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1.
Effect of particle roundness and morphology on the shear failure mechanism of granular soil under strip footing
Babak Karimi Ghalehjough, Suat Akbulut, Semet Çelik, 2018, original scientific article

Abstract: This study investigates the effect of particles roundness and morphology on the shear failure mechanism of soil. A strip footing was modeled under laboratory conditions. Calcareous soil was tested with three roundness classes: angular, rounded and well-rounded shapes with sizes of 0.30 mm to 4.75 mm. These were divided into six different groups at three relative densities of 30%, 50% and 70%. A series of photographs was taken during the tests and analyzed using the particle image velocimetry (PIV) method to understand the soil-deformation mechanism. The results showed that increasing the sample sizes increased the affected area of the soil. At the same time, increasing the relative density caused a punching failure mechanism that went towards the general failure. The shear failure mechanism of the soil changed from general toward punching shear failure with increasing particle roundness. This effect was larger with the smaller materials. Underneath the affected layers of soil, the angular samples were deeper than the rounded and well-rounded samples. The affected depth in the angular soil was approximately 1.5B in the smallest size group. This was more than 3B and near 4B in the largest size group. Both the sides and the underlying soil layers should be considered on angular soils. The area under the footing becomes more important than the side parts after increasing the roundness of the particles.
Keywords: particle roundness, morphology of particles, shear failure mechanism, strip footing, PIV method, ultimate bearing capacity
Published in DKUM: 11.10.2018; Views: 996; Downloads: 360
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2.
A fundamental study of the performance of X-section cast-in-place concrete single piles
Yu Wang, Yaru Lv, Dongdong Zhang, Jieying Zhou, 2016, original scientific article

Abstract: X-section cast-in-place concrete (XCC) piles are used because they have a higher bearing capacity than circularsection cast-in-place concrete (CCC) piles of the same cross-sectional area. Although the bearing capacity of XCC piles has been studied, the performance of XCC single piles, especially for the stress-transfer mechanism dependent on the geometrical effects, is still not fully understood. This paper reports two comparative field static load tests on an XCC and a CCC single pile of the same cross-sectional area. In addition, corresponding threedimensional numerical back-analyses are performed to provide a fundamental understanding. The measured and computed results reveal that the XCC single pile has an approximately 25% higher ultimate bearing capacity than the CCC single pile. This is because the XCC single pile has an approximately 20% larger total side resistance, which is caused by a 60% larger pile perimeter and a slightly smaller unit side resistance. Lateral soil arching effects are developed, causing a non-uniform effective normal stress and a shear stress across the circumference of the XCC single pile. It is suggested that XCC single piles have a higher efficiency in terms of material saving compared with CCC single piles.
Keywords: X-section cast-in-place concrete pile, field static load test, three-dimensional numerical back-analysis, stresstransfer mechanism, side resistance, soil arching
Published in DKUM: 15.06.2018; Views: 919; Downloads: 36
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3.
Corrosion mechanisms for cemented soils in three different sulfate solutions
Pengju Han, Chao Ren, Xiaohong Bai, Frank Chen, 2015, original scientific article

Abstract: In order to simulate and study the corrosion effects on the compressive strength of cemented soils that could be exposed in a polluted environment, a series of tests were conducted on cemented soil blocks cured with different concentrations of H2SO4, MgSO4, and Na2SO4 solutions. The test results show that the corrosion degree generally increases with the corrosion time and the solution concentration, while the compressive strength decreases with the increasing corrosion degree. The corrosion degree is highest for the Na2SO4 solution, followed by the MgSO4 and H2SO4 solutions. Namely, when the SO4 2- ion exists in a solution, the corrosion degree for the positive ions follows this descending order: Na+, Mg2+, and H+. X-ray diffraction (XRD) phase analyses were performed for the cemented soil samples after corrosion and ionic concentrations. The results show that the compressive strength decreases with an increase of the Mg2+ concentration in the MgSO4 solution and the Na+ concentration in the Na2SO4 solution. At the same time, the strength increases with an increase of the pH value of the H2SO4 solution. Based on the chemical analysis results, the corrosion of H2SO4 or MgSO4 solutions on cemented soils is deemed as a composite action involving the combined resolving and crystallizing corrosion processes. Furthermore, the corrosion of the Na2SO4 solution of cemented soil is a composite action consisting of dissolving and crystallizing.
Keywords: cemented soil, compressive strength, corrosion mechanism, sulfate, pollution, solution
Published in DKUM: 15.06.2018; Views: 1000; Downloads: 52
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4.
Load transfer and stress in a piled gravity retaining wall
Qun Chen, Li Wan, Changrong He, Zihui Lai, 2010, original scientific article

Abstract: The piled retaining wall is a new type of railway retaining structure in China. In the current design, the retaining wall, the beam and the piles are assumed to be independent components. Both the mutual action of the retaining wall, the piles and beam, and the influence of the soil or rock foundation on the structure are not fully considered, so that there are some limitations in the current design method. In this paper, using field observations and a three-dimensional finite-element analysis, the lateral earth pressure on the wall back, the stress distributions and the forces of the reinforcements in the beam and the pile were studied. The simulation results were in good agreement with the field observation data. These results revealed that the tensile stresses were very small and that these stresses were positive in most zones in the beam and the pile. It can also be observed that the tensile stresses or forces in the beam and pile obtained in this study were much smaller than those obtained using the current design method. This clarified the fact that the current design method used for the beam and the pile was very conservative and that it should be optimized to consider the effect of the foundation on the whole structure and the interactions among the different components.
Keywords: piled gravity retaining wall, field observation, finite-element analysis, stress, load transfer mechanism
Published in DKUM: 11.06.2018; Views: 601; Downloads: 56
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5.
Determination of passive earth pressure using three-dimensional failure mechanism
Helena Vrecl-Kojc, Stanislav Škrabl, 2007, original scientific article

Abstract: This paper presents a modified three-dimensional (3D) failure mechanism for determining the 3D passive earth pressure coefficient using the upper bound theorem within the framework of the limit analysis theory. The translational kinematically admissible failure mechanism generalized with a depth of h = 1.0 is considered in the analysis. The mechanism geometry presents a volume of rigid blocks composed of the central body and two lateral rigid bodies, which are connected by a common velocity field. The front surface of the central body interacts with the retaining wall, while the upper surface can be loaded by surcharge loading. The lateral body segments represent four- and three-sided polygons in the cross section of the central body; therefore, they define the polygonal failure surface of the central part. At the outer side, each segment of the lateral body is bounded by infinitesimally spaced rigid half-cones that describe the envelope of a family of half-cones. The numerical results of 3D passive earth pressure limit values are presented by non-dimensional coefficients of passive earth pressure influenced by the soil weight Kpg and a coefficient of passive earth pressure influenced by the surcharge Kpq. This research was intended to improve the lowest values obtained until now using the limit analysis theory. The results are presentedin a graphical form depending on the geometrical parameters and soil properties. A brief description of two world-recognized failure mechanisms based on the limit analysis approach, and the comparison of three failure mechanism results are also presented.
Keywords: soil mechanics, passive earth pressure, upper bound theorem, optimization, three-dimensional failure mechanism
Published in DKUM: 18.05.2018; Views: 690; Downloads: 41
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Diagonal cumulation of origin as the EU's institutional incentive mechanism for promoting international trade and business
Milan Jurše, Klavdij Logožar, Romana Korez-Vide, 2010, original scientific article

Abstract: In this paper we explore the effects of a diagonal cumulation of origin as the EU's Common Commercial Policy (CCP) incentive mechanism that affects the intraregional trade and transaction cost structure of firms engaged in cross-border business operation. The research explores how firms should frame their cross-border physical flows of goods and the configuration of their value-adding processes for taking advantage of diagonal cumulation of origin. The empirical analysis is based on an in-depth case study of effects of the 'SAP+ diagonal cumulation of origin' on changes in the transaction cost structure of a selected Slovenian firm operating within the household-appliance sector in one of the Western Balkan Countries. Based on eligibility of local subsidiary for using origin of goods in its import/exporttransactions the cost calculations were made for its products and then three different business scenarios were developed for showing the effects of the mechanism on transaction cost changes of a firm. The paper concludes that, at the conceptual level, the mechanism of diagonal cumulation of origin may serve as an effective institutional cross-border trade-promoting tool.
Keywords: international business, institutional incentive mechanism, diagonal cumulation of origin, European Union, EU, transaction costs, Western Balkan Countries
Published in DKUM: 17.07.2017; Views: 686; Downloads: 153
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9.
Manipulability of a haptic mechanism within the cylindrical space of an MR scanner
Matej Rajh, Srečko Glodež, Jože Flašker, Karl Gotlih, 2012, original scientific article

Abstract: The aim of this paper is to present developed 3 DOF haptic mechanism and 3D visualization method for analysis of mechanism manipulability problems within limited space. Improvement in mechanism manipulability within cylindrical space is crucial for devices, which operate in MR tunnel. This solution enables the plotting of quantitative 3D representation for each point in the mechanism's workspace, using selected resolution which can be determined in advance. The cross-section between the limited space and the whole arbitrary workspace shows the ability for movement execution.
Keywords: gibljivost, Jacobijeva matrika, delovni prostor, haptični mehanizem, MR-združljivost, omejen prostor, manipulability, Jacobian matrix, workspace, haptic mechanism, MR compatibility, limited workspace
Published in DKUM: 10.07.2015; Views: 898; Downloads: 82
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10.
Design of independent suspension mechanism for a terrain vehicle with four wheels drive and four wheels steeering
Shpetim Lajqi, Stanislav Pehan, Naser Lajqi, Afrim Gjelaj, Jože Pšeničnik, Sašo Emin, 2013, original scientific article

Abstract: In this paper a terrain vehicle with four wheels drive and four wheels steer intended to use for recreational purpose is presented. The main purpose is to design the suspension mechanism that fulfills requirements about stability, safety and maneuverability. Nowadays, as well as in the past, the development of the suspension systems of the vehicle has shown greater interest by designers and manufacturers of the vehicles. Research is focused to do a comprehensive study of different available independent suspension system (MacPherson, double wishbone, multi-link) and hence forth develop a methodology to design the suspension system for a terrain vehicle. Few chosen suspension systems are analyzed into the very details in order to find out the optimal design of it. During development process of the suspension system should be considered design constraints and requirements provided in the checklist. Afterwards the simulation results for kinematics analyses of suspension mechanism are performed in Working Model 2D and MATLAB environments. Achieved results are discussed in detail in order to find the best solution that will fulfill pretentious requirement from developed suspension system. All these investigations and reviews related to the suspension system will be exploited in order to obtain the optimal suspension geometry to equip a terrain vehicle, with such system.
Keywords: terrain vehicle, design, suspension mechanism, suspension geometry
Published in DKUM: 10.07.2015; Views: 1134; Downloads: 61
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