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Numerical simulation of intact rock behaviour via the continuum and Voronoi tesselletion models : a sensitivity analysis
Teja Fabjan, Diego Mas Ivars, Vladimir Vukadin, 2015, izvirni znanstveni članek

Opis: The numerical simulation of intact rock microstructure and its influence on macro-scale behaviour has received a lot of attention in the research community in recent years. Generating a grain-like structure with polygonal area contacts is one of the avenues explored for describing the rock’s microstructure. A Voronoi tessellation implemented in the Universal Distinct-Element Code (UDEC) is used to generate models with a polygonal microstructure that represent intact rock. The mechanical behaviour of the Voronoi polygons is defined by micro-properties, which cannot be measured directly in the laboratory. A numerical calibration procedure is needed to produce the macroscopic response of a model that corresponds to the material behaviour measured during a laboratory experiment. In this research, Brazilian, direct tensile, uniaxial compressive and biaxial test models are constructed to simulate the intact rock behaviour under a standard laboratory stress. An extensive series of parametric sensitivity analyses are executed in order to understand the influence of the input micro-properties on every model test behaviour and predict the relation between the micro-properties and the model’s macro response. The results can be treated as general guidelines for a complete and efficient intact rock calibration procedure. In parallel, a continuum-based model using the Mohr-Coulomb constitutive relationship is running as a benchmark. It has been shown that the Voronoi-based models through their microstructure approach better reproduce the Brazilian to direct tensile strength ratio, and show a better representation of the dilation, crack pattern and post-peak behaviour in comparison to continuum models.
Ključne besede: distinct-element method, parametric sensitivity analysis, intact rock, Voronoi tessellation, micromechanical properties, standard laboratory test
Objavljeno v DKUM: 15.06.2018; Ogledov: 1297; Prenosov: 88
.pdf Celotno besedilo (1,57 MB)
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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 v DKUM: 14.06.2018; Ogledov: 946; Prenosov: 69
.pdf Celotno besedilo (700,29 KB)
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Influence of $K_0$ on the creep properties of marl
Zvonko Tomanović, 2009, izvirni znanstveni članek

Opis: The influence of the stress state on the deformation response of a rock mass has been experimentally examined on uniaxial, bi-axial and three-axial specimens of marl at short loading and in creep tests for periods of 3 to 180 days. The lateral (horizontal) pressure significantly changes the deformation behaviour of both the initial deformations induced by the stress change and creep deformations. The influence of lateral pressure on the vertical deformation can be well approximated by a linear function.
Ključne besede: creep, soft rock, marl, rheological model, lateral stress, laboratory testing
Objavljeno v DKUM: 06.06.2018; Ogledov: 779; Prenosov: 55
.pdf Celotno besedilo (628,89 KB)
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Vpliv jazza na popularno glasbo
Marko Žaler, 2018, magistrsko delo

Opis: V magistrskem delu sta bili predstavljeni glasbeni zvrsti jazz in popularna glasba od nastanka do razvrstitve po obdobjih in delitve po smereh, zakaj so nastale ter njihove značilnosti. Namen je bil tudi utemeljitev hipotez in čim bolj smiselni opis vpliva jazza na popularno glasbo in povezav med njima, kar sem predstavil tudi z notnim gradivom in analizo skladb. Glede na dejstvo, da je glasbenih primerov in izvajalcev, ki bi jih v povezavi z obravnavanima zvrstema lahko opisal, ogromno, analiza mnogih pa bi močno presegla okvir zadane naloge, sem se odločil, da se bom posvetil zasedbama, ki me najbolj zanimata, torej The Beatles z njihovim producentom Georgom Martinom ter Michael Jackson z producentom Quincyjem Jonesom.
Ključne besede: Jazz, popularna glasba, rock'n roll, blues, pop, rock, The Beatles, Michael Jackson, Quincy Jones.
Objavljeno v DKUM: 05.06.2018; Ogledov: 1301; Prenosov: 162
.pdf Celotno besedilo (3,85 MB)

A 3D nonlinear dynamic analysis of a rock-fill dam based on IZIIS software
Violeta Mircevska, Vladimir Bickovski, Mihail Garevski, 2007, izvirni znanstveni članek

Opis: This paper treats the 3D nonlinear dynamic behavior of a rock-fill dam based on the Mohr-Coulomb failure criterion. The dam is situated in a steep, narrow, “V-shaped” rigid canyon. The concept of a massless rock foundation is treated, for which a certain part of the rock is included in the model. The dam-rock interface was modeled by contact elements, which allowed certain relative displacements between the two media of different stiffnesses. The generation of the 3D mathematical model was related to the topology of the terrain, and the nonlinear dynamic response was based on the "step-by-step" linear-acceleration direct-integration method, making use of the Wilson-θ method. The convergence process was in accordance with the Newton-Raphson method. First, the initial static effective stresses existing in the conditions of the established stationary filtration through the clayey core were defined. The analysis was based on an original FE program for the static and dynamic analyses of rock-fill dams, as well as a FE program for the solution of the stationary filtration process through the clayey core. The dynamic response of the 3D model of the dam was defined for the effect of harmonic excitations. Dynamic analyses in the linear and nonlinear domains were performed for the purpose of comparing the results. The time histories of the linear and nonlinear responses were defined for selected sections and nodes of the model, the tension cut-off zones, the plastic deformations, and the stress-shear strain relationships. The coefficient against the sliding of the potential sliding surfaces was also defined. It can be concluded that 3D analyses as well as a nonlinear material treatment of the soils built in the dam are imperative for a proper assessment of the stability of rock-fill dams situated in narrow canyons.
Ključne besede: automatic generation of 3D model, rock-fill dam, nonlinear dynamic analysis, elastic perfectly plastic criterion, tension cutoff, cracking zones, plastic deformations, stability
Objavljeno v DKUM: 18.05.2018; Ogledov: 1303; Prenosov: 82
.pdf Celotno besedilo (923,69 KB)
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New trends in rock mass characterisation for designing geotechnical structures
Drago Ocepek, 2005, izvirni znanstveni članek

Opis: The investigation on designing supporting measures for geotechnical structures consists of the proper selection of the input data for the stress – strain analysis of the excavation process and the selection of retaining measures. In the preliminary phase of investigation the area must be geologically mapped in detail, and discontinuities precisely measured, boreholes and their “in situ” tests listed and samples for laboratory examinations taken. The new method allows rock mass classification for different rock quality, from soft rocks to mixed rock masses, as well as determination of the geological strength index GSI. The limits for using the suggested method are persistent discontinuities in rock mass which lead to translation or rotation failure mechanisms, either in a single plane or as a wedge. In all cases where discontinuities play a significant role, the rock mass structure must be considered and kinematical analyses performed. In other circumstances, a rock may be uniform and reasonably isotropic due to the geometry of discontinuities and their mutual intersections. The value range of GSI is first determined in the beginning of investigation and later in the excavation phase by considering the disturbance factor D, which expresses disturbances caused by excavation methods and rock mass relaxation. The strength and deformability parameters of rocks of different quality are determined by the generalized Hoek-Brown failure criterion and applied to shallow and deep tunnels or slopes. Before the start of excavations work and after establishing the retaining measures, the analysis results are checked by monitoring. New methods include the determination of post peak strength parameters of rock mass after relaxation, and routine measurements. The newest measurement system however allows direct readings of displacements of the rock mass in both the elastic and post-peak states. With back analyses we determine the softening behavior of the rock mass and a possible need for increasing retaining measures. Such a design method enables the optimization of retaining measures and the reduction of investment costs.
Ključne besede: geological strength index – GSI, simulation of a triaxial large scale »in situ« test, numerical modeling, retaining measures, rock reinforcement, monitoring, back analyses, strain softening, rock mass relaxation
Objavljeno v DKUM: 16.05.2018; Ogledov: 1042; Prenosov: 56
.pdf Celotno besedilo (1,05 MB)
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Biodiversity in models of cyclic dominance is preserved by heterogeneity in site-specific invasion rates
Attila Szolnoki, Matjaž Perc, 2016, izvirni znanstveni članek

Opis: Global, population-wide oscillations in models of cyclic dominance may result in the collapse of biodiversity due to the accidental extinction of one species in the loop. Previous research has shown that such oscillations can emerge if the interaction network has small-world properties, and more generally, because of long-range interactions among individuals or because of mobility. But although these features are all common in nature, global oscillations are rarely observed in actual biological systems. This begets the question what is the missing ingredient that would prevent local oscillations to synchronize across the population to form global oscillations. Here we show that, although heterogeneous species-specific invasion rates fail to have a noticeable impact on species coexistence, randomness in site-specific invasion rates successfully hinders the emergence of global oscillations and thus preserves biodiversity. Our model takes into account that the environment is often not uniform but rather spatially heterogeneous, which may influence the success of microscopic dynamics locally. This prevents the synchronization of locally emerging oscillations, and ultimately results in a phenomenon where one type of randomness is used to mitigate the adverse effects of other types of randomness in the system.
Ključne besede: biodiversity, cyclic dominance, rock-paper-scissors, physics of social systems
Objavljeno v DKUM: 23.06.2017; Ogledov: 889; Prenosov: 313
.pdf Celotno besedilo (419,58 KB)
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Miha Nemanič, 2015, diplomsko delo

Opis: Popularna glasba predstavlja kompleksno prostočasno aktivnost otrok in mladostnikov. Ravno zaradi tega jo je smiselno vključevati v šolske programe, kajti če izhajamo iz vsebin, ki so med učenci priljubljene, lahko širimo njihovo polje zanimanja tudi na druga področja. Namen diplomske naloge je bil raziskati, kateri dejavniki vplivajo na vključevanje učencev v šolo rock glasbe, ki poteka na osnovni šoli Vižmarje Brod, ali so načini poučevanja motivacijsko spodbudni, katere glasbene zvrsti spoznavajo učenci ter kakšno je njihovo počutje med nastopi. V teoretičnem delu je opisan razvoj rocka, odnos mladih do te glasbe, predstavljena je problematika vključevanja popularne glasbe v osnovnošolske programe ter opisano je delovanje šole rocka. V empiričnem delu smo uporabili deskriptivno in kavzalno neeksperimentalno metodo pedagoškega raziskovanja. V raziskavi sta sodelovala 102 učenca. Podatke smo pridobili z anketnim vprašalnikom in jih statistično obdelali s programskim orodjem SPSS. Raziskava je pokazala, da ne obstaja povezava med željo po igranju glasbila in dejavniki, ki so vplivali na izbiro glasbila. Ugotovljeno je bilo, da načini poučevanja na učence delujejo motivacijsko spodbudno, da spoznavajo poleg rocka tudi druge glasbene zvrsti, da so med nastopanjem v sestavih bolj samozavestni in imajo manjšo tremo kot pri solističnem nastopanju ter da po nastopih dobijo povratne informacije. Glede na ugotovitve raziskave lahko trdimo, da je program šole rocka zasnovan na način, ki pozitivno vpliva na učno motivacijo, raven samozavesti in socialni razvoj učencev.
Ključne besede: popularna glasba, šola rock glasbe, neformalno poučevanje, motivacija, samozavest, trema
Objavljeno v DKUM: 30.03.2015; Ogledov: 1953; Prenosov: 170
.pdf Celotno besedilo (3,94 MB)

Simon Alatič, 2014, diplomsko delo

Opis: Na podlagi sistematične analize izsledkov iskanja virov in doslej opravljenih raziskav skuša pričujoče diplomsko delo predstaviti simfonični rock in njegovo prepoznavnost na slovenskih tleh. Metodološko je diplomsko delo zasnovano na načelu iskanja arhivskih virov o zgodovini in razvoju simfoničnega rocka ter primerjave arhivskih virov in doslej opravljenih raziskav o simfoničnem rocku. V osrednjem delu diplomskega dela predstavi avtor glasbene skupine, ki so najbolj vplivale na razvoj simfoničnega rocka. Prav tako analizira lastno avtorsko skladbo z naslovom Oblivion, ki je bila ustvarjena v sklopu tega diplomskega dela. V sklepu je povzetek obravnavane snovi.
Objavljeno v DKUM: 28.03.2014; Ogledov: 1016; Prenosov: 95
.pdf Celotno besedilo (11,91 MB)

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