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61.
Determination of the fabric alteration of marine clays
Suchit Gumaste, 2014, izvirni znanstveni članek

Opis: This paper presents details of investigations that were conducted to determine the fabric (i.e., the arrangement of soil grains and pores) of undisturbed marine clay samples that were retrieved from 5 m to 65 m below the seabed. Impedance Spectroscopy (IS), which is a non-destructive and non-invasive technique, was employed to determine the electrical conductivities of the marine clay samples in their longitudinal and transverse planes of sedimentation. These results were employed to define the extent of the fabric anisotropy in terms of an anisotropy coefficient, Ae, as a function of depth. In addition, Scanning Electron Microscopy (SEM) and Mercury Intrusion Porosimetry (MIP) were employed to study the fabric and pore-size distribution of these samples, respectively. Based on these investigations it has been observed that Ae increases with sampling depth, which is indicative of the alteration from flocculated fabric, at shallower depths, to the dispersed fabric, at deeper depths. The study highlights the importance and usefulness of the anisotropy coefficient, Ae, for determining the alteration in the fabric of marine clays, due to self-weight consolidation.
Ključne besede: marine clays, anisotropy, laboratory tests
Objavljeno: 14.06.2018; Ogledov: 8; Prenosov: 0
.pdf Celotno besedilo (399,08 KB)

62.
Numerical simulation of the pile integrity test on defected piles
Mladen Ćosić, Boris Folić, Radomir Folić, 2014, izvirni znanstveni članek

Opis: This paper deals with the development of a discrete numerical 2D and 3D solid pile model with a discontinuity and defects to simulate non-destructive testing using the pile integrity test (PIT). The pile discontinuity and defects were modelled by reducing the specific finite elements and the elastic modulus of concrete. The wave-propagation response of the pile was analyzed based on a step-by-step numerical integration using the Hilber-Hughes-Taylor (HHT) method in the time domain. The concept of a system-response analysis was originally formulated based on the integration of individual reflectograms into a reflectogram surface, which is generated in a 3D cylindrical coordinate system. The use of reflectogram surfaces enables an understanding of wave propagation based on their velocity to a higher level than is usually the case with standard, one-dimensional reflectograms. Changes in the velocity responses on the reflectogram, shifting from a positive to a negative value, point to the locations of discontinuities and defects in the discrete 3D pile model, and there is a clear difference in the reflectograms, depending on the position of the measuring point. The study defines the typological models of the reflectogram: without discontinuities and defects, pile-head defect, defect in the middle of the pile length or a reduced modulus of elasticity in the middle of the pile length, pile-base defect or reduced modulus of elasticity in the pile-base zone and reduced modulus of elasticity in the pile-head zone.
Ključne besede: reflectogram surface, numerical pile model, solid finite elements
Objavljeno: 14.06.2018; Ogledov: 8; Prenosov: 0
.pdf Celotno besedilo (769,91 KB)

63.
Editorial
Bojana Dolinar, 2014, predgovor, spremna beseda

Ključne besede: editorials, scientific journals, geomechanics, geotechnical engineering
Objavljeno: 14.06.2018; Ogledov: 12; Prenosov: 1
.pdf Celotno besedilo (32,36 KB)
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64.
Formation of meso- and micro-pores in fly-ash zeolites using a three-step activation
Bhagwanjee Jha, D. N. Singh, 2014, izvirni znanstveni članek

Opis: Researchers have comprehensively characterized alkali- activated fly-ash (the residue) and ascertained its highly zeolitic nature. In order to evaluate its potential for application as an adsorbent for the decontamination of waste water, the decisive parameters have mostly been the cation-exchange capacity, the mineralogy and the morphology of the residue. However, a study of the pore characteristics (e.g., the size and volume) of such residues is still warranted to anticipate their contaminant transport and the diffusion phenomena as a type of geotechnical engineering material. In this situation, the present study demonstrates the evolution of pores in the fly-ash after alkali activation up to three steps, and simultaneously, its effects` on other characteristics (e.g., the specific gravity, specific surface area and the cation-exchange capacity) of three types of similarly synthesized residues (the first, produced by using a NaOH aqueous solution and the other two residues, the result of alkali activation using a NaOH spent solution, the filtrates). Based on N2 gas absorption isotherms and infrared transmittance spectra, residues obtained from the second and third steps, each involving 24 hours of treatment using filtrates of 1.5-M NaOH, are established to be significantly enriched in the finer meso- and micro-pores, respectively, in comparison with a pure and macro-porous zeolite 4A.
Ključne besede: fly-ash, hydrothermal treatment, three-step activation, pore characteristics
Objavljeno: 14.06.2018; Ogledov: 11; Prenosov: 0
.pdf Celotno besedilo (298,21 KB)

65.
Analytical solutions for one-dimensional consolidation in unsaturated soils considering the non-Darcy law of water flow
Jiwei Li, Huabin Wang, 2014, izvirni znanstveni članek

Opis: Analytical solutions were derived for the non-linear, one-dimensional consolidation equations for unsaturated soils. The governing equations with a non-homogeneous mixed-boundary condition were presented, in which the water flow was assumed to be governed by a non-Darcy law, whereas the air flow followed the Darcy law. The non-Darcy law was actually the non-linear, flux-gradients relationship. The consolidation equations were thus present in a strong, non-linear way. In order to analytically solve the equation, a homotopy analysis method (HAM) was introduced in the study, which is an analytical technique for nonlinear problems. Firstly, a governing equation in a dimensionless form was derived for a one-dimensional consolidation under unsaturated soils. The method was then used for a mapping technique to transfer the original nonlinear differential equations to a number of linear differential equations. These differential equations were independent with respect to any small parameters, and were convenient for controlling the convergence region. After this transferring, a series solution to the equations was then obtained using the HAM by selecting the linear operator and the auxiliary parameters. Meanwhile, comparisons between the analytical solutions and the results of the finite-difference method indicate that the analytical solution is more efficient. Furthermore, our solutions indicate that the dissipation of air pressure is much faster than that of water pressure, and the values for the threshold gradient I have obvious effects on the dissipation values of the excess pore-water pressure, but no significant effect on that of the excess pore-air pressure.
Ključne besede: unsaturated soil, homotopy analysis method, analytical solutions, non-Darcy law, initial and boundary conditions
Objavljeno: 14.06.2018; Ogledov: 10; Prenosov: 0
.pdf Celotno besedilo (295,39 KB)

66.
High safety pillars stability control using EL beam displacement sensors in Lipica II quarry
Jože Kortnik, Sunny Nwaubani, Andrej Kos, 2014, izvirni znanstveni članek

Opis: In underground Lipica II. quarry for the excavation of natural stone, a modified room-and-pillar mining method is used, that is adjusted to the conditions of the site. In order to support and ensure the stability of underground chambers high safety pillars (HSP) are used. These pillars are made of surrounding stone and therefore intersected by discontinuities. The discontinuities represent high risk to the stability of underground facilities and workmen below/ itself. To ensure their safety the stress and strain parameters in height safety pillars are continuously monitored using two vibrating wire (WV) stressmeters inside the high safety pillars and two EL (Electronic level) beam sensors on the surface of the high safety pillar VS3. In the time period October 2010/June 2012 absolute max. measured deviation with EL beam sensors were D1=0.9 mm and D2=1.1 mm, which does not compromise the stability of the high safety pillar VS3. This paper presents the procedures of wedges deformation monitoring in safety pillars with EL beam sensors in the Lipica II underground natural stone quarry.
Ključne besede: beam sensor, high saftey pillar, monitoring, natural stone, room and pillar mining method
Objavljeno: 14.06.2018; Ogledov: 8; Prenosov: 0
.pdf Celotno besedilo (491,51 KB)

67.
Settlement of weakly cemented tufas
Nihat Dipova, Ergun Ufuk, Doyuran Vedat, 2014, izvirni znanstveni članek

Opis: Weakly cemented tufas are sand and silt size soils that are weakly bonded with thin films of carbonate cement. The void ratio is rather high and equal to approximately 1.2. Collapse occurs as a result of the destruction of the weak bonds upon loading and/or wetting. The index properties and the collapse potential (Cp) of tufa were determined in the laboratory. In the determination of the collapse-potential values the single-ring oedometer method was considered to be a suitable and simpler tool. In plotting the oedometer test results the use of a natural scale was preferred over a logarithmic scale so that the void ratio-pressure relationship is polynomial. Under loading the soil settles with the natural water content; however, saturation increases the collapse that is initially triggered by the pressure increase. The pressure level is a significant parameter in the magnitude of the collapse and therefore in the total settlement. The settlement of foundations due to a collapse of the soil structure can be estimated directly using the oedometer test results and empirically using the index properties, like the initial void ratio (e0), the difference in the fine content between the dry and the wet sieve analyses (PFAW) and the natural unit weight. A comparison of the direct and empirical approaches yielded a good agreement.
Ključne besede: Antalya, collapse potential, collapsible soils, settlement, tufa
Objavljeno: 14.06.2018; Ogledov: 13; Prenosov: 0
.pdf Celotno besedilo (454,12 KB)

68.
Effects of ground granulated blast-furnace slag on the index and compaction parameters of clayey soils
Osman Sivrikaya, Selman Yavascan, Emre Cecen, 2014, izvirni znanstveni članek

Opis: The use of industrial wastes in soil stabilization not only provides for the re-use of waste materials, which may cause environmental pollution, but also leads to cost benefits. In this context, the use of industrial wastes in the stabilization of fine-grained soils has become a research topic in recent years. The aim of this study is to evaluate the potential use of granulated blast-furnace slag (GBFS) in clayey soil stabilization. In this study, the GBFS obtained from the Iskenderun iron-steel plant as an industrial waste was ground into two different fineness levels, and the effects of their incorporation into low-plasticity Kolsuz clay and high-plasticity bentonite clay in various rates (5%, 10%, 20%, 30%, and 50%) on the particle weight of unit volume, the consistency limits, and the compaction parameters are investigated. Based on the experimental results, it is clear that the GBFS has a positive effect on the stabilization of both clayey soils. It was also concluded that the improvement in bentonite clay is greater than that in Kolsuz clay. Thus, GBFS seems to be a promising material for the stabilization of clayey soils.
Ključne besede: clayey soils, index properties, granulated blast-furnace slag, stabilization
Objavljeno: 14.06.2018; Ogledov: 9; Prenosov: 0
.pdf Celotno besedilo (134,83 KB)

69.
Time-dependent behaviour of reinforced cuts in weathered flysch rock masses
Mirko Grošić, Željko Arbanas, 2014, izvirni znanstveni članek

Opis: Knowledge of stress-strain rock mass behaviour is crucial for many engineering purposes. Rock mass deformations and their influences on construction are observed during construction and even during exploitation phases. These deformations in the exploitation phase are caused by the time-dependent behaviour of the rock mass. A flysch rock mass is categorised as a heterogenic weak rock that has been intensely subjected to weathering processes. Due to weathering processes, the flysch rock mass degrades from fresh rock to residual soil within only a few meters of the geological profile below the surface. Observations of reinforced cuts along the Adriatic motorway near the City of Rijeka, Croatia, were conducted over a time period of seven years of spanning construction and exploitation. Measured displacements reached significant magnitudes during the exploitation period as a consequence of the time-dependent behaviour of the rock mass. The paper presents findings related to flysch rock mass weathering profile and its characteristics based on detailed geotechnical investigations and monitoring results coupled with back analyses. It was found possible to detect the thickness of the flysch rock mass weathering profile by performing detailed geotechnical investigations. Recommendations for the strength, deformation, and creep properties of the weathering profile of a flysch rock mass are given.
Ključne besede: time-dependent behaviour, weathering, weak rock mass, Burger model, back analyses
Objavljeno: 14.06.2018; Ogledov: 8; Prenosov: 0
.pdf Celotno besedilo (700,29 KB)

70.
Editorial
Bojana Dolinar, 2014, predgovor, spremna beseda

Ključne besede: editorials, scientific journals, geomechanics, geotechnical engineering
Objavljeno: 14.06.2018; Ogledov: 6; Prenosov: 0
.pdf Celotno besedilo (29,62 KB)
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