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The influence of porosity on geomechanical characteristics of snail soil in the Ljubljana Marsh
Bojan Žlender, Ludvik Trauner, 2006, izvirni znanstveni članek

Opis: This article focusses on mineralogical and physical characteristics of snail soil and their influence on parameter values of geomechanical characteristics.Snail soil, which got its name from fossil remains, is a typical layer observed in the Ljubljana marsh. It is distincltly porous, saturated and in a liquid consistency state. Snail soil was investigated for mineralogical and physical characteristics in the Laboratory of Soil Mechanics, Faculty of Civil Engineering of the University in Maribor. Mineral and chemical composition, visual appearance, specific surface and grain property were determined. Physical characyteristics show that snail soil is saturated in nature, highly porous and almost liquid. Geomechanical characteristics were investigated for their interdependency on physical characteristics. A series of triaxial tests were performed on snail soil samples of different porosity, density and water content. Cylindrical samples of the height of 100 mm and the diameter of 50 mm were tested using three-axial testing apparatus. The results of the tests show that interdependency exists between geomechanical characteristics and porosity. These relationships can be expressed as functions of density, porosity or water content. It is evident from the results that changes of the coefficient of permeability, the coefficient of consolidation, and the coefficient of volume compressibility are nonlinear with respect to changes in porosity. Changes of mechanical parameters, such as Young`s modulus, Poisson`s ratio andfriction angle are indistinct and almost linear at lower changes of porosity.
Ključne besede: geomechanics, properties of soils, snail soil, triaxial testing, porosity, permeability, consolidation, Young`s modulus, Poisson`s ratio, shear angle
Objavljeno: 17.05.2018; Ogledov: 323; Prenosov: 23
.pdf Celotno besedilo (486,06 KB)
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The dynamic properties of the snail soil from the Ljubljana marsh
Bojan Žlender, Ludvik Trauner, 2007, izvirni znanstveni članek

Opis: A series of cyclic triaxial tests was performed on snail-soil samples with different porosities. The cyclic loading was performed with a Wykeham Farrance cyclic triaxial system. The investigation was based on a series of tests in which the following conditions were varied: the initial effective pressures (50, 100, and 150 kPa), the void ratio after consolidation (2.0–1.2) and the cyclic loading expressed by the cyclic stress ratio CSR (0.1–1.0). Measurements were made of the stress, the deformation and the pore-water pressure. The results of the tests show that interdependency exists between the geomechanical characteristics and the porosity. These relationships can be expressed as functions of the density, the porosity or the water content. It is evident from the results that the changes in the coefficient of permeability, the coefficient of consolidation, and the coefficient of volume compressibility are non-linear with respect to the changes in the porosity. However, the changes at high porosity are much greater than the changes at low porosity, and the changes of the mechanical parameters, such as the Young’s modulus, Poisson’s ratio, and the friction angle, are indistinct and almost linear at lower changes of porosity, and after that become non-linear. The initial void ratio e is extremely high and the snail soil is liquid after consolidation; a volume strain of εvol > 16 % is needed for the plastic limit state. The chemical and mineral composition, the particle size distribution and the remains of micro-organisms in the snail soil are constants. In addition, the specific surface is independent of the porosity and the density or unit weight, the porosity and the volume strain are in the well-known correlation. The performed cyclic triaxial tests show the dynamic characteristics of the snail soil and the influence of the porosity on the cyclic loading strength. The snail soil was recognized as a highly sensitive material. A large strain appears after the initial cycles. The pore pressure, increases already during the first cycle, to the hydrostatic part of the cyclic loading, or more (depending on CSR). The damping ratio increases exponentially with strain, after some cycles it reach its maximum value, and after that it decreases to the asymptotic value. The reason for such behaviour is the large deformation. The maximum and asymptotic values of the damping ratio are a changed minimum with a void ratio. There is obviously no influence of the porosity on the damping ratio. The shear modulus is described in relation to shear strain. The increasing of the pore pressure is independent of the porosity until it reaches some value of the pore-pressure ratio (>0.7). Similarly, the increasing of the shear strain becomes dependent on the void ratio until it reaches some particular value of the shear strain (>3%). The deformation and failure lines for the different porosities are determined from the relationship between the shear stress and the effective stress at some shear strain, after 10 cycles. The relationships between the shear stress and the effective stress at some value of the pore-pressure ratio are expressed in a similar way. Two kinds of criteria were used to determine the triggering of liquefaction during the cyclic triaxial tests: first, when the pore pressure becomes equal to the effective confining pressure, and, second, when the axial strain reaches 5% of the double amplitude.
Ključne besede: snail soil, cyclic triaxial test, porosity, permeability, consolidation, Young’s modulus, shear modulus, damping ratio, Poisson’s ratio, friction angle
Objavljeno: 18.05.2018; Ogledov: 581; Prenosov: 34
.pdf Celotno besedilo (479,11 KB)
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Fuzzy-sets decision-support system for geotechnical site soundings
Djemalddine M. Boumezerane, Smaïn Belkacemi, Bojan Žlender, 2011, izvirni znanstveni članek

Opis: A geotechnical site investigation is an important and complex task that is generally carried out in two steps. The first step, consisting of preliminary soundings, guides the subsequent site characterization. The number of soundings required to adequately characterize a site is set on the basis of an engineering judgement following the preliminary investigation, this is affected by the geological context, the area topography, the project type, and the knowledge of the neighbouring areas. A fuzzy-sets decision-support system, considering parameters that affect the number of soundings required to adequately characterize a site, is proposed. Parameter uncertainties and a lack of information are also considered. On the basis of the available qualitative and quantitative information, the proposed fuzzy system makes it possible to estimate, for a common project, the number of site soundings required to adequately characterize the site. The cases presented show that a Fuzzy Inference System can be used as a systematic decision-support tool for engineers dealing with site characterizations.
Ključne besede: geotechnical investigation, soundings number, fuzzy sets, fuzzy inference, uncertainties
Objavljeno: 13.06.2018; Ogledov: 114; Prenosov: 27
.pdf Celotno besedilo (544,70 KB)
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Modeling of a geocell-reinforced pavement
Samo Peter Medved, Bojan Žlender, Stanislav Lenart, Primož Jelušič, 2016, izvirni znanstveni članek

Opis: This article details how the serviceability of a flexural pavement structure is improved by incorporating the Cellular Confinement System (geocells). For this purpose, two different pavement structures, with and without embedded geocells, were manufactured in a laboratory and an accelerated traffic type of loading was applied. The vertical and horizontal cyclic loads were applied simultaneously to simulate the effect of principal stress rotation. A comparative study between the conventional flexible pavement and the geocell-reinforced flexible pavement is presented. Additionally, numerical models of the laboratory tests were built and the results were compared. The simulation of the experimental tests using the Traffic Load Simulator (TLS) are carried out using the FEM and advanced models that describe the permanent strain behavior of the unbound granular material. The development of permanent deformation within the pavement structure, with and without the geocells, is also presented through the numerical model, which was verified by the experimental results.
Ključne besede: flexible pavement, reinforcement, geocell, traffic load simulator, permanent deformation, numerical modeling
Objavljeno: 18.06.2018; Ogledov: 137; Prenosov: 19
.pdf Celotno besedilo (1,39 MB)
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Davor Burkelc, 2011, diplomsko delo

Opis: Namen diplomskega dela je statična in dinamična analiza stebra vetrne elektrarne. Gre za energetski objekt moči 1 MW. Glavna nosilna konstrukcija je stožec spremenljivega prereza iz konstantne debeline pločevine. Višina stebra znaša 65 m. Steber je sidran na temelju s sidrnimi vijaki M 30. Na vrhu stebra je pritrjeno ohišje, v katerem so pomembni elementi za proizvajanje električne energije. Premer rotorja znaša 64 m in je sestavljen iz treh lopatic dolžine 31,05 m. Skupna višina tako znaša 98,25 m, merjeno od začetka stebra do vrha lopatice. Za glavno nosilno konstrukcijo smo uporabili jeklo kakovosti S 355. Vetrna elektrarna je temeljena na točkovnem temelju okrogle oblike. Temelj ima premer 15 metrov in je zgrajen iz armiranega betona kakovosti C20/25 in armature S 500. V uvodu sta opisana zgodovina in delitev vetrnih elektrarn. Predstavljene in izračunane so tudi obtežbe vetra, ledu in potresa ter dimenzioniranje objekta po pravilih EUROCODE in standardih ISO.
Ključne besede: gradbeništvo, jeklene konstrukcije, vetrna elektrarna, analiza konstrukcij.
Objavljeno: 07.06.2011; Ogledov: 2320; Prenosov: 283
.pdf Celotno besedilo (7,04 MB)

Rebeka Križaj, 2015, magistrsko delo

Opis: V magistrskem delu je predstavljeno preddimenzioniranje glavnega dela jeklenega paličnega železniškega mostu Kelaniya Bridge na Šrilanki z vijačenimi spoji po standardu Evrokod. Most, skupne dolžine 262,90 m, je sestavljen iz treh delov: iz jeklenega pristopnega mostu, glavnega mostu in armiranobetonskega pristopnega mostu. Glavni del mostu je sestavljen iz treh enakih podsistemov, razpon ene jeklene palične mostne konstrukcije meri 51,70 m. Poudarek leži na dimenzioniranju na utrujanje, zato so v tekstu podane tudi osnove utrujanja jekla. Dimenzioniranje mostu na utrujanje je izvedeno na podlagi dokaza s faktorji ekvivalentnih poškodb z obtežnim modelom LM71. Most je prav tako dimenzioniran na mejno stanje nosilnosti, kjer sta med drugim prikazana dokaz stabilnosti po teoriji drugega reda z upoštevanjem globalnih in lokalnih nepopolnosti ter dokaz s pomočjo metode nadomestnega tlačnega elementa. Na mejno stanje nosilnosti je dimenzionirana tudi spodnja konstrukcija z globokim temeljenjem. Ob koncu je prikazana primerjava med izkoriščenostmi prerezov konstrukcije po mejnem stanju nosilnosti in utrujanja.
Ključne besede: gradbeništvo, jeklene konstrukcije, železniški most, analiza, dimenzioniranje, utrujanje
Objavljeno: 04.05.2015; Ogledov: 791; Prenosov: 212
.pdf Celotno besedilo (8,96 MB)

Igor Pinter, 2015, diplomsko delo

Opis: Močne in izdatne padavine lahko povzročijo hiter porast pretokov vodotokov. Do poplav lahko pride kjerkoli. Protipoplavno varstvo ni nikoli dokončno in zanesljivo, saj so poplave naravni pojav, ki jih je nemogoče v celoti preprečiti. Doseči je mogoče le določeno stopnjo zaščite pred poplavami. Učinkovita protipoplavna zaščita z visokovodnimi nasipi predstavlja konstrukcijske rešitve v danih okoliščinah, optimizirane glede na lokalne tehnološke zmožnosti in ekonomsko situacijo v času gradnje nasipov. Glavni vidiki pri dokazovanju protipoplavne zaščite z izvedbo visokovodnega nasipa so geomehanske analize, usmerjene na dokazovanje ustreznosti vgrajenih materialov v telo nasipa ter ocena precejnih in strižnih lastnosti vgrajenega materiala. V diplomski nalogi je prikazana modifikacija osnovnega koncepta izgradnje visokovodnega nasipa, ki je analizirana z mehanskega in ekonomskega vidika s ciljem določitve optimalne protipoplavne zaščite poplavno ogroženega območja med naseljema Vurberk in Zgornji Duplek.
Ključne besede: visokovodni nasip, napetostna stanja, prepustnost, deformacije, strižna odpornost, količnik varnosti, tehnično opazovanje, stroškovna učinkovitost
Objavljeno: 04.01.2016; Ogledov: 881; Prenosov: 196
.pdf Celotno besedilo (11,64 MB)

Osnutek katastra plazov občine Litija : diplomsko delo visokošolskega študija
Jože Poglajen, 1998, diplomsko delo

Ključne besede: kataster plazov, geologija, sanacija plazišča
Objavljeno: 26.07.2007; Ogledov: 1741; Prenosov: 0

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