Iskanje po katalogu digitalne knjižnice

Opis: 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.
Ključne besede: soil mechanics, passive earth pressure, upper bound theorem, optimization, three-dimensional failure mechanism
Objavljeno v DKUM: 18.05.2018; Ogledov: 1324; Prenosov: 73
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Opis: Geophysics has been developed in order to supply indicative estimations in soil mechanics like the grain size distribution of finely grained soils as day, silt and fine sands. The paper describes the attempt to characterize porous and saturated marine sediments with a non destructive technique which is the acoustic wave, in order to determine the correlation with geotechnical measurements. The characterization of physical parameters of marine sediments was based on research methods which permit to describe the parameters defining different types of sediment and zones of sedimentation; to determine fundamental parameters that influence the propagation of the acoustic waves in saturated and porous means; to define quick and indicative methods for characterization of physical parameters of analysed means. The acoustic measurements were carried out at SACLANT-NATO of La Spezia (I), where the Vertical Multi Sensor Core Logger (V-MSCL) was used. The results of acoustic tests were compared to the grain size curves of the sediments and the propagation characteristics such as velocity, density, porosity and absorption of experimentally determined data. The analyses are based 011 various mathematical models presented in. literature, in order to predict and to describe physical mechanisms of the wave propagation using a simplification of the sediment structure. The target of the study was to determine a new mathematical law that linked the mean grain size to a directly measurable parameter such as the spectral amplitude, and to offer the possibility to obtain the first indicative value of the sediment mean grain size. The determined exponential law represents an innovative and quick approach to determine a physical characteristic of saturated and porous sediments such as the grain size in a non destructive way based on the spectral analysis of the wave propagation form.
Ključne besede: soil mechanics, marine sediments, finely grained soil, acoustic waves, grain size curve
Objavljeno v DKUM: 17.05.2018; Ogledov: 1211; Prenosov: 173
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Opis: The relationship between the water content and the undrained shear strength of finely grained soils can be described with a nonlinear function in which the type of soils is determined by two parameters. These parameters depend primarily on the size of clay minerals, their quantity in soil composition and the interlayer water quantity in expanding clay minerals. This article asserts that there exists also the exactly defined relationship also between the water content and consolidation pressure. In the function describing this relationship, the type of soil is determined by two parameters. They can be expressed depending on the same mineralogical properties of soils as the values of parameters in the function showing the relationship between the water content and the undrained shear strength. These findings allow us to express the ratio between undrained shear strength and consolidation pressure depending on mineralogical properties of soils.
Ključne besede: soil mechanics, properties of soils, clays, specific surface, undrained shear strenght, compressibility
Objavljeno v DKUM: 15.05.2018; Ogledov: 1513; Prenosov: 112
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Opis: The cone penetrometer method is being increasingly used for the determination of the liquid limit of cohesive soils. The same method can be used to determine the plastic limit according to the known relationship between soil moisture content and depth of cone penetration. This relationship is non-linear, yet becomes linear on a log-log scale resulting in a simple methodof determination of liquid limit and plastic limit values. This technical note determines the soil properties that define these index parameters. Experimentally obtained results suggest that the index parameters primarily depend on the type, size, and quantity of the clay minerals in soil.Soil index parameters such as the liquid limit and plastic limit can be determined from knowledge of the mineralogical properties of the soil because this dependence appears well defined.
Ključne besede: soil mechanics, soil tests, clays, cohesive soils, soil properties, Attenberg limits, cone penetration tests
Objavljeno v DKUM: 01.06.2012; Ogledov: 2316; Prenosov: 63
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Opis: The topic of this paper is to show that the integrals of infinite extent representing the surface displacements of a layered half-space loaded by a harmonic, vertical point load can be reduced to integrals with finite integration range. The displacements are first expressed through wave potentials and the Hankel integral transform in the radial coordinate is applied to the governing equations and boundary conditions, leading to the solutions in the transformed domain. After the application of the inverse Hankel transform it is shown that the inversion integrands are symmetric/antimetric in the transformation parameter and that this characteristic is preserved for any number of layers. Based on this fact the infinite inversion integrals are reduced to integrals with finite range by choosing the suitable representation of the Bessel function and use of the fundamental rules of contour integration, permitting simpler analytical or numerical evaluation. A numerical example is presented and the results are compared to those obtained by the CLASSI program.
Ključne besede: civil engineering, soil mechanics, Green`s function, layered half-space, vertical point load
Objavljeno v DKUM: 31.05.2012; Ogledov: 2472; Prenosov: 42
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