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Ground-sourced energy wells for heating and cooling of buildings
Heinz Brandl, Dietmar Adam, Roman Markiewicz, 2006, izvirni znanstveni članek

Opis: Energy wells are thermo-active elements for an economical extraction or storage of ground energy, similar to energy piles and other deep foundation elements also used as heat exchangers. Heating and/or cooling of buildings requires a primary and secondary thermo-active circuit, commonly connected by a heat pump. The paper gives several design aspects of energy wells which can be also used for the design of deep energy foundations. Thermal response tests have proved suitable for the in-situ determination of thermal ground properties required for an optimised design. Moreover, different systems of energy wells are discussed, and a comprehensive pilot research project is described.
Ključne besede: energy wells, energy foundations, geothermal geotechnics, geothermal heating/cooling, thermo-active structures, thermal ground properties, field testing
Objavljeno: 17.05.2018; Ogledov: 7; Prenosov: 0
.pdf Celotno besedilo (4,24 MB)

Ludvik Trauner, 2006, predgovor, spremna beseda

Ključne besede: editorials, scientific journals, geomechanics, geotechnical engineering
Objavljeno: 17.05.2018; Ogledov: 11; Prenosov: 0
.pdf Celotno besedilo (35,41 KB)
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New trends in rock mass characterisation for designing geotechnical structures
Drago Ocepek, 2005, izvirni znanstveni članek

Opis: The investigation on designing supporting measures for geotechnical structures consists of the proper selection of the input data for the stress – strain analysis of the excavation process and the selection of retaining measures. In the preliminary phase of investigation the area must be geologically mapped in detail, and discontinuities precisely measured, boreholes and their “in situ” tests listed and samples for laboratory examinations taken. The new method allows rock mass classification for different rock quality, from soft rocks to mixed rock masses, as well as determination of the geological strength index GSI. The limits for using the suggested method are persistent discontinuities in rock mass which lead to translation or rotation failure mechanisms, either in a single plane or as a wedge. In all cases where discontinuities play a significant role, the rock mass structure must be considered and kinematical analyses performed. In other circumstances, a rock may be uniform and reasonably isotropic due to the geometry of discontinuities and their mutual intersections. The value range of GSI is first determined in the beginning of investigation and later in the excavation phase by considering the disturbance factor D, which expresses disturbances caused by excavation methods and rock mass relaxation. The strength and deformability parameters of rocks of different quality are determined by the generalized Hoek-Brown failure criterion and applied to shallow and deep tunnels or slopes. Before the start of excavations work and after establishing the retaining measures, the analysis results are checked by monitoring. New methods include the determination of post peak strength parameters of rock mass after relaxation, and routine measurements. The newest measurement system however allows direct readings of displacements of the rock mass in both the elastic and post-peak states. With back analyses we determine the softening behavior of the rock mass and a possible need for increasing retaining measures. Such a design method enables the optimization of retaining measures and the reduction of investment costs.
Ključne besede: geological strength index – GSI, simulation of a triaxial large scale »in situ« test, numerical modeling, retaining measures, rock reinforcement, monitoring, back analyses, strain softening, rock mass relaxation
Objavljeno: 16.05.2018; Ogledov: 40; Prenosov: 0
.pdf Celotno besedilo (1,05 MB)

The assesment of pile shaft resistance based on axial strain measurements during the loading test
Andrej Štrukelj, Stanislav Škrabl, Ksenija Štern, Janko Logar, 2005, izvirni znanstveni članek

Opis: 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.
Ključne besede: civil engineering, bridges, soil mechanics, pile shaft resistance, loading test, strain measurements, elastoplastic soil modelling, finite element method
Objavljeno: 16.05.2018; Ogledov: 36; Prenosov: 0
.pdf Celotno besedilo (987,58 KB)

The anchored pile wall optimization using NLP approach
Helena Vrecl-Kojc, 2005, izvirni znanstveni članek

Opis: The type of a retaining structure as well as the structure configuration mainly depends on geological conditions. If geological, urban and other data allow an alternative, the costs should also be considered as an important factor. In geotechnical practise, pile walls are especially used in excavations, in the erection of traffic facilities and in the sanitation of landslides. This paper is aimed at presenting economical differences between cantilever and anchoring pile walls and the impact of different parameters on costs. The optimization method, which uses mathematical programming, gives an optimal solution to geometry, self-manufacturing costs, and other characteristics of the structure in a uniform optimization process. This paper presents the optimization process using the nonlinear programming (NLP) approach for the anchored pile wall. The application presented only serves to confirm the effectiveness of the proposed optimization method. Therefore, the retaining structure is situated in homogeneous non-cohesive soil at three different soil friction angles of 35°, 30° and 25°. The generalized analytical method, the USA method, which was first introduced by Bowles [3], isused in the application. The analysis of the results shows the impact of parameters, the main controlling factors, configuration geometry and savings. The optimal results allowed from 18 up to 47 per cent savings compared to the cantilever pile wall depending on ground and structure input data and the excavation depth.
Ključne besede: civil engineering, optimum design, retaining structures, USA analytical method, nonlinear programming
Objavljeno: 16.05.2018; Ogledov: 38; Prenosov: 0
.pdf Celotno besedilo (216,45 KB)

Ludvik Trauner, 2005, predgovor, spremna beseda

Ključne besede: editorials, scientific journals, geomechanics, geotechnical engineering
Objavljeno: 16.05.2018; Ogledov: 40; Prenosov: 0
.pdf Celotno besedilo (35,39 KB)
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Suggestion about determination of the bearing capacity of piles on the basis of CPT sounding tests
József Pusztai, 2005, izvirni znanstveni članek

Opis: The Cone Penetration Test (CPT) is a well-recognized tool for the calculation of the ultimate bearing capacity of piles. Within the Hungarian physiographic territory, the CPT and Static Pile Load Tests of the bored (Continuous Flight Auger - CFA, protective tube) and driven (Franki) piles installed in different soils (gravel, sand and clay) were compared to determine the ultimate bearing capacity of piles by using new formulae.
Ključne besede: bearing capacity of piles, cone penetration test
Objavljeno: 15.05.2018; Ogledov: 65; Prenosov: 1
.pdf Celotno besedilo (155,29 KB)

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: 60; Prenosov: 3
.pdf Celotno besedilo (586,91 KB)

Cyclic liquefaction potential of lacustrine carbonate from Julian Alps
Bojan Žlender, Stanislav Lenart, izvirni znanstveni članek

Opis: This paper presents the liquefaction studies of lacustrine carbonate silt from the Julian Alp landslide Stože. Geological conditions of the region and geomechanical characteristics of the ground were investigated. The research project was performed with the intention to determine the effects of cyclic loading on lacustrine carbonate silt. Investigation with 77 cyclic triaxial tests was performed on universal triaxial apparatus Wykeham Farrance UP 100 TR, in the Laboratory of soil mechanics, Faculty of Civil Engineering, University of Maribor. The essential equipment comprises cylindrical triaxial apparatus with a cell, a press with appurtenant electro-mechanic equipment, measuring equipment, and computer hardware and software equipment. Specimens with dimensions of height = 140 mm and diameter = 70 mm were saturated, then subjected to the arbitrary initial isotropic stress state and consolidated with vertical and radial draining, and then loaded with distortional loading of chosen dynamical axial force (frequency f = 1 Hz). A set of tests with a spectrum of different stress states and cyclic loading were performed. This research showed that lacustrine carbonate silt is a highly sensitive material.The resistance to liquefaction was somewhat higher than that of typical clean sand, but a perceivable excess pore pressure generation, which causes the decrease of strength parameters, was noticed. Test results of cyclic triaxial tests indicate dynamic characteristics of lacustrine carbonate silt and wide applicability of the test method.
Ključne besede: civil engineering, geomechanics, soil investigations, lacustrine carbonate silt, cyclic triaxial tests, liquefaction potential, shear modulus, damping ratio, cyclic stress ratio, pore pressure ratio
Objavljeno: 15.05.2018; Ogledov: 57; Prenosov: 1
.pdf Celotno besedilo (1,53 MB)

Green's function for an elastic layer loaded harmonically on its surface
Tomaž Pliberšek, Andrej Štrukelj, Andrej Umek, 2005, izvirni znanstveni članek

Opis: The Green's function in surface displacement plays an important role in soil structure interaction. In evaluating the Green's function, several difficulties occur because it is formulated in the infinite integral form. This paper outlines a method of analyzing the steady-state dynamic response of an elastic layer subjected to general point load excitation. It is assumed that the load is applied at the surface. The application Hankel integral transform, to the governing differential equations and boundary conditions yields the response displacements at the surface in integral representation. It will be shown that these semi-infinite integrals can be reduced to the integral with the finite range of integration, which can be efficiently taken numerically. The numerical results are presented, which show the efficiency of the developed procedure.
Ključne besede: civil engineering, geomechanics, soil-structure interaction, layered halfspace, Green's function, elastodynamics
Objavljeno: 15.05.2018; Ogledov: 56; Prenosov: 0
.pdf Celotno besedilo (375,59 KB)

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