Acta geotechnica Slovenica
Opis: Acta geotechnica Slovenica aims to play an important role in publishing high-quality, theoretical papers from important and emerging areas that will have a lasting impact on fundamental and practical aspects of geomechanics and geotechnical engineering.
Acta geotechnica Slovenica publishes papers from the following areas: soil and rock mechanics, engineering geology, environmental geotechnics, geosynthetic, geotechnical structures, numerical and analytical methods, computer modelling, optimization of geotechnical structures, field and laboratory testing.
The journal is published twice a year.
Ključne besede: scientific journals, geomechanics, geotechnical engineering
Objavljeno: 15.05.2018; Ogledov: 282; Prenosov: 0
Ogledov v tednu: 219
PRIPRAVA NA USTNI DEL MATURITETNEGA IZPITA IZ SLOVENŠČINENives Roter
Opis: V diplomskem delu Priprava na ustni del maturitetnega izpita iz slovenščine smo se v prvem delu posvetili teoretičnim izhodiščem. Osvetlili smo pojme matura, splošna matura, poklicna matura, priprava na splošno ter poklicno maturo, slovenščina na maturi. V drugem delu smo se usmerili v raziskavo, ki smo jo izvedli s pomočjo anketnega vprašalnika. V empiričnem delu smo tako izpostavili hipoteze, ki smo jih ob rezultatih raziskave potrdili ali ovrgli. Namen je bil predvsem predstaviti priprave na ustni del maturitetnega izpita iz slovenščine na poklicni in splošni maturi. Iskali smo razlike in podobnosti v načinu priprave, uspešnosti priprave, motiviranosti za pripravo na maturo v gimnazijah in strokovnih šolah. Pridobljene podatke smo obdelali ter jih prikazali s pomočjo tabel in grafov in jih podprli s svojim mnenjem ter z argumenti. Raziskavo smo izvedli na dveh različnih srednjih šolah. Temeljni cilj je bil izpostaviti razlike med splošno ter poklicno maturo, zato smo izbrali eno strokovno šolo ter eno gimnazijo.
Rezultati raziskave kažejo, da se pojavljajo razlike v pripravi na maturo med dijaki strokovnih šol ter dijaki gimnazij. Dijaki so za maturo ter za priprave na maturo premalo motivirani, prav tako se zdijo dijaki premalo samozavestni ter prepričani v svoje znanje in uspeh na maturi.
Ključne besede: matura, splošna matura, poklicna matura, priprava na maturo, slovenščina na maturi, gimnazija, strokovna šola.
Objavljeno: 08.10.2012; Ogledov: 2936; Prenosov: 402
Ogledov v tednu: 103
Evaluation of the plastic critical depth in seismic active lateral earth pressure problems using the stress-characteristics methodAmin Keshavarz
Opis: The plastic critical depth or the conventional tension crack depth has a considerable effect on the active lateral earth pressure in cohesive soils. In this paper the depth for c-ϕ soils has been evaluated in the seismic case using the stress-characteristics or slip-line method. The plastic critical depth was calculated on the basis of the theory of the stress-characteristics method and by considering the horizontal and vertical pseudo-static earthquake coefficients. The proposed solution considers the line of discontinuity in the stress-characteristics network. The earth slope, wall slope, cohesion and friction angle of the soil and the adhesion and the friction angle of the soil-wall interface were considered in the analysis as well. The results show that the plastic critical depths of this study are smaller than those of the other methods and are closer to the modified Mononobe-Okabe method. The effects of the wall and the backfill geometry, the mechanical properties of the soil and the pseudo-static coefficients were studied.
Ključne besede: plastic critical depth, stress characteristics, active lateral earth pressure, seismic
Objavljeno: 15.06.2018; Ogledov: 78; Prenosov: 0
Ogledov v tednu: 78
A fundamental study of the performance of X-section cast-in-place concrete single pilesYu Wang
, Yaru Lv
, Dongdong Zhang
, Jieying Zhou
Opis: 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.
Ključne besede: X-section cast-in-place concrete pile, field static load test, three-dimensional numerical back-analysis, stresstransfer mechanism, side resistance, soil arching
Objavljeno: 15.06.2018; Ogledov: 74; Prenosov: 0
Ogledov v tednu: 74
Micro-scale responses of granular materials under different confining pressures using the discrete element methodMahmud Sazzad
Opis: Biaxial compression tests were carried out on assemblies of ovals to study the micro-scale responses of granular materials under different confining pressures using the discrete element method (DEM). A total of 8450 ovals were generated in a rectangular frame without any overlap. Four dense samples were prepared from the initially generated sparse sample under different confining pressures. The simulated results yield a stress-straindilatancy behaviour similar to that observed in sands under different confining pressures. The evolution of the different microparameters and their inter-relationships are established. When the confining pressure is relatively high, the difference between the coordination number and the effective coordination number is very small; however, the difference is apparent for a low confining pressure. The microtopology of the granular assembly at several important states of shear is also reported. It is noted that the topological distribution of the granular materials is confining- pressure dependent. The normalized void-cell number is a minimum under the lowest confining pressure, whereas the same number is a maximum under the highest confining pressure. A linear relationship is observed between the normalized void-cell number and the effective coordination number, regardless of the confining pressures. The evolution of the deviatoric fabric for different confining pressures is measured and the macro-micro relationship is presented.
Ključne besede: microstructures, confining pressure, fabric, microtopology, coordination number, macro-micro relationship
Objavljeno: 15.06.2018; Ogledov: 74; Prenosov: 0
Ogledov v tednu: 74
Empirical correlation between the shear-wave velocity and the dynamic probing heavy testStjepan Strelec
, Davor Stanko
, Mario Gazdek
Opis: Varaždin is located in the north-western part of Croatia in shallow quaternary alluvial sediments of the Drava River basin. Local site effects due to the alluvial soft sediments can play a crucial role in the amplification of seismic-wave ground motions. The shear-wave velocity (VS) is one of the most important parameters for determining dynamic soil properties and ground-response analyses.
The seismic surface wave method (MASW) is the simplest and a very efficient way of measuring the shear-wave velocity in the field. The Dynamic Probing Heavy (DPH) test is suited to determining the soil strength and the soil deformation properties. However, there are a lack of correlations between the shear-wave velocity and the DPH tests (VS - NDPH) in the literature. In this paper we present empirical correlations between the shear-wave velocity VS and the soil penetration resistance NDPH with: a) raw (original) NDPH data: VS = 97.839·NDPH0.395, (R2 = 0.723); b) a groundwater correction NDPH data: VS = 92.998·NDPH0.363 (R2 = 0.815). From the measured DPH data, the shear-wave velocity (VS), the shear modulus (Go) and the Young’s modulus (Eo and Er) were estimated. Two different approaches (low vs. high strain) were compared, and the results were found to be in good agreement when the relative difference between the velocities is small and smooth.
Dynamic probing tests are good for studying a discrete point of interest in a large field area based on preliminary seismic tests. The suggested correlation VS - NDPH can be used for a rough estimation of VS from NDPH (they are site-specific, and so not applicable worldwide). In this way valuable information about dynamic soil properties can be extracted for ground-response analyses and the study of local site effects.
Ključne besede: shear-wave velocity, MASW, DPH, empirical correlations, dynamic elastic moduli, dynamic soil properties
Objavljeno: 15.06.2018; Ogledov: 73; Prenosov: 0
Ogledov v tednu: 73
Corrosion mechanisms for cemented soils in three different sulfate solutionsPengju Han
, Chao Ren
, Xiaohong Bai
, Frank Chen
Opis: 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.
Ključne besede: cemented soil, compressive strength, corrosion mechanism, sulfate, pollution, solution
Objavljeno: 15.06.2018; Ogledov: 72; Prenosov: 0
Ogledov v tednu: 72
The dry fraction of unsaturated soilsJulio César Leal Vaca
, Gustavo Gallegos Fonseca
, Eduardo Rojas González
Opis: An equation to account for the shear strength of unsaturated soils is proposed in this paper. This equation is defined as the equivalent stress, and is an extension of Murray’s equation. This approach applies to the general case of bi-modal structured soils showing a macrostructure and microstructure. The theoretical development considers the existence of a dry fraction in addition to the saturated and unsaturated fractions of the soil. These different fractions are included in a porous model, which allows an evaluation of the parameters of the equivalent stress equation. Finally, the paper includes a comparison between theoretical and experimental results. The comparison shows that the proposed equation can be used to estimate the shear strength of unsaturated soils.
Ključne besede: unsaturated soil, shear strength, equivalent stress, water retention curve
Objavljeno: 15.06.2018; Ogledov: 71; Prenosov: 0
Ogledov v tednu: 71
Reinforced piled embankment for a high-speed railway over soft soilYan Zhuang
, Xiaoyan Cui
Opis: A geosynthetic, reinforced, piled embankment is an effective and economic method to solve the problems of possible bearing failure, unacceptable settlement and slope instability for an embankment built over soft soil; this has led to its widespread use, especially for high-speed railway embankments. Some design methods have been developed to assess the performance of these reinforced structures, which are mainly based on the results from small-scale models and numerical simulations. However, the reliability of these methods needs to be validated under full-scale field tests. This paper presents a numerical and analytical study for a full-scale field test of the Fengyang high-speed railway embankment. The results were analyzed and discussed in terms of the settlement of subsoil, the stressconcentration ratio (SCR), the axial force and the frictional stress of the pile. They showed that the settlement of the subsoil, from both the finite-element method (FEM) and the analytical method, were in good agreement with the measurement, and thus was a reliable parameter to assess the performance of the piled embankment with reasonable accuracy. The SCR was overestimated by the modified Terzaghi method, with a difference of 25%, while it was underestimated by the FEM, with a difference of approximately 20%. It was also shown that the tensile force in the reinforcement could be effectively assessed using the proposed analytical method, while it was overestimated by the FEM with a difference of 44%.
Ključne besede: reinforced piled embankment, high-speed railway, numerical simulation, analytical method
Objavljeno: 15.06.2018; Ogledov: 61; Prenosov: 0
Ogledov v tednu: 61