1. 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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2. 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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3. Upper-bound solutions of three-dimensional passive earth pressuresStanislav Škrabl, Borut Macuh, 2005, original scientific article Abstract: This paper presents a novel approach to the determination of passive soil pressures: using the upper-bound method within the framework of limit analysistheory. It is based on a three-dimensional, kinematically admissible, rotational, hyperbolical failure mechanism. The failure mechanism is composed of the central and two lateral bodies, which are connected by a common velocity field. This approach is similar to two-dimensional stability analyses, where the log spiral potential failure surface is considered. The front surface of the central body interacts with the retaining wallč the uppersurface can be loaded by surcharge loadingč and the log spiral segment defines the curved failure surface of the central part. The cross sections of the lateral bodies are in agreement with the cross section of the central body. On the outer side, they are laterally bounded by a curved and kinematically admissible hyperbolic surface, which is defined by enveloping the hyperbolical half cones and part of the case surface of the leading half cone. The results give values for the passive soil pressure coefficients that are for most cases lower than the values determined by the upper-bound method of limit analysis for a translational failure mechanism, as published in the literature.
Keywords: geomechanics, soil-structure interaction, limit analysis, earth pressures, passive pressure, failure surface
Published in DKUM: 01.06.2012; Views: 1923; Downloads: 106
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4. Passive earth pressure determination : application of the corresponding state theorem for calculating upper-bound valuesBorut Macuh, Stanislav Škrabl, 2010, original scientific article Abstract: The validity of some limit state solutions, when strictly applied to the basic corresponding state theorem (Caquot, 1934), is limited and valid only for simpler limit states, where stress vectors are either perpendicular to the boundary surfaces or when the direction of stress eigenvalue trajectories in transformation are preserved (Michalowski, 2001). The theorem of corresponding states allows us, in some cases, to attain solutions belonging to the limit states for cohesive-friction materials with the transformation of the known boundary of elasto-plastic solutions of limit states for pure friction materials. We demonstrated that for the selected kinematically admissible model, in general cases of boundary stresses, the indirect application of the corresponding states theorem in modified form is permitted.To determine this, we applied the kinematic approach of limit state analysis and used the upper-bound theorem for determining passive earth pressures. The results of our analyses show that incautious application of the corresponding state theorem in its basic form and for general cases is in admissible because the results obtained can be correct only coincidentally, depending on the boundary conditions
Keywords: corresponding state, earth pressure, passive pressure, limit analysis, upper-bound
Published in DKUM: 31.05.2012; Views: 1941; Downloads: 102
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