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51.
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: 6; Prenosov: 0
.pdf Celotno besedilo (298,21 KB)

52.
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: 6; Prenosov: 0
.pdf Celotno besedilo (295,39 KB)

53.
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: 6; Prenosov: 0
.pdf Celotno besedilo (491,51 KB)

54.
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: 6; Prenosov: 0
.pdf Celotno besedilo (454,12 KB)

55.
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: 7; Prenosov: 0
.pdf Celotno besedilo (134,83 KB)

56.
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: 6; Prenosov: 0
.pdf Celotno besedilo (700,29 KB)

57.
Editorial
Bojana Dolinar, 2014, predgovor, spremna beseda

Ključne besede: editorials, scientific journals, geomechanics, geotechnical engineering
Objavljeno: 14.06.2018; Ogledov: 4; Prenosov: 0
.pdf Celotno besedilo (29,62 KB)
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58.
Investigations to establish the influence of the thermal energy field on soil properties
Srinivas Kadali, Susha Lekshmi, Susmita Sharma, D. N. Singh, 2013, izvirni znanstveni članek

Opis: This paper describes details of a study to investigate and demonstrate the changes undergone by soil when it is exposed to elevated temperatures. Such situations are commonly encountered while designing the foundations for the furnaces, boiler units, forging units, brick kilns, rocket launching pads, buried power-supply cables, air-conditioning ducts, underground explosions, disposal of high-level radioactive and industrial toxic wastes, ground modifications or soil-stabilization techniques, etc. As such, investigations to establish changes undergone by the soil when it is exposed to elevated temperatures assume some importance. With this in view, individual samples of six soils, with entirely different characteristics, were subjected to temperatures up to 300°C (sequentially in steps of 50°C) and after each step of thermal treatment, these samples were characterized for their physical, chemical and mineralogical properties. Based on a critical synthesis of the results, it has been demonstrated that elevated temperatures cause (i) a change in the color, (ii) an increase in the specific gravity, particle size and weight loss, (iii) a reduction in the specific surface area, cation-exchange capacity and zeta-potential, and (iv) a structural transformation of the soil. Though these changes would affect the engineering properties of the soil to a large extent, the scope of this paper is limited to demonstrating the alterations in physical, chemical and mineralogical changes, only, occurring in the soil when it is exposed to elevated temperatures.
Ključne besede: elevated temperatures, soil, characterization, physical characteristics, chemical characteristics, mineralogical characteristics
Objavljeno: 14.06.2018; Ogledov: 3; Prenosov: 0
.pdf Celotno besedilo (1,08 MB)

59.
Evolutionary-based prediction of ε50 for the lateral load-displacement behavior of piles in clay
Babak Ebrahimian, Aida Nazari, 2013, izvirni znanstveni članek

Opis: Analyzing piles that are subjected to lateral loads reveals that their behavior depends on the soil’s resistance at any point along the pile as a function of the pile’s deflection, known as the p-y curve. On the other hand, the deformation characteristics of soil defined as “the soil strain at 50% of maximum deviatoric stress (ε50)” have a considerable effect on the generated p-y curve. In this research, several models are proposed to predict ε50 specifically for designing the very long pile foundations of offshore oil and gas platforms in the South Pars field, Persian Gulf, Iran. Herein, ε50 is evaluated using extensive soil data, including in-situ and laboratory test results using evolutionary polynomial regression (EPR). The effects of the undrained shear strength, the normalized tip resistance of the cone penetration test, the over-burden pressure, the plasticity index and the over-consolidation ratio on ε50 are investigated in marine clays. It is demonstrated that the normalized cone tip resistance, which is an indication of the soil’s undrained shear strength, leads to more realistic ε50 values compared with the laboratory-derived undrained shear strength parameter. In addition, the application of the soil-index properties and the over-burden pressure in the models, improves their estimation quality. Furthermore, the results of full-scale lateral pile load tests at different sites are used in order to validate the performance of the proposed models when it comes to predicting the behavior of the lateral piles.
Ključne besede: p-y curve, laterally loaded pile, piezocone penetration test, PCPT, marine clay, evolutionary polynomial regression, EPR, South Pars field
Objavljeno: 14.06.2018; Ogledov: 4; Prenosov: 0
.pdf Celotno besedilo (676,68 KB)

60.
Prediction of the compaction parameters for coarse-grained soils with fines content by MLA and GEP
Osman Sivrikaya, Cafer Kayadelen, Emre Cecen, 2013, izvirni znanstveni članek

Opis: The determination of the compaction parameters of soils, the maximum dry unit weight (γdmax) and the optimum water content (wopt), at various compaction energy (E) levels is an important process. The aim of this study is to develop correlations in order to estimate the compaction parameters dependent on the compaction energy for coarse-grained soils with various fines contents on which limited studies exist in the literature. Genetic Expression Programming (GEP) and Multi Linear Regression (MLR) analyses are used in the derivation of the correlations for the prediction of γdmax and wopt obtained from Standard Proctor (SP) and Modified Proctor (MP) tests with the index properties of coarse-grained soils with various fines contents. To develop the models, a total of 86 data sets collected from university laboratories in Turkey and six parameters, such as gravel content (G %), sand content (S %), fines content (FC %), liquid limit (wL %) and plasticity index (IP %) of fines content and compaction energy (E Joule), are used. The performance of the models is comprehensively examined using several statistical verification tools. The results revealed that the GEP and MLR models are fairly promising approaches for the prediction of the maximum dry unit weight and the optimum water content of cohesionless soils with various fines contents at SP and MP compaction energy levels. The proposed correlations are reasonable ways to estimate the compaction parameters for the preliminary design of a project where there are financial and time limitations.
Ključne besede: coarse-grained soils, compaction, MLR, GEP
Objavljeno: 14.06.2018; Ogledov: 3; Prenosov: 0
.pdf Celotno besedilo (360,65 KB)

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