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81.
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: 10; Prenosov: 0
.pdf Celotno besedilo (434,60 KB)

82.
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: 7; Prenosov: 1
.pdf Celotno besedilo (609,10 KB)

83.
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: 8; Prenosov: 1
.pdf Celotno besedilo (549,04 KB)

84.
Editorial
Ludvik Trauner, 2013, predgovor, spremna beseda

Ključne besede: editorials, scientific journals, geomechanics, geotechnical engineering
Objavljeno: 14.06.2018; Ogledov: 5; Prenosov: 0
.pdf Celotno besedilo (35,77 KB)
Gradivo ima več datotek! Več...

85.
Metode za dimenzioniranje krožnih križišč
Mitja Zrim, 2018, magistrsko delo/naloga

Opis: V magistrskem delu smo v začetku podali splošne informacije o krožnih križiščih. Temu je sledila razlaga pojma projektiranje in dimenzioniranje krožnih križišč s prikazom procesa dimenzioniranja v primeru, ko iščemo najprimernejšo rešitev. Navedli smo v katere glavne skupine delimo metode za dimenzioniranje in katere so posebnosti teh skupin. Metod za dimenzioniranje krožnih križišč je dandanes že veliko, zato smo se omejili na avstrijsko, avstralsko, angleško, francosko, nemško, HCM 2016 in HBS 2015 metodo. Podali smo splošen opis teh metod in prikazali postopek izvedbe analize pri posamezni metodi. S pomočjo teoretičnih dejstev smo izvedli teoretično primerjavo metod v smislu, katere vhodne podatke zahteva posamezna metoda, katere rezultate dobimo pri posamezni metodi in podali subjektivno oceno metod. Primerjali smo tudi rezultate izračuna prepustnosti po enačbah vseh prej omenjenih metod za primer enopasovnega krožnega križišča in jih prikazali v grafičnem zapisu. Pri tem smo spoznali, da pri nekaterih metodah prihaja do precejšnjega odstopanja. Metode smo uporabili tudi na dejanskem primeru enopasovnega krožnega križišča, ki se nahaja v Mestni občini Murska Sobota in s pomočjo dobljenih rezultatov izvedli primerjavo z navedbo razlage, zakaj prihaja do razlik v rezultatih, kaj na to vpliva ter navedli priporočila za dimenzioniranje.
Ključne besede: gradbeništvo, krožna križišča, metode za dimenzioniranje, prepustnost
Objavljeno: 13.06.2018; Ogledov: 64; Prenosov: 16
.pdf Celotno besedilo (4,32 MB)

86.
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: 51; Prenosov: 1
.pdf Celotno besedilo (227,88 KB)

87.
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: 48; Prenosov: 1
.pdf Celotno besedilo (335,52 KB)

88.
A new solution for shallow and deep tunnels by considering the gravitational loads
Mohammad Reza Zareifard, Ahmad Fahimifar, 2012, izvirni znanstveni članek

Opis: A new, elasto-plastic, analytical-numerical solution, considering the axial-symmetry condition, for a circular tunnel excavated in a strain-softening and Hoek–Brown rock mass is proposed. To examine the effect of initial stress variations, and also the boundary conditions at the ground surface, the formulations are derived for different directions around the tunnel. Furthermore, the effect of the weight of the plastic zone is taken into account in this regard. As the derived differential equations have no explicit analytical solutions for the plastic zone, the finite-difference method (FDM) is used in this study. On the other hand, analytical expressions are derived for the elastic zone. Several illustrative examples are given to demonstrate the performance of the proposed solution, and to examine the effect of various boundary conditions. It is concluded that the classic solutions, based on the hydrostatic far-field stress, and neglecting the effect of the boundary conditions at the ground surface, give applicable results for a wide range of practical problems. However, ignoring the weight of the plastic zone in the analyses can lead to large errors in the calculations.
Ključne besede: ground-response curve, elasto-plastic analysis, boundary condition, axial symmetry, gravitational loads
Objavljeno: 13.06.2018; Ogledov: 51; Prenosov: 0
.pdf Celotno besedilo (406,96 KB)

89.
Numerical modeling of floating prefabricated vertical drains in layered soil
Ikhya Ikhya, Helmut Schweiger, 2012, izvirni znanstveni članek

Opis: This paper presents a comparison of field measurements and a numerical model of settlements based on the construction of an embankment on soft soil for the Cirebon Power Plant Project in Indonesia, where prefabricated vertical drains (PVDs) were installed. In the numerical model, floating PVDs in two soil layers for two- and one-way drainage conditions are examined in order to determine the optimum penetration depth. In this study, good agreement between the field measurements of the settlements and the numerical prediction could be achieved. An interesting result of this study is that the differences in the stiffness and/or the permeability in the unimproved area below the PVD tip have a significant influence on the optimum penetration depth (L/H) in the two-soil-layer condition. The numerical study showed that it is possible to use floating PVDs in single drainage conditions if the second layer is stiffer and/or more permeable than the first layer.
Ključne besede: two soil layers, floating prefabricated vertical drain, double and single drainage, numerical model, soft clay, consolidation
Objavljeno: 13.06.2018; Ogledov: 42; Prenosov: 0
.pdf Celotno besedilo (727,36 KB)

90.
A comparison between conventional triaxial and plane-strain compression on a particulate system using 3D DEM
Mahmud Sazzad, Kiichi Suzuki, 2012, izvirni znanstveni članek

Opis: Granular materials such as sand are subjected to different stress paths depending on the in-situ conditions. For example, a granular system under the foundations experiences conventional triaxial compression (CTC), while it experiences plane-strain compression (PSC) in the case of the embankment of roads. Due to the difference in the stress paths, the behavior of granular materials also becomes different. This paper aims at comparing the behavior of granular materials under CTC and PSC conditions using the 3D discrete-element method (DEM). An isotropically compressed dense sample consisting of 8000 spheres was prepared numerically using periodic boundaries. The CTC and PSC tests were simulated using the same isotropically compressed dense sample to compare and explore the macro- and micro-mechanical responses of granular materials without any bias from the initial fabric of the numerical sample. Qualitatively, the simulated stress-strain responses are consistent with that observed in the experimental studies. The dilatancy index is found to be independent of the stress paths used in the present study. The b value (defined as b = (σ2 − σ3)/(σ1 − σ3) where σ1, σ2 and σ3 are the stresses in the x1 -, x2 - and x3 - directions, respectively) - axial strain curve has a close similarity with the stress ratio - axial strain curve for the PSC test. The evolution of the coordination number and the sliding contact fraction is independent of the stress paths. A link between the macro- and micro-quantities is observed and a unique macro-micro relationship is noticed, regardless of the stress paths applied in this study.
Ključne besede: conventional triaxial compression, plane-strain compression, micro response, DEM
Objavljeno: 13.06.2018; Ogledov: 44; Prenosov: 0
.pdf Celotno besedilo (257,70 KB)

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