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An unsaturated-soils approach to the bearing capacity of foundation structures
Taha Taskiran, 2017, izvirni znanstveni članek

Opis: Unsaturated soils are maintaining their importance for researchers and there is still much need to investigate the many engineering aspects of these soils. A new technique is proposed here to predict the variation of the bearing capacity of unsaturated soils with matric suction. The proposed method is an extension of conventional bearing-capacity theories and conceptually based on the logarithmic model of the shear strength of unsaturated soils, which only include one unknown, unsaturated parameter (the airentry value, AEV). The possibility of predicting the unsaturated bearing capacity of soils is shown by the saturated effective shear-strength parameters c' and Ø' and the AEV from the soil-water retention curve (SWRC). Considering the necessity of validating new methods with other researchers’ data, the proposed equation is tested using the published unsaturated experimental study by the author, in addition to some reported experimental studies on the shear strength for unsaturated soils and also a model footing loading on unsaturated sand under controlled suction conditions. The results of the study indicate that there is a good comparison between the “unsaturated bearing capacities” obtained via predicted and measured unsaturated strength parameters (ctotal , Ø) and also between the measured/ calculated bearing values of a model footing loading. Consequently, it is shown that, without needing complex unsaturated testing facilities, the proposed equation is capable of predicting the unsaturated bearing capacity for both fine-grained and sandy soils, requiring only one unsaturated parameter, which can be obtained from the SWRC or predicted using the basic soil-index properties.
Ključne besede: unsaturated soils, unsaturated bearing capacity, suction strength, foundation design
Objavljeno: 18.06.2018; Ogledov: 511; Prenosov: 40
.pdf Celotno besedilo (347,24 KB)
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Settlement of weakly cemented tufas
Nihat Dipova, Ergun Ufuk, Doyuran Vedat, 2014, izvirni znanstveni članek

Opis: Weakly cemented tufas are sand and silt size soils that are weakly bonded with thin films of carbonate cement. The void ratio is rather high and equal to approximately 1.2. Collapse occurs as a result of the destruction of the weak bonds upon loading and/or wetting. The index properties and the collapse potential (Cp) of tufa were determined in the laboratory. In the determination of the collapse-potential values the single-ring oedometer method was considered to be a suitable and simpler tool. In plotting the oedometer test results the use of a natural scale was preferred over a logarithmic scale so that the void ratio-pressure relationship is polynomial. Under loading the soil settles with the natural water content; however, saturation increases the collapse that is initially triggered by the pressure increase. The pressure level is a significant parameter in the magnitude of the collapse and therefore in the total settlement. The settlement of foundations due to a collapse of the soil structure can be estimated directly using the oedometer test results and empirically using the index properties, like the initial void ratio (e0), the difference in the fine content between the dry and the wet sieve analyses (PFAW) and the natural unit weight. A comparison of the direct and empirical approaches yielded a good agreement.
Ključne besede: Antalya, collapse potential, collapsible soils, settlement, tufa
Objavljeno: 14.06.2018; Ogledov: 340; Prenosov: 40
.pdf Celotno besedilo (454,12 KB)
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Effects of ground granulated blast-furnace slag on the index and compaction parameters of clayey soils
Osman Sivrikaya, Selman Yavascan, Emre Cecen, 2014, izvirni znanstveni članek

Opis: The use of industrial wastes in soil stabilization not only provides for the re-use of waste materials, which may cause environmental pollution, but also leads to cost benefits. In this context, the use of industrial wastes in the stabilization of fine-grained soils has become a research topic in recent years. The aim of this study is to evaluate the potential use of granulated blast-furnace slag (GBFS) in clayey soil stabilization. In this study, the GBFS obtained from the Iskenderun iron-steel plant as an industrial waste was ground into two different fineness levels, and the effects of their incorporation into low-plasticity Kolsuz clay and high-plasticity bentonite clay in various rates (5%, 10%, 20%, 30%, and 50%) on the particle weight of unit volume, the consistency limits, and the compaction parameters are investigated. Based on the experimental results, it is clear that the GBFS has a positive effect on the stabilization of both clayey soils. It was also concluded that the improvement in bentonite clay is greater than that in Kolsuz clay. Thus, GBFS seems to be a promising material for the stabilization of clayey soils.
Ključne besede: clayey soils, index properties, granulated blast-furnace slag, stabilization
Objavljeno: 14.06.2018; Ogledov: 327; Prenosov: 102
.pdf Celotno besedilo (134,83 KB)
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Prediction of the compaction parameters for coarse-grained soils with fines content by MLA and GEP
Osman Sivrikaya, Cafer Kayadelen, Emre Cecen, 2013, izvirni znanstveni članek

Opis: The determination of the compaction parameters of soils, the maximum dry unit weight (γdmax) and the optimum water content (wopt), at various compaction energy (E) levels is an important process. The aim of this study is to develop correlations in order to estimate the compaction parameters dependent on the compaction energy for coarse-grained soils with various fines contents on which limited studies exist in the literature. Genetic Expression Programming (GEP) and Multi Linear Regression (MLR) analyses are used in the derivation of the correlations for the prediction of γdmax and wopt obtained from Standard Proctor (SP) and Modified Proctor (MP) tests with the index properties of coarse-grained soils with various fines contents. To develop the models, a total of 86 data sets collected from university laboratories in Turkey and six parameters, such as gravel content (G %), sand content (S %), fines content (FC %), liquid limit (wL %) and plasticity index (IP %) of fines content and compaction energy (E Joule), are used. The performance of the models is comprehensively examined using several statistical verification tools. The results revealed that the GEP and MLR models are fairly promising approaches for the prediction of the maximum dry unit weight and the optimum water content of cohesionless soils with various fines contents at SP and MP compaction energy levels. The proposed correlations are reasonable ways to estimate the compaction parameters for the preliminary design of a project where there are financial and time limitations.
Ključne besede: coarse-grained soils, compaction, MLR, GEP
Objavljeno: 14.06.2018; Ogledov: 369; Prenosov: 39
.pdf Celotno besedilo (360,65 KB)
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Effect of plasticity and normal stress on the undrained shear modulus of clayey soils
Mehrab Jesmani, Hamed Faghihi Kashani, Mehrad Kamalzare, 2010, izvirni znanstveni članek

Opis: The shear modulus, known as Gmax, is a key parameter for predicting the static and dynamic behavior of soils. Its value decreases by increasing the shear strain. This is because of reducing the soil’s stiffness as a result of increasing the shear deformation. The increasing of the shear modulus by increasing the shear strain is affected by some of the soil properties, such as the Void ratio (e), the Over consolidated ratio (OCR), the Normal stress (σ), the Plasticity index (PI), the Water content (ω%), the Shear strain rate, the Soil structure, and the Loading history, etc. In this paper, undrained, direct shear tests were conducted to study the effect of the plasticity index (PI) and the normal stress (σ) on the shear behavior and the shear modulus of remolded clays. The results show that the normalized shear modulus at a constant strain will generally increase as the σ and PI increase, and the common empirical equations for undisturbed soils at γ = 0~0.1 might be applicable for the disturbed soils too.
Ključne besede: plasticity index, normal stress, shear modulus, disturbed clayey soils
Objavljeno: 11.06.2018; Ogledov: 449; Prenosov: 93
.pdf Celotno besedilo (703,46 KB)
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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: 617; Prenosov: 54
.pdf Celotno besedilo (679,21 KB)
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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: 660; Prenosov: 40
.pdf Celotno besedilo (486,06 KB)
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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: 654; Prenosov: 40
.pdf Celotno besedilo (586,91 KB)
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Undrained shear strength of saturated cohesive soils depending on consolidation pressure and mineralogical properties
Bojana Dolinar, 2004, izvirni znanstveni članek

Opis: The relationship between the water content and the undrained shear strength of finely grained soils can be described with a nonlinear function in which the type of soils is determined by two parameters. These parameters depend primarily on the size of clay minerals, their quantity in soil composition and the interlayer water quantity in expanding clay minerals. This article asserts that there exists also the exactly defined relationship also between the water content and consolidation pressure. In the function describing this relationship, the type of soil is determined by two parameters. They can be expressed depending on the same mineralogical properties of soils as the values of parameters in the function showing the relationship between the water content and the undrained shear strength. These findings allow us to express the ratio between undrained shear strength and consolidation pressure depending on mineralogical properties of soils.
Ključne besede: soil mechanics, properties of soils, clays, specific surface, undrained shear strenght, compressibility
Objavljeno: 15.05.2018; Ogledov: 656; Prenosov: 68
.pdf Celotno besedilo (103,26 KB)
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Contents and methods of soil geography in Slovenia
Ana Vovk Korže, 2002, pregledni znanstveni članek

Ključne besede: pedogeography, soils, Slovenia, ecology, environmental programmes
Objavljeno: 07.06.2012; Ogledov: 1041; Prenosov: 20
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