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On the application of a mixed finite-element approach to beam-soil interaction
Vedran Jagodnik, Gordan Jelenić, Željko Arbanas, 2013, izvirni znanstveni članek

Opis: In this paper the deformation of a Bernoulli beam resting on Winkler's soil is reviewed in terms of the mixed finite-element methodology. While the stiffness matrix of the Bernoulli beam problem utilizing the standard displacement-based approach, in which only the displacement field is interpolated, may be alternatively obtained using a mixed-type approach to the absolutely shear-stiff second-order Timoshenko beam (in which the rotation and shear-stress resultant fields are additionally interpolated), the two approaches lead to different Winkler-type soil-stiffness contributions. Furthermore, extending the mixed-type formalism to both of these elements by additionally interpolating the distributed soil-reaction field, the soil-stiffness contributions also differ. In this way four different elements are obtained, with one, two, three or four independently interpolated fields, in which the beam-stifness matrix is equal, but the soil-stiffness matrices are different. It is demonstrated that the displacement-based one-field element is the least convergent, while the mixed-type element with four interpolated fields is the most convergent.
Ključne besede: Bernoulli beam, Winkler soil, mixed finite-element method
Objavljeno: 14.06.2018; Ogledov: 30; Prenosov: 5
.pdf Celotno besedilo (413,70 KB)

Atterberg limits in relation to other properties of fine-grained soils
Bojana Dolinar, Stanislav Škrabl, 2013, izvirni znanstveni članek

Opis: In soil mechanics the Atterberg limits are the most distinctive and the easiest property of fine-grained soils to measure. As they depend on the same physical factors as the other mechanical properties of soils, the values of the liquid and plastic limits would be a very convenient basis for their prediction. There are many studies concerning the use of the Atterberg limits in soil mechanics; however, their results vary considerably and are not generally applicable. This paper explains the main reasons for the different conclusions in these studies, which do not take into account the following: a) the water in fine-grained soils appears as interparticle and interaggregate pore water as well as adsorbed water onto the surfaces of clay minerals; b) the physical properties of fine-grained soils depend on the quantity of pore water only, because the adsorbed water is tightly tied on the clayʼs external and internal surfaces and thus cannot influence to them; c) the quantity of adsorbed water on the external surfaces of the clay minerals in soils depends mostly on the size and the quantity of the clay minerals, while the interlayer water quantity depends mostly on the quantity and the type of the swelling clay minerals in the soil composition and their exchangeable cations. From this it follows that for swelling and non-swelling soils, the uniform relationships between the Atterberg limits (which represent the total quantity of pore water and the adsorbed water onto the external and internal surfaces of clay minerals) and other physical properties does not exist. This paper presents some possibilities for the use of the Atterberg limits in predicting the soilʼs other properties for non-swelling and limited-swelling soils.
Ključne besede: Atterberg limits, specific surface area, undrained shear strength, compressibility, hydraulic conductivity
Objavljeno: 14.06.2018; Ogledov: 28; Prenosov: 7
.pdf Celotno besedilo (133,59 KB)

Ludvik Trauner, 2013, predgovor, spremna beseda

Ključne besede: editorials, scientific journals, geomechanics, geotechnical engineering
Objavljeno: 14.06.2018; Ogledov: 30; Prenosov: 6
.pdf Celotno besedilo (37,30 KB)
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Experimental and numerical studies of T-shaped footings
Nihat Kaya, Murat Ornek, 2013, izvirni znanstveni članek

Opis: In addition to vertical axial loads, the footings of structures are often subjected to eccentric loads caused by the forces of earth pressures, earthquakes, water, wind, etc. Due to eccentric loading, the two edges settle by different amounts, causing the footing to tilt and then the pressure below the footing does not remain uniform. The T-shape is proposed as a footing shape for improving the bearing capacity of shallow footings against the action of eccentric loads. The vertical insertion of the rigid T-shaped footing, into the bearing soil, provides considerable resistance, against both of sliding and overturning, enough to regain the reduction in bearing capacity and increase in settlement. In this study, a series of experimental and numerical results from the ultimate loads and settlement of T-shaped footings are reported. A total of 48 model tests were conducted for investigating the effects of different parameters, such as the problem geometry and soil density. The problem geometry was represented by two parameters, the load eccentricity (e) and the insertion depth (H) of the T-shape into the loose and dense sand soil. After the experimental stage, the numerical analyses were carried out using a plane strain, two-dimensional, finite-element-based computer program. The behaviour of the T-shape footing on sand beds is represented by the hardening soil model. The results of the experimental and numerical studies proved that the ultimate bearing capacity of a footing under eccentric loads could be improved by inserting a vertical central cut-off rigidly connected to the footing bottom. The load settlement curves indicate that the higher load eccentricity results in a decrease in the bearing capacity of the strip footing. It was also proved that the ultimate bearing capacity values can, depending on the soil density, be improved by up to four times that of the loose sand case. This investigation is considered to have provided a useful basis for further research, leading to an increased understanding of the T-shaped footing design.
Ključne besede: model test, finite-element method, T-shaped footing, eccentric loading, sand
Objavljeno: 14.06.2018; Ogledov: 49; Prenosov: 4
.pdf Celotno besedilo (686,03 KB)

Post-liquefaction volume change in micaceous sandy of Old Gediz River Delta
Ender Basari, Gurkan Ozden, 2013, izvirni znanstveni članek

Opis: Post-liquefaction settlement characteristics of micaceous sands are not well investigated topic. Currently available charts relating post-liquefaction volumetric strain to relative density were developed for clean sand. Estimation of post-liquefaction settlement of micaceous sands, therefore, may stay on the unsafe side, since there is evidence indicating that mica grains could increase volume change tendency. Influence of mica content on post-liquefaction volumetric strain of sand-mica mixtures is studied in this article. Soil samples were prepared at various relative densities. Influence of fine content that could be present in the field was also investigated on tamped natural field samples recovered from boreholes drilled in a highly populated alluvial site known as the Old Gediz River Delta of Izmir. It was found that increasing mica content at a certain relative density resulted in higher volumetric strains as compared with the data on clean sands. It is deduced that influence of mica grains on sand behavior depends on initial void ratio of sand. Effects of mica grains decrease with increasing of relative density. Simple empirical relationships were derived relating mica content and relative density to volumetric strain. It was also noticed that fine content accelerated and increased post-liquefaction volumetric strains.
Ključne besede: sand, mica, non-plastic fines, post-liquefaction volume change
Objavljeno: 14.06.2018; Ogledov: 50; Prenosov: 18
.pdf Celotno besedilo (434,60 KB)

An estimation of the passive pressure against integral bridge abutments considering arching effects
Mojtaba Movahedifar, Jafar Bolouri Bazaz, 2013, izvirni znanstveni članek

Opis: Most civil engineering structures are subjected to cyclic loading during their service life, such as retaining walls, wave loading on offshore structures, seismic loading and the traffic loading of pavements. In the case of an integral abutment bridge (IAB), as an example, the backfill granular material is subject to slow cyclic stress and strain changes under drained conditions. These bridges are constructed so that the top deck is longitudinally continuous. In other words, IABs are joint-less bridges where the superstructure is connected with the abutment. The rigid connection enables the abutment and superstructure to act as a single structural unit, i.e., the expansion joints which are widely used in traditional bridges are removed in IABs. This removal is mainly due to the high costs of maintenance. The behavior of IABs is dominated by the cyclical temperature changes in the bridge deck. This results in the imposition of cyclical horizontal displacements to the backfill soil of the abutments. The present research is an effort to investigate the induced passive pressure on the IABs, using a laboratory model and an analytical approach. The results indicate that the passive pressure distribution is non-linear and its maximum value along the wall is dependent on the magnitude of the wall rotation and number of cycles. It seems that there are two different mechanisms for this behavior. In the above part of the wall, sand behaves as a plastic material. A decline in the passive pressure in the bottom part, however, is the result of arching.
Ključne besede: integral abutment bridge, cyclic displacement, passive pressure, arching
Objavljeno: 14.06.2018; Ogledov: 38; Prenosov: 11
.pdf Celotno besedilo (609,10 KB)

The importance of tensile strength in geotechnical engineering
Ivan Vaníček, 2013, izvirni znanstveni članek

Opis: Many Soil mechanics textbooks contain only limited information about tensile characteristics. Šuklje’s “Rheological aspects of soil mechanics” [1] is an exception, as he devoted a special chapter to this problem “Tensile and Bending Strength of Soils”. Therefore, it is not a great surprise that the subject of the 13th Šuklje’s Lecture is devoted to soil behaviour in tension. Tensile tests are briefly described, some results as well, with a distinction between undrained and drained tests. Practical examples of the application of the results are discussed, firstly in cases where the development of tensile cracks can be expected. Because the results of the drained tests give more information about the bonds between individual particles, some theoretical aspects of these tests are discussed as well.
Ključne besede: tensile cracks, tensile strength, bending, triaxial drained tensile test
Objavljeno: 14.06.2018; Ogledov: 27; Prenosov: 8
.pdf Celotno besedilo (549,04 KB)

Ludvik Trauner, 2013, predgovor, spremna beseda

Ključne besede: editorials, scientific journals, geomechanics, geotechnical engineering
Objavljeno: 14.06.2018; Ogledov: 28; Prenosov: 27
.pdf Celotno besedilo (35,77 KB)
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Zeolitization characteristics of fly ashes from wet- and dry- disposal systems
Bhagwanjee Jha, D. N. Singh, 2012, izvirni znanstveni članek

Opis: The fly ash disposal at thermal power plants is either through wet- or dry-disposal systems. As these disposal practices result in different characteristics for the fly ashes, their interaction with alkalis, and hence the zeolitization potential, will be different. In order to demonstrate this, investigations were conducted to study the physical, chemical, mineralogical and morphological characteristics of the residues of the fly ashes collected from the lagoons and hoppers of the same thermal power plant, after their hydrothermal treatment. Field-emission-gun scanning electron microscopy and X-ray diffraction analysis of these residues demonstrated that the hopper ash attains an exceptionally high cation-exchange capacity and $SiO_2/Al_2O_3$ ratios (SAR), which correspond to the formation of major fly ash zeolites as compared to its counterpart. In other words, the study presented here helps to establish the superiority of hopper ash over lagoon ash for synthesizing fly ash zeolites and their enhanced quantity and quality.
Ključne besede: alkali activation, lagoon ash, hopper ash, fly ash zeolites
Objavljeno: 13.06.2018; Ogledov: 109; Prenosov: 22
.pdf Celotno besedilo (227,88 KB)

Probabilistic study of the phenomenon of crushed grains using the model of Weibull
Kheffache Toufik, Melbouci Bachir, 2012, izvirni znanstveni članek

Opis: The crushing of grains in a granular medium is a very important phenomenon; it is a source of both physical and mechanical changes to these materials. A statistical study of the mechanical properties of a material was used to characterize the distribution and fracture mechanics in order to quantify the evolution of these distributions with sample sizes (grains and whole grains). This work presents the results of an experimental study made on the crushing of individual grains of limestone and samples consisting of multiple grains subjected to a uniaxial loading in order to highlight the influence of the loading and the grain size on the rate of crushing. A statistical study using the Weibull method allowed us to model the problem and quantify the rate of breakage for the two cases. The results obtained show that the rate of deflection depends on the grain size and the intensity of the applied load. Statistical modelling using the Weibull method gave us acceptable results in both cases.
Ključne besede: grain, sample, crushing, statistical study
Objavljeno: 13.06.2018; Ogledov: 86; Prenosov: 6
.pdf Celotno besedilo (335,52 KB)

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