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71.
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: 14.06.2018; Ogledov: 8; Prenosov: 0
.pdf Celotno besedilo (700,29 KB)

72.
Editorial
Bojana Dolinar, 2014, predgovor, spremna beseda

Ključne besede: editorials, scientific journals, geomechanics, geotechnical engineering
Objavljeno: 14.06.2018; Ogledov: 6; Prenosov: 0
.pdf Celotno besedilo (29,62 KB)
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73.
Investigations to establish the influence of the thermal energy field on soil properties
Srinivas Kadali, Susha Lekshmi, Susmita Sharma, D. N. Singh, 2013, izvirni znanstveni članek

Opis: This paper describes details of a study to investigate and demonstrate the changes undergone by soil when it is exposed to elevated temperatures. Such situations are commonly encountered while designing the foundations for the furnaces, boiler units, forging units, brick kilns, rocket launching pads, buried power-supply cables, air-conditioning ducts, underground explosions, disposal of high-level radioactive and industrial toxic wastes, ground modifications or soil-stabilization techniques, etc. As such, investigations to establish changes undergone by the soil when it is exposed to elevated temperatures assume some importance. With this in view, individual samples of six soils, with entirely different characteristics, were subjected to temperatures up to 300°C (sequentially in steps of 50°C) and after each step of thermal treatment, these samples were characterized for their physical, chemical and mineralogical properties. Based on a critical synthesis of the results, it has been demonstrated that elevated temperatures cause (i) a change in the color, (ii) an increase in the specific gravity, particle size and weight loss, (iii) a reduction in the specific surface area, cation-exchange capacity and zeta-potential, and (iv) a structural transformation of the soil. Though these changes would affect the engineering properties of the soil to a large extent, the scope of this paper is limited to demonstrating the alterations in physical, chemical and mineralogical changes, only, occurring in the soil when it is exposed to elevated temperatures.
Ključne besede: elevated temperatures, soil, characterization, physical characteristics, chemical characteristics, mineralogical characteristics
Objavljeno: 14.06.2018; Ogledov: 7; Prenosov: 0
.pdf Celotno besedilo (1,08 MB)

74.
Evolutionary-based prediction of ε50 for the lateral load-displacement behavior of piles in clay
Babak Ebrahimian, Aida Nazari, 2013, izvirni znanstveni članek

Opis: Analyzing piles that are subjected to lateral loads reveals that their behavior depends on the soil’s resistance at any point along the pile as a function of the pile’s deflection, known as the p-y curve. On the other hand, the deformation characteristics of soil defined as “the soil strain at 50% of maximum deviatoric stress (ε50)” have a considerable effect on the generated p-y curve. In this research, several models are proposed to predict ε50 specifically for designing the very long pile foundations of offshore oil and gas platforms in the South Pars field, Persian Gulf, Iran. Herein, ε50 is evaluated using extensive soil data, including in-situ and laboratory test results using evolutionary polynomial regression (EPR). The effects of the undrained shear strength, the normalized tip resistance of the cone penetration test, the over-burden pressure, the plasticity index and the over-consolidation ratio on ε50 are investigated in marine clays. It is demonstrated that the normalized cone tip resistance, which is an indication of the soil’s undrained shear strength, leads to more realistic ε50 values compared with the laboratory-derived undrained shear strength parameter. In addition, the application of the soil-index properties and the over-burden pressure in the models, improves their estimation quality. Furthermore, the results of full-scale lateral pile load tests at different sites are used in order to validate the performance of the proposed models when it comes to predicting the behavior of the lateral piles.
Ključne besede: p-y curve, laterally loaded pile, piezocone penetration test, PCPT, marine clay, evolutionary polynomial regression, EPR, South Pars field
Objavljeno: 14.06.2018; Ogledov: 8; Prenosov: 0
.pdf Celotno besedilo (676,68 KB)

75.
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: 10; Prenosov: 0
.pdf Celotno besedilo (360,65 KB)

76.
On the application of a mixed finite-element approach to beam-soil interaction
Vedran Jagodnik, Gordan Jelenić, Željko Arbanas, 2013, izvirni znanstveni članek

Opis: In this paper the deformation of a Bernoulli beam resting on Winkler's soil is reviewed in terms of the mixed finite-element methodology. While the stiffness matrix of the Bernoulli beam problem utilizing the standard displacement-based approach, in which only the displacement field is interpolated, may be alternatively obtained using a mixed-type approach to the absolutely shear-stiff second-order Timoshenko beam (in which the rotation and shear-stress resultant fields are additionally interpolated), the two approaches lead to different Winkler-type soil-stiffness contributions. Furthermore, extending the mixed-type formalism to both of these elements by additionally interpolating the distributed soil-reaction field, the soil-stiffness contributions also differ. In this way four different elements are obtained, with one, two, three or four independently interpolated fields, in which the beam-stifness matrix is equal, but the soil-stiffness matrices are different. It is demonstrated that the displacement-based one-field element is the least convergent, while the mixed-type element with four interpolated fields is the most convergent.
Ključne besede: Bernoulli beam, Winkler soil, mixed finite-element method
Objavljeno: 14.06.2018; Ogledov: 5; Prenosov: 0
.pdf Celotno besedilo (413,70 KB)

77.
Atterberg limits in relation to other properties of fine-grained soils
Bojana Dolinar, Stanislav Škrabl, 2013, izvirni znanstveni članek

Opis: In soil mechanics the Atterberg limits are the most distinctive and the easiest property of fine-grained soils to measure. As they depend on the same physical factors as the other mechanical properties of soils, the values of the liquid and plastic limits would be a very convenient basis for their prediction. There are many studies concerning the use of the Atterberg limits in soil mechanics; however, their results vary considerably and are not generally applicable. This paper explains the main reasons for the different conclusions in these studies, which do not take into account the following: a) the water in fine-grained soils appears as interparticle and interaggregate pore water as well as adsorbed water onto the surfaces of clay minerals; b) the physical properties of fine-grained soils depend on the quantity of pore water only, because the adsorbed water is tightly tied on the clayʼs external and internal surfaces and thus cannot influence to them; c) the quantity of adsorbed water on the external surfaces of the clay minerals in soils depends mostly on the size and the quantity of the clay minerals, while the interlayer water quantity depends mostly on the quantity and the type of the swelling clay minerals in the soil composition and their exchangeable cations. From this it follows that for swelling and non-swelling soils, the uniform relationships between the Atterberg limits (which represent the total quantity of pore water and the adsorbed water onto the external and internal surfaces of clay minerals) and other physical properties does not exist. This paper presents some possibilities for the use of the Atterberg limits in predicting the soilʼs other properties for non-swelling and limited-swelling soils.
Ključne besede: Atterberg limits, specific surface area, undrained shear strength, compressibility, hydraulic conductivity
Objavljeno: 14.06.2018; Ogledov: 6; Prenosov: 0
.pdf Celotno besedilo (133,59 KB)

78.
Editorial
Ludvik Trauner, 2013, predgovor, spremna beseda

Ključne besede: editorials, scientific journals, geomechanics, geotechnical engineering
Objavljeno: 14.06.2018; Ogledov: 5; Prenosov: 0
.pdf Celotno besedilo (37,30 KB)
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79.
Experimental and numerical studies of T-shaped footings
Nihat Kaya, Murat Ornek, 2013, izvirni znanstveni članek

Opis: In addition to vertical axial loads, the footings of structures are often subjected to eccentric loads caused by the forces of earth pressures, earthquakes, water, wind, etc. Due to eccentric loading, the two edges settle by different amounts, causing the footing to tilt and then the pressure below the footing does not remain uniform. The T-shape is proposed as a footing shape for improving the bearing capacity of shallow footings against the action of eccentric loads. The vertical insertion of the rigid T-shaped footing, into the bearing soil, provides considerable resistance, against both of sliding and overturning, enough to regain the reduction in bearing capacity and increase in settlement. In this study, a series of experimental and numerical results from the ultimate loads and settlement of T-shaped footings are reported. A total of 48 model tests were conducted for investigating the effects of different parameters, such as the problem geometry and soil density. The problem geometry was represented by two parameters, the load eccentricity (e) and the insertion depth (H) of the T-shape into the loose and dense sand soil. After the experimental stage, the numerical analyses were carried out using a plane strain, two-dimensional, finite-element-based computer program. The behaviour of the T-shape footing on sand beds is represented by the hardening soil model. The results of the experimental and numerical studies proved that the ultimate bearing capacity of a footing under eccentric loads could be improved by inserting a vertical central cut-off rigidly connected to the footing bottom. The load settlement curves indicate that the higher load eccentricity results in a decrease in the bearing capacity of the strip footing. It was also proved that the ultimate bearing capacity values can, depending on the soil density, be improved by up to four times that of the loose sand case. This investigation is considered to have provided a useful basis for further research, leading to an increased understanding of the T-shaped footing design.
Ključne besede: model test, finite-element method, T-shaped footing, eccentric loading, sand
Objavljeno: 14.06.2018; Ogledov: 5; Prenosov: 0
.pdf Celotno besedilo (686,03 KB)

80.
Post-liquefaction volume change in micaceous sandy of Old Gediz River Delta
Ender Basari, Gurkan Ozden, 2013, izvirni znanstveni članek

Opis: Post-liquefaction settlement characteristics of micaceous sands are not well investigated topic. Currently available charts relating post-liquefaction volumetric strain to relative density were developed for clean sand. Estimation of post-liquefaction settlement of micaceous sands, therefore, may stay on the unsafe side, since there is evidence indicating that mica grains could increase volume change tendency. Influence of mica content on post-liquefaction volumetric strain of sand-mica mixtures is studied in this article. Soil samples were prepared at various relative densities. Influence of fine content that could be present in the field was also investigated on tamped natural field samples recovered from boreholes drilled in a highly populated alluvial site known as the Old Gediz River Delta of Izmir. It was found that increasing mica content at a certain relative density resulted in higher volumetric strains as compared with the data on clean sands. It is deduced that influence of mica grains on sand behavior depends on initial void ratio of sand. Effects of mica grains decrease with increasing of relative density. Simple empirical relationships were derived relating mica content and relative density to volumetric strain. It was also noticed that fine content accelerated and increased post-liquefaction volumetric strains.
Ključne besede: sand, mica, non-plastic fines, post-liquefaction volume change
Objavljeno: 14.06.2018; Ogledov: 10; Prenosov: 0
.pdf Celotno besedilo (434,60 KB)

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