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The complexity of porous structure of building materials
Marko Samec, 2011, doktorska disertacija

Opis: This thesis seeks to establish the link between the structure (in a topological sense) of porous space and charged particle dynamics in porous matter, specifically in constituent elements of sustainable building materials such as clay, cement and soil. The work done is a combination of experimental research and modelling of analysed data using advanced and expanded network models to model pore structure and generalized conductivity model. The main outcome of this doctoral thesis is the demonstration that there is a correlation between the large scale structure of the pore space and the properties of the motion of charged particles through the pore space. This was achieved by conducting two experiments: the structure of pore space of selected porous materials (soil samples, clays, cements, clay-cement mixtures) was investigated using state-of-the-art X-ray computed microtomography, while the dynamics of charged particles in the samples was probed using low-frequency dielectric spectroscopy. The research done and described in the thesis is directed towards the advancement of understanding the transport phenomena and the structure of porous media which is of paramount importance for solving problems in building physics dealing with moist transport in building's envelope, the building-ground interaction, and in transport of contaminants in the vicinity of the repositories where the transfer of moist through soil can be the source of contamination.
Ključne besede: porous matter, clay-water system, hydrating cement, fractional dynamics, dielectric response, X-ray computed tomography, image analysis, complex network
Objavljeno: 11.05.2011; Ogledov: 3396; Prenosov: 146
.pdf Celotno besedilo (34,69 MB)

The impact of structure on the undrained shear strength of cohesive soils
Bojana Dolinar, Ludvik Trauner, 2007, izvirni znanstveni članek

Opis: The relationship between the undrained shear strength and the water content ofcohesive soils can be described with a two parameter non-linear function. Parameter a is the water content at the undrained shear strength su=1 kPa, andb is the slope of the linear function which represents the ratio between the water content logarithm and the undrained shear strength logarithm. These parameters depend mainly on the type and amount of clay minerals in the soils,the particle sizes and shapes, their arrangements, the forces between the clay particles, and the chemical composition of the pore water. The impactof quantity, type and size of clay grains on the water content at a uniform undrained shear strength in different soils has been studied previously, whilst the impact of structure is less understood. Particle associations and arrangements (i.e. fabric), and the interparticle forces determine the structure of soil. This paper focuses on an investigation of therelationship between water content and undrained shear strength in kaolinite samples with different structures. The various arrangements of clay particles that resulted from the changed of interparticle forces were obtainedby salt addition (NaCl). Microfabrics of wet kaolinite samples were studied using a field emission scanning electron microscope. The results showed that clay structure exerts a strong influence on the relationship between the quantity of water and undrained shear strength. This was reflectedin the values of both soil-dependent parameters, a and b. Values of parameter a varied between 39.16% and 62.96%, and b between 0.100 and 0.139, for well crystallized kaolinite with salt concentrations of 0- 175 mmol/l. Forpoorly crystallized kaolinite with salt concentrations of 0-300 mmol/l, thevalues of a range between 46.96% and 100.30%, and b between 0.090% and 0.148%.
Ključne besede: geomechanics, clay, kaolonite, structure, fabric, undrained shear strength
Objavljeno: 31.05.2012; Ogledov: 1232; Prenosov: 37
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Polymer nanocomposite hydrogels for water purification
Manja Kurečič, Majda Sfiligoj-Smole, 2012, samostojni znanstveni sestavek ali poglavje v monografski publikaciji

Ključne besede: polymer nanocomposites, wastewaters, coloures wastewaters, clay minerals, dye adsorption, hydrogels
Objavljeno: 10.07.2015; Ogledov: 443; Prenosov: 21
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An evaluation of marine sediments in terms of their usability in the brick industry
Patrik Baksa, Franka Cepak, Rebeka Kovačič Lukman, Vilma Ducman, 2018, izvirni znanstveni članek

Opis: A dredging process is essential for the development of harbours and ports, allowing the functional daily operation of the port. The management of dredged material represents a worldwide challenge, especially considering unwanted deposition of material. Because of their chemical, petrographic, mineralogical and homogeneity composition, marine sediments could represent an appropriate raw material for the brick industry, particularly for the production of clay blocks, roofing and ceramic tiles. In this study dredged material from Port of Koper was tested for such use, thus various analyses were carried out in order to determine if the dredged material is environmentally friendly and suitable for use in the brick industry. These included: chemical analysis, mineralogical analysis, particle size analysis, chloride content analysis and tests of firing in a gradient furnace. Furthermore, tests of mechanical properties, as well as tests of the frost-resistance of the samples were carried out. On the basis of the primary analyses and samples prepared in a laboratory, it was confirmed that marine sediments from the Port of Koper, without any additives are only conditionally suitable as a source material for producing brick products, because without additives they exhibit too much shrinkage on drying and firing, as well as high water absorption, this can be improved by the incorporation of suitable additives, for example, virgin clay or other suitable waste material. The approach described herewith can also be followed to assess sediments from other ports and rivers regarding its potential use in clay brick sector.
Ključne besede: dredge marine sediment, recycling, clay bricks, mechanical properties, chemical analysis
Objavljeno: 21.12.2017; Ogledov: 668; Prenosov: 42
.pdf Celotno besedilo (447,79 KB)
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Influence of geosynthetic reinforcement on the shear strength characteristics of two-layer sub-grade
Mehrad Kamalzare, Reza Ziaie-Moayed, 2011, izvirni znanstveni članek

Opis: Due to the low bearing capacity of soft clayey soils in places that because of economic, military or geological conditions we are oblige to build a structure on, geosynthetics will be used to reinforce the soil and improve its bearing capacity. Particularly, A good example is roadways, where geosynthetics are placed between the interface of the granular materials and the soft-soil sub-grade to improve the bearing capacity of the composite layers. In previous research the behavior of one-layer soils that were reinforced with different kinds of geosynthetics were studied by experimental and analytical methods and some numerical models have been developed. In this paper the behavior of two-layer soils (granular base and clayey sub-grade) that were reinforced with some geosynthetics are investigated. Large-scale direct shear tests were performed on unreinforced and reinforced samples with different geosynthetics. The results show that depending on the characteristics of the geosynthetics, the inclusion of these materials may increase or decrease the shear strength parameters of the interface of two-layered soils. It implies that the geosynthetic-reinforced soils in the sub-base layer of roads are so sensitive to the characteristics of geosynthetics and will perform better than non-reinforced soils and consequently the load-carrying capacity of the basement will improve only if the appropriate geosynthetics are used. However, geogrid shows more reinforcement efficiency under higher vertical stresses. Increasing the relative density of the clayey sub-grade would also cause the geogrid reinforcement to be more effective.
Ključne besede: shear strength, geosynthetic, large scale direct shear test, soft clay, subgrade
Objavljeno: 13.06.2018; Ogledov: 84; Prenosov: 15
.pdf Celotno besedilo (1,52 MB)
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Numerical analysis of circular footings on natural clay stabilized with a granular fill
Murat Ornek, Mustafa Laman, Ahmet Demir, Abdulazim Yildiz, 2012, izvirni znanstveni članek

Opis: In this study, numerical predictions of the scale effect for circular footings supported by partially replaced, compacted, layers on natural clay deposits are presented. The scale- effect phenomenon was analyzed according to the footing sizes. Numerical analyses were carried out using an axisymmetric, two-dimensional, finite-element program. Before conducting the analysis, the validity of the constitutive model was validated using field tests performed by authors with seven different footing diameters up to 0.90 m and with three different partial replacement thicknesses. It is shown that the behavior of the circular footings on natural clay soil and the partial replacement system can be reasonably well represented by the Mohr Coulomb model. The Mohr-Coulomb model parameters were derived from the results of conventional laboratory and field tests. After achieving a good consistency between the results of the test and the numerical analysis, the numerical analyses were continued by increasing the footing diameter up to 25 m, considering the partial replacement thickness up to two times the footing diameter. The results of this parametric study showed that the stabilization had a considerable effect on the bearing capacity of the circular footings and for a given value of H/D the magnitude of the ultimate bearing capacity increases in a nonlinear manner with the footing diameter. The Bearing Capacity Ratio (BCR) was defined to evaluate the improved performance of the reinforced system. It was found, based on numerical and field-test results that the BCR of the partially replaced, natural clay deposits increased with an increase in the footing diameter and there was no significant scale effect of the circular footing resting on natural clay deposits.
Ključne besede: scale effect, circular footing, field test, finite-element analysis, natural clay, granular fill
Objavljeno: 13.06.2018; Ogledov: 65; Prenosov: 15
.pdf Celotno besedilo (554,10 KB)
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A simplified approach to the settlement estimation of piled rafts
Volkan Kalpakci, Mehmet Yener Özkan, 2012, izvirni znanstveni članek

Opis: In this study, a simplified approach to the settlement estimation of piled rafts resting on over-consolidated clay deposits is presented. For this purpose, a series of plane-strain and three-dimensional analyses were performed and their results are compared with the available data in the literature. It was found that the percentage decrease in the total settlements with the addition of piles with respect to the unpiled case is very closely estimated by both the plane-strain and the three-dimensional, simplified, numerical analyses. Using this phenomenon, a simple method of analysis is suggested for the total settlement estimation of the piled raft foundations and design charts are provided for the cases studied (for the specific soil conditions only) throughout this study.
Ključne besede: piled rafts, settlement, over-consolidated clay, foundation design
Objavljeno: 13.06.2018; Ogledov: 114; Prenosov: 16
.pdf Celotno besedilo (481,96 KB)
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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: 155; Prenosov: 12
.pdf Celotno besedilo (727,36 KB)
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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: 159; Prenosov: 16
.pdf Celotno besedilo (676,68 KB)
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