Effect of particle roundness and morphology on the shear failure mechanism of granular soil under strip footingBabak Karimi Ghalehjough
, Suat Akbulut
, Semet Çelik
, 2018, original scientific article
Abstract: This study investigates the effect of particles roundness and morphology on the shear failure mechanism of soil. A strip footing was modeled under laboratory conditions. Calcareous soil was tested with three roundness classes: angular, rounded and well-rounded shapes with sizes of 0.30 mm to 4.75 mm. These were divided into six different groups at three relative densities of 30%, 50% and 70%. A series of photographs was taken during the tests and analyzed using the particle image velocimetry (PIV) method to understand the soil-deformation mechanism. The results showed that increasing the sample sizes increased the affected area of the soil. At the same time, increasing the relative density caused a punching failure mechanism that went towards the general failure. The shear failure mechanism of the soil changed from general toward punching shear failure with increasing particle roundness. This effect was larger with the smaller materials. Underneath the affected layers of soil, the angular samples were deeper than the rounded and well-rounded samples. The affected depth in the angular soil was approximately 1.5B in the smallest size group. This was more than 3B and near 4B in the largest size group. Both the sides and the underlying soil layers should be considered on angular soils. The area under the footing becomes more important than the side parts after increasing the roundness of the particles.
Keywords: particle roundness, morphology of particles, shear failure mechanism, strip footing, PIV method, ultimate bearing capacity
Published in DKUM: 11.10.2018; Views: 1063; Downloads: 392
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Analytical and numerical factor of safety (uls) calculations on reinforced embankmentsTadej Vidnar
, 2017, master's thesis
Abstract: This thesis deals with factor of safety calculations on geogrid reinforced embankments carried out by commonly used limit equilibrium (LEM) and finite element methods (FEM). The study utilize LEM based software SLIDE and FEM based software PHASE2. The main difference between these two approaches is that the LEM methods are based on the static of equilibrium whereas FEM methods utilise the stress strain relationship. Unlike to LEM, numerical analysis also computes displacements.
For practical example of a geogrid reinforced embankment the factor of safeta (FoS) is calculated. Reinforced soil structures are nowadays utilized for a lot of civil engineering applications. Traditionally, the design of geogrid reinforced soil is performed using analytical methods (LEM). Unfortunately, these methods missing the fundamental physics of stress-strain relationship and are therefore not able to compute a realistic stress distribution.
In first step of the analysis the FoS is carried out with analytical approach. The most rigorous LEM methods, Bishop’s, Spencer’s and Morgenstern-Price are selected and the FoS for circular and polygonal slip surface is calculated.
In second step of the analysis the FoS is carried out with numerical approach. Shear strength reduction (SSR) procedure was performed to determine the critical strength reduction factor (SRF) which represents the FoS of slope.
Keywords: civil engineering, finite element method (FEM), limit equilibrium method (LEM), embankments, slope stability, bearing capacity failure, geosynthetics, geogrids, shear strains
Published in DKUM: 27.09.2017; Views: 928; Downloads: 166
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Application of the european SINTAP procedure to the failure analysis of a broken forkliftNenad Gubeljak
, Uwe Zerbst
, Jožef Predan
, Maks Oblak
, 2004, original scientific article
Abstract: The recently developed European flaw assessment procedure SINTAP was applied to the failure analysis of a broken fork of a forklift. Based on the service load at failure, critical crack sizes were determined at different analysis levels of the procedure. It was shown in the present case study that the failure was caused by defective design.
Keywords: structural integrity, mechanics of structures, forklift, fracture mechanics, critical crack size, failure analysis, SINTAP procedure, load bearing capacity
Published in DKUM: 01.06.2012; Views: 1681; Downloads: 82
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