 (2018): Edición 4 (December 2018)

Detalles de la revista
Formato
Revista
eISSN
2083-831X
Publicado por primera vez
09 Nov 2012
Periodo de publicación
4 veces al año
Idiomas
Inglés

Buscar

10 Artículos

Research Article

Acceso abierto

Treatment of a collapsible soil using a bentonite–cement mixture

Publicado en línea: 31 Dec 2018
Páginas: 233 - 243

Resumen

Abstract

The study of collapsible soils that are generally encountered in arid and semi-arid regions remains a major issue for geotechnical engineers. This experimental study, carried out on soils reconstituted in the laboratory, aims firstly to present a method of reducing the collapse potential to an acceptable level by treating them with different levels of bentonite–cement mixture while maintaining the water content and degree of compactness, thus reducing eventual risks for the structures implanted on these soils. Furthermore, a microscopic study using scanning electron microscopy was carried out to explore the microstructure of the soil in order to have an idea of the phenomena before and after treatment. The results show that treatment with a bentonite–cement mixture improves the geotechnical and mechanical characteristics, modifies the chemical composition of the soil, reduces the collapse potential and the consistency limits. The microstructural study and the X-ray energy dispersive spectroscopy analysis clearly illustrate an association of elementary particles in the soil aggregates, whereby the arrangement of these aggregates leads to the formation of a dense and stable material.

Palabras clave

  • collapsible soil
  • cement
  • bentonite
  • microstructure
  • oedometer
Acceso abierto

Effectiveness of reinforcing an earth structure with a system of counterfort drains over a long-term use

Publicado en línea: 04 Jan 2019
Páginas: 244 - 253

Resumen

Abstract

The paper evaluates the effectiveness of reinforcing a damaged earth structure with making counterfort drains in its slope. The system of counterfort drains changed the soil properties significantly over a long-term use. The evaluation was based on many years of field and laboratory tests and stability analysis. The field tests concerned the observation of N WST probing resistance change, and the laboratory tests concerned the change in soil consistency and water content. The paper presents the results of tests that were conducted over 13 years.

Palabras clave

  • counterfort drain
  • landslide
  • geotechnical monitoring
  • slope stability analysis
  • weight sounding test (WST)
  • soil laboratory tests
Acceso abierto

Experimental determination of the kinetics of sorption and gas filtration in coal

Publicado en línea: 26 Sep 2018
Páginas: 254 - 262

Resumen

Abstract

The paper presents tests set-ups for experiments on sorption kinetics and gas filtration kinetics in a porous medium. It was observed that two phenomena occur in these processes: transportation of gas into the porous solid and settling of gas molecules on the walls of the solid or within its volume. An experiment was carried out in which a thin resistance thermometer was quickly taken out of an argon stream and placed in carbon dioxide or the other way round. The measurement made it possible to determine the sorption time constant. It was demonstrated that the sorption rate is much higher than the filtration rate. Thus, filtration is the process describing the rate at which gas molecules penetrating the porous substance are adsorbed or desorbed. The sorption time constant is not >50 m.

In the second experiment, the author determined the rate at which gas is liberated from coal grains. The measurement method was based on measurement of the pressure of desorbing gas in constant volume. The experiment involved measurement of the pressure of the gas liberated from the coal grains in a closed chamber. The kinetic curves obtained in this way were used to determine the carbon dioxide coefficient in coal grains. During the experiment, particular focus was put on the initial stage of gas liberation (up to 0.4 s).

The slower process of gas transporting in the porous structure of coal is the transporting of gas through a coal briquette. Experimentally implemented variety of boundary conditions allowed for a more complete verification of the assumed theoretical model and possibly for the exact determination of filtration parameters. The experimental set-up built for this purpose, allows for pressure and temperature measurement on the briquette side surface.

Palabras clave

  • sorption
  • filtration
  • sorption kinetics
  • filtration kinetics
Acceso abierto

A system consists of lifted steel tank and four assembly supports with variable assembly conditions

Publicado en línea: 27 Nov 2018
Páginas: 263 - 269

Resumen

Abstract

In the method of steel tank erection, consisting in assembling the roof and the next courses (segments) of the shell at the ground level, starting from the top one (the so-called hydraulic jacking-up method), the assembled part of the tank is lifted using assembly supports (towers, trestles), hydraulic jacks and ropes. Supports are located inside or outside the tank, and their bases are usually not anchored. During the assembly work, numerous contaminations can appear under the bases of the supports; therefore, boundary conditions of the system consisting of the elevated tank and assembly supports may change, influencing the field of displacements and stresses in the elements of this system. This article presents the results of numerical tests of an exemplary mounted tank – mounting support system – at various possible coefficients of friction between the bases of the supports and the ground. The influence of the support conditions on the effort of the essential elements of the system was assessed. Calculation difficulty was noted to determine the directions of horizontal responses of the supports. It was assumed that these directions did not change after exceeding the values of the friction forces. The analysed tank collapsed during its erection.

Palabras clave

  • Tank
  • method of erection
  • hydraulic jacking
  • disaster
Acceso abierto

Numerical solution through mathematical modelling of unsteady MHD flow past a semi-infinite vertical moving plate with chemical reaction and radiation

Publicado en línea: 31 Dec 2018
Páginas: 270 - 281

Resumen

Abstract

In the present manuscript, unsteady magnetohydrodynamic (MHD) flow over a moving porous semi-infinite vertical plate with time-dependent suction has been studied in the presence of chemical reaction and radiation parameters. Time-dependent partial differential equations in the dimensionless form are solved numerically through mathematical modelling in COMSOL Multiphysics. The results are obtained for velocity, temperature and concentration profiles at different times. Steady state results are also presented for different values of physical parameters. The parameters involved in the problem are useful to change the characteristics of velocity, heat transfer and concentration profiles. The numerical solution of partial differential equations involved in the problem is obtained without sacrificing the relevant physical phenomena.

Palabras clave

  • MHD flow
  • chemical reaction
  • radiation
  • numerical solution
Acceso abierto

Stress states caused in chamber of reinforced concrete grain silo by non-centric emptying on large eccentricities

Publicado en línea: 31 Dec 2018
Páginas: 282 - 291

Resumen

Abstract

The article presents the analysis of complex stress states in the concrete structure of grain silos, caused by non-centric emptying. The authors present a combination of loads from the pressure of bulk solid on the silo chamber according to Eurocode 1, Part 4 [11], which should be taken into account when emptying on large eccentricities in action assessment class 3 (AAC3) silos. For the example of a cylindrical wheat silo with a height of 25 m and a diameter of 10 m, the researchers carried out an analysis regarding the impact of the size of the eccentric discharge outlet on the distributions of forces and bending moments in a reinforced concrete wall.

Palabras clave

  • stress states
  • reinforced concrete structure
  • grain silo
  • non-centric emptying
Acceso abierto

Low-Strength Substrates and Anthropogenic Soils in Transportation Engineering

Publicado en línea: 26 Dec 2018
Páginas: 292 - 299

Resumen

Abstract

Road embankments, especially their slopes’ surfaces, must fulfil all the requirements concerning the exploitation criteria after the completion of construction works. This is very important while constructing or modernizing the embankments, based on the substrate including low-strength soils as well as in simple ground conditions (most convenient). The last dozen or so years of intensive construction of transport infrastructure have shown how big is the problem of ensuring the required volumes of qualified soil material for the construction of road embankments or the modernization of railway embankments. The depleting deposits of natural and easily accessible soils for the construction of embankments result in the need to use anthropogenic soils, for example, in the form of aggregates from the recycling of construction waste and other locally available waste materials, usually in the form of slag and ashes from the combined heat and power plants. In such cases, there’s a need to treat transportation earth structures individually in the scope of designing and quality control, because there are no applicable standard provisions in this scope.

This work indicates some of these important contemporary problems of transport engineering, occurring in newly built and modernized road objects, such as the stability of road embankments based on a low-strength substrate, use of anthropogenic soils and materials originating from the recycling of concrete surfaces for the construction of road embankments.

Palabras clave

  • Transport engineering
  • road embankments
  • soft soils
  • anthropogenic soils
Acceso abierto

Stability of Road Earth Structures in the Complex And Complicated Ground Conditions

Publicado en línea: 26 Sep 2018
Páginas: 300 - 312

Resumen

Abstract

Some important modern problems of the transport engineering, which occur in the newly built and modernised road objects, have been indicated in the work. A discussion was conducted regarding the methods of assessing the stability of slopes of the road embankments, the obtained stability margins and the interpretation of obtained results in the specific cases of foundations of the road earth structures. Presented observations result from analysing the stability assessments of slopes of the road embankments, which was conducted on many communication objects, characterised by high variability of foundation conditions.

Palabras clave

  • slope stability
  • road embankments
  • transport engineering
  • soft soils
Acceso abierto

Influence of bedding and backfill soil type on deformation of buried sewage pipeline

Publicado en línea: 21 Dec 2018
Páginas: 313 - 320

Resumen

Abstract

In the paper, the influence of different types of bedding and backfill soil surrounding underground sewage duct on its deformation was analysed. Impact of increased soil lateral pressure was examined by considering the construction of an embankment nearby the underground pipeline. Numerical computations of three different variants of bedding and backfill soil surrounding the pipe were carried out. Displacements and deformation of the pipe were calculated using the finite element method with adoption of elastic-perfectly plastic constitutive model of soil. Subsequent stages of the construction were taken into account. Shear strength reduction method was applied to evaluate the factor of safety of the entire system. Finally, the results and conclusions were depicted.

Palabras clave

  • Numerical analysis
  • buried PE pipe
Acceso abierto

Experimental identification of modal parameters for the model of a building subjected to short-term kinematic excitation

Publicado en línea: 31 Dec 2018
Páginas: 321 - 332

Resumen

Abstract

In this work, the input-output method of dynamic parameters' identification is experimentally tested. A method based on the transformation of a dynamic problem into a static problem by means of integration of the input and output signal was presented. The problem discussed in this article is the identification of the coefficients of stiffness matrices and eigenfrequencies of a discrete dynamic system subjected to kinematic input. The experimental analysis was carried out on a three-storey slab-and-column structure, which constitutes a physical model of a building. The vibrations of the model were excited kinematically by an earthquake simulator. The device has a computer-controlled, movable table top, which can move independently in three directions, that is, horizontally, vertically, and rotationally around the vertical axis.

The aim of the experimental studies presented in this work was to determine the dynamic parameters of the model (stiffness, natural frequencies) using the input-output method in the time domain. Moreover, the results obtained with this method were compared with the results of experimental modal analysis (EMA) in order to verify their correctness. It was assumed that the movement of the base is horizontal and occurs in one direction. Two short-term, irregular kinematic excitations of the construction were considered, and the selected results and conclusions from experimental analyses were presented in this work.

Palabras clave

  • experimental studies
  • input-output method
  • identification of modal parameters
  • kinematic excitation
10 Artículos

Research Article

Acceso abierto

Treatment of a collapsible soil using a bentonite–cement mixture

Publicado en línea: 31 Dec 2018
Páginas: 233 - 243

Resumen

Abstract

The study of collapsible soils that are generally encountered in arid and semi-arid regions remains a major issue for geotechnical engineers. This experimental study, carried out on soils reconstituted in the laboratory, aims firstly to present a method of reducing the collapse potential to an acceptable level by treating them with different levels of bentonite–cement mixture while maintaining the water content and degree of compactness, thus reducing eventual risks for the structures implanted on these soils. Furthermore, a microscopic study using scanning electron microscopy was carried out to explore the microstructure of the soil in order to have an idea of the phenomena before and after treatment. The results show that treatment with a bentonite–cement mixture improves the geotechnical and mechanical characteristics, modifies the chemical composition of the soil, reduces the collapse potential and the consistency limits. The microstructural study and the X-ray energy dispersive spectroscopy analysis clearly illustrate an association of elementary particles in the soil aggregates, whereby the arrangement of these aggregates leads to the formation of a dense and stable material.

Palabras clave

  • collapsible soil
  • cement
  • bentonite
  • microstructure
  • oedometer
Acceso abierto

Effectiveness of reinforcing an earth structure with a system of counterfort drains over a long-term use

Publicado en línea: 04 Jan 2019
Páginas: 244 - 253

Resumen

Abstract

The paper evaluates the effectiveness of reinforcing a damaged earth structure with making counterfort drains in its slope. The system of counterfort drains changed the soil properties significantly over a long-term use. The evaluation was based on many years of field and laboratory tests and stability analysis. The field tests concerned the observation of N WST probing resistance change, and the laboratory tests concerned the change in soil consistency and water content. The paper presents the results of tests that were conducted over 13 years.

Palabras clave

  • counterfort drain
  • landslide
  • geotechnical monitoring
  • slope stability analysis
  • weight sounding test (WST)
  • soil laboratory tests
Acceso abierto

Experimental determination of the kinetics of sorption and gas filtration in coal

Publicado en línea: 26 Sep 2018
Páginas: 254 - 262

Resumen

Abstract

The paper presents tests set-ups for experiments on sorption kinetics and gas filtration kinetics in a porous medium. It was observed that two phenomena occur in these processes: transportation of gas into the porous solid and settling of gas molecules on the walls of the solid or within its volume. An experiment was carried out in which a thin resistance thermometer was quickly taken out of an argon stream and placed in carbon dioxide or the other way round. The measurement made it possible to determine the sorption time constant. It was demonstrated that the sorption rate is much higher than the filtration rate. Thus, filtration is the process describing the rate at which gas molecules penetrating the porous substance are adsorbed or desorbed. The sorption time constant is not >50 m.

In the second experiment, the author determined the rate at which gas is liberated from coal grains. The measurement method was based on measurement of the pressure of desorbing gas in constant volume. The experiment involved measurement of the pressure of the gas liberated from the coal grains in a closed chamber. The kinetic curves obtained in this way were used to determine the carbon dioxide coefficient in coal grains. During the experiment, particular focus was put on the initial stage of gas liberation (up to 0.4 s).

The slower process of gas transporting in the porous structure of coal is the transporting of gas through a coal briquette. Experimentally implemented variety of boundary conditions allowed for a more complete verification of the assumed theoretical model and possibly for the exact determination of filtration parameters. The experimental set-up built for this purpose, allows for pressure and temperature measurement on the briquette side surface.

Palabras clave

  • sorption
  • filtration
  • sorption kinetics
  • filtration kinetics
Acceso abierto

A system consists of lifted steel tank and four assembly supports with variable assembly conditions

Publicado en línea: 27 Nov 2018
Páginas: 263 - 269

Resumen

Abstract

In the method of steel tank erection, consisting in assembling the roof and the next courses (segments) of the shell at the ground level, starting from the top one (the so-called hydraulic jacking-up method), the assembled part of the tank is lifted using assembly supports (towers, trestles), hydraulic jacks and ropes. Supports are located inside or outside the tank, and their bases are usually not anchored. During the assembly work, numerous contaminations can appear under the bases of the supports; therefore, boundary conditions of the system consisting of the elevated tank and assembly supports may change, influencing the field of displacements and stresses in the elements of this system. This article presents the results of numerical tests of an exemplary mounted tank – mounting support system – at various possible coefficients of friction between the bases of the supports and the ground. The influence of the support conditions on the effort of the essential elements of the system was assessed. Calculation difficulty was noted to determine the directions of horizontal responses of the supports. It was assumed that these directions did not change after exceeding the values of the friction forces. The analysed tank collapsed during its erection.

Palabras clave

  • Tank
  • method of erection
  • hydraulic jacking
  • disaster
Acceso abierto

Numerical solution through mathematical modelling of unsteady MHD flow past a semi-infinite vertical moving plate with chemical reaction and radiation

Publicado en línea: 31 Dec 2018
Páginas: 270 - 281

Resumen

Abstract

In the present manuscript, unsteady magnetohydrodynamic (MHD) flow over a moving porous semi-infinite vertical plate with time-dependent suction has been studied in the presence of chemical reaction and radiation parameters. Time-dependent partial differential equations in the dimensionless form are solved numerically through mathematical modelling in COMSOL Multiphysics. The results are obtained for velocity, temperature and concentration profiles at different times. Steady state results are also presented for different values of physical parameters. The parameters involved in the problem are useful to change the characteristics of velocity, heat transfer and concentration profiles. The numerical solution of partial differential equations involved in the problem is obtained without sacrificing the relevant physical phenomena.

Palabras clave

  • MHD flow
  • chemical reaction
  • radiation
  • numerical solution
Acceso abierto

Stress states caused in chamber of reinforced concrete grain silo by non-centric emptying on large eccentricities

Publicado en línea: 31 Dec 2018
Páginas: 282 - 291

Resumen

Abstract

The article presents the analysis of complex stress states in the concrete structure of grain silos, caused by non-centric emptying. The authors present a combination of loads from the pressure of bulk solid on the silo chamber according to Eurocode 1, Part 4 [11], which should be taken into account when emptying on large eccentricities in action assessment class 3 (AAC3) silos. For the example of a cylindrical wheat silo with a height of 25 m and a diameter of 10 m, the researchers carried out an analysis regarding the impact of the size of the eccentric discharge outlet on the distributions of forces and bending moments in a reinforced concrete wall.

Palabras clave

  • stress states
  • reinforced concrete structure
  • grain silo
  • non-centric emptying
Acceso abierto

Low-Strength Substrates and Anthropogenic Soils in Transportation Engineering

Publicado en línea: 26 Dec 2018
Páginas: 292 - 299

Resumen

Abstract

Road embankments, especially their slopes’ surfaces, must fulfil all the requirements concerning the exploitation criteria after the completion of construction works. This is very important while constructing or modernizing the embankments, based on the substrate including low-strength soils as well as in simple ground conditions (most convenient). The last dozen or so years of intensive construction of transport infrastructure have shown how big is the problem of ensuring the required volumes of qualified soil material for the construction of road embankments or the modernization of railway embankments. The depleting deposits of natural and easily accessible soils for the construction of embankments result in the need to use anthropogenic soils, for example, in the form of aggregates from the recycling of construction waste and other locally available waste materials, usually in the form of slag and ashes from the combined heat and power plants. In such cases, there’s a need to treat transportation earth structures individually in the scope of designing and quality control, because there are no applicable standard provisions in this scope.

This work indicates some of these important contemporary problems of transport engineering, occurring in newly built and modernized road objects, such as the stability of road embankments based on a low-strength substrate, use of anthropogenic soils and materials originating from the recycling of concrete surfaces for the construction of road embankments.

Palabras clave

  • Transport engineering
  • road embankments
  • soft soils
  • anthropogenic soils
Acceso abierto

Stability of Road Earth Structures in the Complex And Complicated Ground Conditions

Publicado en línea: 26 Sep 2018
Páginas: 300 - 312

Resumen

Abstract

Some important modern problems of the transport engineering, which occur in the newly built and modernised road objects, have been indicated in the work. A discussion was conducted regarding the methods of assessing the stability of slopes of the road embankments, the obtained stability margins and the interpretation of obtained results in the specific cases of foundations of the road earth structures. Presented observations result from analysing the stability assessments of slopes of the road embankments, which was conducted on many communication objects, characterised by high variability of foundation conditions.

Palabras clave

  • slope stability
  • road embankments
  • transport engineering
  • soft soils
Acceso abierto

Influence of bedding and backfill soil type on deformation of buried sewage pipeline

Publicado en línea: 21 Dec 2018
Páginas: 313 - 320

Resumen

Abstract

In the paper, the influence of different types of bedding and backfill soil surrounding underground sewage duct on its deformation was analysed. Impact of increased soil lateral pressure was examined by considering the construction of an embankment nearby the underground pipeline. Numerical computations of three different variants of bedding and backfill soil surrounding the pipe were carried out. Displacements and deformation of the pipe were calculated using the finite element method with adoption of elastic-perfectly plastic constitutive model of soil. Subsequent stages of the construction were taken into account. Shear strength reduction method was applied to evaluate the factor of safety of the entire system. Finally, the results and conclusions were depicted.

Palabras clave

  • Numerical analysis
  • buried PE pipe
Acceso abierto

Experimental identification of modal parameters for the model of a building subjected to short-term kinematic excitation

Publicado en línea: 31 Dec 2018
Páginas: 321 - 332

Resumen

Abstract

In this work, the input-output method of dynamic parameters' identification is experimentally tested. A method based on the transformation of a dynamic problem into a static problem by means of integration of the input and output signal was presented. The problem discussed in this article is the identification of the coefficients of stiffness matrices and eigenfrequencies of a discrete dynamic system subjected to kinematic input. The experimental analysis was carried out on a three-storey slab-and-column structure, which constitutes a physical model of a building. The vibrations of the model were excited kinematically by an earthquake simulator. The device has a computer-controlled, movable table top, which can move independently in three directions, that is, horizontally, vertically, and rotationally around the vertical axis.

The aim of the experimental studies presented in this work was to determine the dynamic parameters of the model (stiffness, natural frequencies) using the input-output method in the time domain. Moreover, the results obtained with this method were compared with the results of experimental modal analysis (EMA) in order to verify their correctness. It was assumed that the movement of the base is horizontal and occurs in one direction. Two short-term, irregular kinematic excitations of the construction were considered, and the selected results and conclusions from experimental analyses were presented in this work.

Palabras clave

  • experimental studies
  • input-output method
  • identification of modal parameters
  • kinematic excitation

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