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The analysis of permanent deformations of repeatedly loaded gravels from the Mura region
Gregor Ficko, Bojan Žlender, 2005, original scientific article

Abstract: This contribution presents the results of the analysis of permanent deformations of gravel in the Mura region under repeated loading. The purpose of the analysis is to forecast the development of permanent normalised axial deformations ▫$/epsilon_1^{p*}$▫ regarding the number of loading cycles N and appurtenant stress states during cycling loading. The analysis used the results of tests performed by ZAG Ljubljana and Faculty of Civil Engineering and Geodesy (FGG) of the University of Ljubljana [1]. The analysis considers five types of stonematerials of different quantity of crushed grains in the mixture and of different water contents. Four types of stone materials are mixtures of different portions of crushed grains larger than 2 mm (Dcr = 87.7 %, 58.9 %, 32.6 % in 0 %), and of the water content around w = wopt - 2%. The stone material with portions of crushed grains larger than 2 mm Dcr= 58.9 % is analysed also for water content w = wopt + 0.7 %. The results of the analysis are deformations expressed as a function of the number of loading cycles N, and a spherical component of the repeated loading p and a distortional component of the repeated loading q. The results can be presentedas deformation surfaces in the ▫$/epsilon_1^{p*}$▫ - p - q space for an arbitrary number of cycles N. The relation between the spherical stress component p and the distortional stress component q, at arbitrary values of axial permanent deformations ▫$/epsilon_1^{p*}$▫, gives a failure envelope, and the so called deformation envelopes in the p - q space. The failure envelopes and deformation envelopes are given separately for five types of stone material. The deformation envelopes are low at small values of the axial permanent deformation ▫$/epsilon_1^{p*}$▫ When permanent axial deformations grow, the permanent deformation approaches the failure envelopes. The failure envelopes for individual types of stone material agree with research results performed by [1]. The analysis of permanent deformations also shows their dependence on the portion of crushed material Dcr in the mixture of crushed and uncrushed stone material. The deformation envelope for uncrushed stone material is situated in the lowest position, regarding the portion of crushed material in the mixture. With an increased portion of crushed material in the mixture of crushed and uncrushed stone material, the deformation envelope is also higher, similarly to the lawfulness of failure envelopes. The relation of failure and deformation envelopes is mathematically established as a function of the portion of crushed grains larger than 2 mm. The comparison of stone material results for different water contents shows that a minimal increase of water content above the optimal one essentially increases deformation.
Keywords: building materials, Mura river gravel, cyclic triaxial tests, granular base material, permanent deformation, normalized axial permanent deformation
Published: 01.06.2012; Views: 1125; Downloads: 31
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Impact of soil composition on fall cone test results : technical note
Bojana Dolinar, Ludvik Trauner, 2005, original scientific article

Abstract: The cone penetrometer method is being increasingly used for the determination of the liquid limit of cohesive soils. The same method can be used to determine the plastic limit according to the known relationship between soil moisture content and depth of cone penetration. This relationship is non-linear, yet becomes linear on a log-log scale resulting in a simple methodof determination of liquid limit and plastic limit values. This technical note determines the soil properties that define these index parameters. Experimentally obtained results suggest that the index parameters primarily depend on the type, size, and quantity of the clay minerals in soil.Soil index parameters such as the liquid limit and plastic limit can be determined from knowledge of the mineralogical properties of the soil because this dependence appears well defined.
Keywords: soil mechanics, soil tests, clays, cohesive soils, soil properties, Attenberg limits, cone penetration tests
Published: 01.06.2012; Views: 1379; Downloads: 30
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Efficiency of the coagulation/flocculation method for the treatment of dyebath effluents
Vera Golob, Aleksandra Vinder, Marjana Simonič, 2005, original scientific article

Abstract: Textile dyeing processes are among the most environment-unfriendly industrial processes, because they produce coloured wastewaters that are heavily polluted with dyes, textile auxiliaries and chemicals. The coagulation/flocculation method was studied as a wastewater treatment technique for the decolourization of residual dyebath effluents after dyeing cotton/polyamide blends using reactive and acid dyes. It was discovered that acombination of aluminium sulphate and a cationic organic flocculant yields an effective treatment for residual dyebath wastewaters since almost complete decolourization was achieved, TOC, COD, AOX, BOD and the anionic surfactants were reduced and the biodegradability was increased.
Keywords: textile industry, reactive dyes, acid dyes, wastewater, čiščenje odpadnih vodwastewater treatment, flocculation, coagulation, ecological analyses, wastewater decoloration, Jar-tests
Published: 01.06.2012; Views: 1518; Downloads: 66
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Reinforced prefabricated timber shear walls
Miroslav Premrov, Peter Dobrila, 2002, original scientific article

Abstract: The paper presents results of shear-bending experiments performed on panel shear walls used as load-carrying capacity walls in the construction of prefabricated timber structures. The aim of research is to determine the difference in resistance and ductility between panel shear walls, reinforced with two different methods. While the first, reinforcing with additional fiberboard, was not improve resistance and especially ductility in the contended sense, we tried to find a solution by inserting diagonal steel strips, which were fixed to the timber frame. Additionally, analytical solutions of those by mathematical modeling with the fictive thickness and height of fiber-plaster boards are proposed. Presented design models are simple and show a good coincidence with the measured results.
Keywords: timber structures, shear walls, shear bending tests, mathematical modelling
Published: 01.06.2012; Views: 1394; Downloads: 27
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Manipulation of chitosan binding on the polyethylene terephthalate (PET) surface and study of coatings on poultry meat shelf life-time
Tina Tkavc, 2014, doctoral dissertation

Abstract: The aim of this study was to activate inert PET surfaces in order to introduce the surfaces’ carboxyl groups and to obtain its hydrophilic character, which was important for the chitosan bonding to it. Films where chitosan was attached to the PET could be used as active packaging material for food like fresh poultry meat. For PET activation two advanced and environmentally friendly techniques were used: 1) O2 plasma activation; and 2) CO2 plasma activation. Differently treated PET foils deposited on Au quartz crystals (model studies - adsorption and desorption) and real films were characterized. Later on, real films were studied in the terms of carboxylic/amino group content, hydrophobic/hydrophilic character, surface composition and adsorption/desorption of chitosan onto/from the surface. Results clearly showed that the use of both surfaces’ activation processes increased the ability of PET foils to adsorb chitosan, but CO2 plasma gave a higher concentration of carboxyl groups on the PET surface and consequently, due to the chemical bonding the chitosan layers were more stable. Even though CO2 plasma pre-treated PET foils gave better results during the experimental work, we could not avoid layer by layer adhesion of chitosan which resulted in non-bound molecules. Pre-treated foils and with chitosan functionalized foils were tested preliminarily with ASTME E1 (2002) microbiological tests. Functionalized CO2 plasma pre-treated foils gave the broadest spectra of antimicrobial activity, and therefore they were chosen for further microbiological analyses, where chitosan`s influence on inoculated poultry models towards selected standard strains, typical for poultry meat, was being tested. By determining the MIC (minimal inhibitory concentration) for selected microorganisms we have proven, that chitosan possesses antimicrobial properties at low concentrations. During the transfer of the experiment to a larger scale (food models, which are a very complex environment), it has been shown that on PET bonded chitosan did not have the inhibitory effect to that extent, with the exception of Staphylococcus aureus, as was expected. Similar results were expressed using both these methods: Colony count technique and real-time PCR. In the end, the organoleptic properties of the chicken models exposed to foils have shown that chitosan changes the color and taste of meat immediately after exposure, but samples were staying edible longer. Therefore, functionalized PET, which has an inhibitory influence towards variety of microorganisms, may be applied as an active packaging system for poultry meat after some optimization of the coating procedure in binding chitosan onto the PET surfaces.
Keywords: PET/chitosan/antimicrobial packaging/adsorption-desorption kinetics/microbiological tests
Published: 22.10.2014; Views: 1438; Downloads: 140
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Validity of the “fall back” test for boldness
Saša Veličković, Miloš Paunović, Vladan Vukašinović, 2016, original scientific article

Abstract: Synonyms for the word boldness include courage, fearlessness, heroism and bravery. The best examples of courage in sport are athletes who, despite difficult situations, conditions and strong competition, perform very risky elements, break records, etc. The "Fall back" measurement instrument has been used in the selection process for artistic gymnastics. Bearing in mind that this test requires a drop back down an inclined plane, it requires a degree of courage in the realization of this motor task. The aim of this research is to determine the validity of the "fall back" test and to answer the question: Is the "Fall back" test actually a measure of courage among beginners in the sport? In this study, the research sample consisted of 16 boys and 33 girls, third graders from the Jovan Cvijic elementary school in Kostolac, aged nine years (+/- 6 months). The sample of variables represented the results written using two measurement instruments: 1. Psychological survey -test of boldness and courage - PSBC (a test modeled after the - Erikson`s theory of Psyhosocial Development test - About.com Psyhology); 2. Situational motor measuring instrument - Fall back - MFIB. The resulting measurements were analyzed by the appropriate statistical methods, which are congruent with the set objective and task ofthe study. The validity of the "Fall back" situational-motor test is determined by calculating the coefficient of correlation (r) between said composite test and a psychological test of courage. The very high coefficients of correlation that resulted in all three cases (total sample r = .846, sample of boys r = .873, a sample of girls r = .845) indicate a high validity level for the test, "Fall back", that is, the subject of measurement in the test, largely corresponds with the subject of measurement in the PSBC psychological test. The height of the correlation coefficient also justifies the use of the "Fall back" test as a composite test. A high validity of the "Fall back" measurement instrument (MFIB), which is indicated by the high Pearson coefficients of correlation between the"Fall back" measurement instruments and the psychological test of courage and boldness, was established for all three samples of respondents.
Keywords: boldness, tests, fall back, validity
Published: 11.10.2017; Views: 491; Downloads: 46
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Cyclic liquefaction potential of lacustrine carbonate from Julian Alps
Bojan Žlender, Stanislav Lenart, original scientific article

Abstract: This paper presents the liquefaction studies of lacustrine carbonate silt from the Julian Alp landslide Stože. Geological conditions of the region and geomechanical characteristics of the ground were investigated. The research project was performed with the intention to determine the effects of cyclic loading on lacustrine carbonate silt. Investigation with 77 cyclic triaxial tests was performed on universal triaxial apparatus Wykeham Farrance UP 100 TR, in the Laboratory of soil mechanics, Faculty of Civil Engineering, University of Maribor. The essential equipment comprises cylindrical triaxial apparatus with a cell, a press with appurtenant electro-mechanic equipment, measuring equipment, and computer hardware and software equipment. Specimens with dimensions of height = 140 mm and diameter = 70 mm were saturated, then subjected to the arbitrary initial isotropic stress state and consolidated with vertical and radial draining, and then loaded with distortional loading of chosen dynamical axial force (frequency f = 1 Hz). A set of tests with a spectrum of different stress states and cyclic loading were performed. This research showed that lacustrine carbonate silt is a highly sensitive material.The resistance to liquefaction was somewhat higher than that of typical clean sand, but a perceivable excess pore pressure generation, which causes the decrease of strength parameters, was noticed. Test results of cyclic triaxial tests indicate dynamic characteristics of lacustrine carbonate silt and wide applicability of the test method.
Keywords: civil engineering, geomechanics, soil investigations, lacustrine carbonate silt, cyclic triaxial tests, liquefaction potential, shear modulus, damping ratio, cyclic stress ratio, pore pressure ratio
Published: 15.05.2018; Views: 469; Downloads: 28
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Influence of mould suction on the volume - change behaviour of compacted soils during inundation
Matej Maček, Bojan Majes, Ana Petkovšek, 2011, original scientific article

Abstract: After construction, compacted clayey soils in different earth structures equilibrate their water content and suction with the local environment. In wet climatic conditions the compaction on the dry side of the Proctor curve, which enables a high layer stiffness during construction, may result in permanent deformation and softening during the lifetime of the structure. This paper presents the results of the tests, performed on a relatively large number of compacted test specimens, where the conventional index parameters, used to identify compacted soils, were supplemented with a suction–water-content curve and measurements of “mould” suction. Correlations were established between the optimum water content and the suction–water-content curve for representative samples, and the influence of the mould suction on the vertical deformation of the compacted samples during inundation in oedometers was studied.
Keywords: oedometer tests, suction, swelling, collapse
Published: 13.06.2018; Views: 235; Downloads: 55
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Determination of the fabric alteration of marine clays
Suchit Gumaste, 2014, original scientific article

Abstract: 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.
Keywords: marine clays, anisotropy, laboratory tests
Published: 14.06.2018; Views: 249; Downloads: 36
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Quality control for the construction of a tailings dam
Wojciech Tschuschke, Magdalena Wróżyńska, Jędrzej Wierzbicki, 2017, original scientific article

Abstract: Every day the mining industry produces large amounts of mine tailings. In the case of copper ores exploited in Poland, the post-flotation tailings constitute 95% of the excavated rock and all the tailings are deposited in dumps, which are supported by outer dams. The durability and stability of these earth structures determine the safe operation of the entire object. The selection of adequate-quality soils for the construction of the dams is a crucial factor limiting the risk of its potential failure. Very large depositories require sufficiently large amounts of soil for the construction of the dams. An alternative to this classic approach is the use of the deposited tailings. In this solution the amount of mine wastes stored in the depository is reduced, there is no need to exploit the deposits of natural soils and the potential capacity of the depository increases. This paper presents the principles of the construction technology for hydraulically filled dams; the criteria for the selection of proper soil gradation and the physical properties of the sediments to be used in the construction of the dams; the principles of quality control for earth works; and the methodology of the geotechnical control tests. The effects of the applied technology on the condition of the natural environment are also discussed.
Keywords: post-flotation sediments, tailings dams, geotechnical control tests
Published: 18.06.2018; Views: 296; Downloads: 29
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