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2. Atterberg limits in relation to other properties of fine-grained soilsBojana Dolinar, Stanislav Škrabl, 2013, original scientific article Abstract: 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.
Keywords: Atterberg limits, specific surface area, undrained shear strength, compressibility, hydraulic conductivity
Published in DKUM: 14.06.2018; Views: 1401; Downloads: 95
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3. The limit values and the distribution of three-dimensional passive earth pressuresStanislav Škrabl, 2008, original scientific article Abstract: This paper presents a novel approach to the determination of the critical distribution and limit values of three-dimensional passive soil pressures acting on flexible walls following the upper-bound method within the framework of the limit-analysis theory. The method of limit analysis with a set of three-dimensional kinematically admissible hyperbolic translational failure mechanisms is used to determine the critical distribution of the passive pressures along the retaining structurećs height. The intensity of thepassive pressures is gradually determined with the mentioned translational failure mechanisms in the top-down direction. Thus, the critical distribution,the trust point and the resultant of the passive pressures that can be activated at the limit state for the chosen kinematic model are obtained. The results of the analyses show that the total sum of passive pressures, considering the critical distribution, is lower than the comparable values published in the literature. Furthermore, the trust point of the passive pressure resultant is independent of the friction between the retaining structures and the soil.
Keywords: limit analysis, earth pressure, passive pressure, failure surface, soil-structure interaction
Published in DKUM: 05.06.2018; Views: 1160; Downloads: 168
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4. Determination of passive earth pressure using three-dimensional failure mechanismHelena 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: 1324; Downloads: 74
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5. Interactional approach of cantilever pile walls analysisStanislav Škrabl, 2006, original scientific article Abstract: This paper proposes a new method for the geomechanical analysis and design of cantilever retaining structures. It is based on the limit equilibrium method, but it uses some additional conditions for interaction between the retaining structure and the ground, when referring to the distribution of the mobilized earth pressures on the structure. The greatest benefit of the proposed method is shown in the analysis of structures of layered ground (heterogeneous above the dredge level and homogeneous below it), embedded in frictional and cohesive materials, and in the possibility of considering the influence of surcharge loadings on the active or passive side of the retaining structure. When analyzing such cases in practice, the proposed method gives results which are in better agreement with the results of FEM based elasto-plastic interaction analyses than with the results of currently used methods. At the same time, its results are in accordance with those published for homogeneaus cohesionless ground. Since in practice almost all retaining structures are erected in layered ground (heterogeneaus above the dredge level and homogeneous below it), the proposed method is very convenient and applicable for the analyses and design of cantilever structures under arbitrary geomechanical conditions.
Keywords: geomechanics, soil-structure interaction, retaining walls, embedment, cantilevers, earth pressure, pressure distribution, friction soil - wall, limit analysis, shear forces
Published in DKUM: 17.05.2018; Views: 1460; Downloads: 83
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6. The assesment of pile shaft resistance based on axial strain measurements during the loading testAndrej Štrukelj, Stanislav Škrabl, Ksenija Štern, Janko Logar, 2005, original scientific article Abstract: Near Maribor, a new bridge over the Drava river is being under construction. Before the main works actually started, static and dynamic loading tests of piles were performed. The goal of the static loading test was to determine the bearing capacitiy of the test pile. It was also interesting to determine the share of the axial load distributed on the shaft and pile toe. In order to measure the distribution of the axial force along the pile, a specially made steel canal was built in the pile before concreting. Inside this canal the strain gauges were distributed evenly at the distance of one meter. The strains were measured for each loading phase in all measuring points. The distribution of the axial force was assessed from the obtained results and based on the distribution of the axial force the shaft resistance could be determined. The unexpectedly high bearing capacity of the pile shaft made the obtained results highly interesting. In this paper, measuring methods and measuring results are discussed. Behaviour of the pile and the soil during the loading test were also modelled by axial symmetric and three dimensional models. The calculated and measured results show a very good agreement.
Keywords: civil engineering, bridges, soil mechanics, pile shaft resistance, loading test, strain measurements, elastoplastic soil modelling, finite element method
Published in DKUM: 16.05.2018; Views: 1430; Downloads: 83
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7. Primerjava gradnje predorov v Sloveniji in tujini s poudarkom na gradnji Baznega predora GotthardLucia Boršić, 2017, diploma project paper Abstract: Projektna naloga temelji na primerjavi gradnje predorov v Sloveniji in predorov v tujini, s poudarkom na primerjavi gradnje Baznega predora Gotthard, ki predstavlja najdaljši in najgloblji predor na svetu, z gradnjo večjih predorov zgrajenih na območju Slovenije. Naloga prikazuje cilje posameznih projektov, idejne zasnove, probleme in izzive s katerimi so se srečevali inženirji in delavci pri sami gradnji, geološko raznolikost in zgodovino izgradnje predorov.
Uporaba sodobnih tehnologij pri gradnjah predorskih cevi lahko bistveno prispeva k povečanju hitrosti gradnje in omogoča obvladovanje stroškov ter zagotavlja višji nivo zanesljivosti in varnosti pri gradnjah, ki je pri klasičnih ročnih izkopih s številnimi manj usposobljenimi delavci skoraj ni bilo mogoče zagotoviti. Glavni problemi se načeloma pojavljajo v prelomih hribinskih mas, prehodih med geološkimi formacijami in na območjih, kjer je prisotna večja količina talne vode, nevarnih plinov (metan) ter tudi na območjih z majhnimi nadkritji, kjer se pogosto graditelji odločajo za gradnjo pokritih vkopov in drugih zahtevnejših tehničnih rešitev (Koroški pokrov, cevni ščiti itd.). Večje razlike se pojavijo v kolikor primerjamo gradnjo predorov pod morjem ( Eurotunnel, Seikan, Marmaray,…) z gradnjo v hribinah (Bazni predor Lötschberg, Delaware Aqueduct, Bohinjski železniški predor, Karavanški,...).
Keywords: gradbeništvo, predori, Karavanški predori, Bohinjski predor, Gotthard Bazni predor
Published in DKUM: 25.08.2017; Views: 2274; Downloads: 250
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8. Geodetski monitoring na osnovi gnss opazovanj na nestabilnih tlehAndrej Drajzibner, 2017, master's thesis Abstract: Naloga predstavlja primer izvedbe geodetskega monitoringa z geološkimi raziskavami na nestabilnih tleh, združenega v praktičnem in teoretičnem delu.
V prvem delu so opredeljene GNSS-metode za spremljanje premikov plazov, prikazane so tudi geološko-hidrološke raziskave.
V vsakdanji praksi je uporaba globalnih navigacijskih sistemov in GNSS-metod izmere venomer pogostejša, saj so te preproste za uporabo. V primerjavi s klasičnimi terestričnimi metodami izmere v veliko primerih zagotavljajo hitrejšo in enostavnejšo geodetsko izmero.
V drugem delu je prikazan praktičen primer izvedbe monitoringa na izbranem območju. V namen prikaza praktičnega primera so bile v sklopu terenskih raziskav izvedene geološko-geomehanske raziskave tal in GNSS-meritve. Na podlagi teh je bilo mogoče spremljati pomike tal v daljšem časovnem intervalu. Dobljeni rezultati so omogočili ocenitev karakteristik tal in velikosti pomikov, na osnovi katerih smo oblikovali mnenje stanja območja in opredelili možne sanacijske ukrepe.
Keywords: GNSS monitoring, geodetske meritve, pomiki, geološke raziskave
Published in DKUM: 10.07.2017; Views: 1939; Downloads: 202
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10. KONTROLIRANO ZNIŽEVANJE TALNE VODE V GRADBENIH JAMAHAlen Čatak, 2016, master's thesis Abstract: Magistrsko delo obravnava tehnologijo črpanja talne vode iz gradbenih jam od začetka izkopa gradbene jame do konca gradnje objekta v takšnem okviru, da gradnja poteka zanesljivo, izvedljivo in ekonomično. Magistrsko delo opisuje postopke varovanja gradbenih jam in črpanja talne vode iz gradbenih jam. Kot primer je prikazano črpanje talne vode v gradbeni jami v času izgradnje »Javne podzemne garaže Kapucinski trg« v Varaždinu.
Cilj dela je na podlagi analize primera črpanja talne vode iz gradbene jame mogoče dokazati varovanje pred talno vodo kot zanesljivo, izvedljivo in ekonomično v celotnem času izgradnje objekta.
Keywords: geotehnika, gradbena jama, AB diafragma, talna vode, črpanje
Published in DKUM: 17.01.2017; Views: 2219; Downloads: 271
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