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1.
Development of a conceptual material model for structured materials - S_BRICK
Vladimir Vukadin, Jakob Likar, Vojkan Jovičić, 2005, izvirni znanstveni članek

Opis: Materials known in literature as Soft Rocks & Hard Soils such as claystones, siltstones, flysh, hard soils, marls, etc. received a lot of attention in research community in recent years. It was demonstrated that some of these materials can be described through general theoretical framework (Cotecchia & Chandler [1]), which takes into account the structure as an intrinsic material property that is present in all natural geological materials. The influence of the structure is manifested as an increase in strength and stiffness in a material. Based on a laboratory results and existent theoretical frameworks, a further step was taken with the development of a conceptual constitutive model for structured materials. A model formulated in strain space named BRICK (Simpson [2]) was chosen as a base model and was further developed with the inclusion of structure and destructuring. The new model was named S_BRICK and was tested on a conceptual level where the results of numerical tests on structured and structure less (reconstituted) materials at different stress paths were compared. The results showed that S_BRICK was able to capture stress-strain behavior typical for structured material and could be potentially used for the modeling of Soft Rocks and Hard Soils.
Ključne besede: geomechanics, soft rocks, hard soils, constitutive material models, structure, destructuring, numerical modeling
Objavljeno: 15.05.2018; Ogledov: 100; Prenosov: 5
.pdf Celotno besedilo (586,91 KB)

2.
Modeling of the stress-strain behavior in hard soils and soft rocks
Vladimir Vukadin, 2007, izvirni znanstveni članek

Opis: The paper begins with a definition of hard soils and soft rocks (HSSR); this is followed by a short overview of the typical stress-strain behavior of HSSR. It is shown that in spite of the differences in the origin, type and strength of materials, similar stress-strain behaviors can be observed for different materials, ranging from soils to rocks. Based on this observed similarity a theoretical framework can be postulated, with which an appropriate constitutive model for HSSR can be formulated. This model includes the concepts of structure and destructurization as intrinsic material properties. A model named S_BRICK that takes into account the structure and destructurization has been developed and a comparison of this model’s predictions with laboratory results is presented.
Ključne besede: geomechanics, soft rocks, hard soils, stress-strain behaviour, constitutive modeling, structure, destructurization, numerical modeling
Objavljeno: 18.05.2018; Ogledov: 121; Prenosov: 5
.pdf Celotno besedilo (679,21 KB)

3.
Development and analysis of 3D geological/geomechanical models for pumped hydroelectric power plant Kozjak
Vladimir Vukadin, 2009, izvirni znanstveni članek

Opis: In order to specify the geological and geotechnical conditions for the construction of the Kozjak pumpedstorage hydroelectric power plant (HPP), the site area has undergone considerable geological, geophysical and geomechanical investigations. Due to the complexity of the geotechnical constructions and the size of the investigated site a novel approach was proposed, where the results of the investigation were used to develop 3D geological/ geomechanical models. The models were created with the integration of all the available results and data into typical geomechanical units that were subsequently given spatial dimensions. Through an analysis of the models the relationships between the different units were better understood and the critical areas were quickly identified and verified. In this paper the models for the accumulation reservoir and the engine room are presented. The overview of the executed investigations and the results are given together with a discussion on the scope and the number of executed investigations from the standpoint of the 3D geological/geomechanical model’s creation.
Ključne besede: geological investigations, geomechanical investigations, 3D geological-geomechanical models, HPP Kozjak
Objavljeno: 06.06.2018; Ogledov: 10; Prenosov: 3
.pdf Celotno besedilo (362,83 KB)

4.
Numerical simulation of intact rock behaviour via the continuum and Voronoi tesselletion models
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: 15.06.2018; Ogledov: 21; Prenosov: 2
.pdf Celotno besedilo (1,57 MB)

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