Bearing capacity of surface footings by finite elements

Manoharan, N.; DasGupta, Sunando

doi:10.1016/0045-7949(94)00381-c

Cited by 90 publications

(52 citation statements)

References 20 publications

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“…In reality, however, as discussed by Salgado (2008) and Lyamin et al (2007), it is the basis of comparison of strip and circular footings that is different. MOC, limit analysis and FE analyses (Manoharan & Dasgupta, 1995;Loukidis & Salgado, 2009b), assuming that the soil follows the Mohr-Coulomb (M-C) failure criterion (same friction angle irrespective of nearly triaxial compression conditions or plane-strain conditions), will indeed produce s ª .1. But, in reality, the friction angle under triaxial compression conditions is smaller than that under plane-strain conditions for the same D R , which leads to s ª , 1 if D R is the basis of comparison.…”

Section: Effect Of Pressure Level On Bearing Capacitymentioning

confidence: 99%

Effect of relative density and stress level on the bearing capacity of footings on sand

Loukidis¹,

Salgado²

2011

Géotechnique

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The design of shallow foundations relies on bearing capacity values calculated using empirical procedures that are based in part on solutions obtained using the method of characteristics, which assumes a soil that is perfectly plastic following an associated flow rule. In this paper the problem of strip and circular footings resting on the surface of a sand layer is analysed using the finite-element method. Analyses are performed using a two-surface plasticity constitutive model that realistically captures the aspects of the mechanical response of sands that are relevant to the bearing capacity problem. In particular, the model accounts for non-associated flow, strain-softening, and both stress-induced and inherent anisotropy. Based on the results of the analyses, the paper examines the validity of the bearing capacity factors N ª and shape factors s ª used in practice. A relationship for determining appropriate values of friction angle for use in bearing capacity calculations is also proposed.KEYWORDS: anisotropy; bearing capacity; footings/foundations; numerical modelling; plasticity; sands L'étude de fondations peu profondes repose sur des valeurs de force portante calculées en utilisant des procé-dures empiriques, basées en partie sur des solutions obtenues avec la méthode des caractéristiques, qui pré-suppose la présence d'un sol parfaitement plastique en suivant une règle d'écoulement connexe. Dans la présente communication, on a analysé le problème de semelles filantes et circulaires posées sur la surface d'une couche de sable, avec la méthode aux éléments finis. Des analyses ont été effectuées en utilisant un modèle constitutif de plasticité de deux surfaces, exprimant, de façon réaliste, les aspects de la réaction mécanique des sables dans le contexte du problème de la force portante. Ce modèle se penche notamment sur le débit non associé, sur le radoucissement, ainsi que sur l'anisotropie par pression et inhérente. Sur la base des résultats des analyses, la communication examine la validité des facteurs de force portante N ª et des facteurs de forme s ª utilisés dans la pratique. En outre, on propose également un rapport pour la détermination de valeurs appropriées de l'angle de frottement pour les calculs de la force portante.

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Section: Effect Of Pressure Level On Bearing Capacitymentioning

confidence: 99%

Effect of relative density and stress level on the bearing capacity of footings on sand

Loukidis¹,

Salgado²

2011

Géotechnique

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“…With the use of finite element analysis, logspiral zones are obtained by some researchers so far (Conte et al [13] ), but not all. Manoharan and Dasgupta [33] discovered radial shear zone and Yamamoto and Otani [55] obtained circular surface zone by finite element analysis, while Yamamoto and Kusuda [53] applied upper bound analysis to get circular surface transition zone. The authors have also tried several finite element programs, and logspiral failure zone as shown in Fig.15 is obtained for the case of Nc by Plaxis.…”

Section: Discussion and Comparisons With Laboratory Testmentioning

confidence: 99%

“…The ultimate bearing capacity for shallow foundations with simple geometry has been solved by many investigators. The methods of analysis can be classified into the following four categories: (1) the limit equilibrium method [50,36,37] ; (2) the method of characteristics [44,47,21,1,6,11] ; (3) the upper/lower-bound plastic limit analysis [45,46,75,16,38,39,40,48,22,26,27,28,51,30,31,29] ; and (4) numerical methods based on either the finite-element technique (FEM) or finite-difference method [20,33,17] . For the first three groups of methods, only the ultimate condition is considered, and a simple perfectly plastic soil model is commonly assumed.…”

Section: Testmentioning

confidence: 99%

Transition zone in Bearing Capacity Problem from Plasticity Method, Discrete Element Method and Laboratory tests

Cheng

2018

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Abstract:In this paper, the classical bearing capacity problem and the logspiral transition zone are re-considered from a continuum plasticity approach as well as discrete element approach. In the discrete element approach, the bearing capacity problem is considered from the elastic stage, plastic stage to the final rupture stage. It is found that there are noticeable differences in the failure mechanism between the continuum and discontinuum analyses, and the well-known logspiral transition zone is also not apparent in both the discrete element approach, plasticity approach as well as the laboratory tests. With the increase in the friction angle of soil, the transition zone is becoming more like a wedge zone than a logspiral zone as found from the present study.

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“…Such a transition can be associated with the inflection point in the settlement distribution, whose location is markedly affected by the soil non-associativeness (setting ϕ* ¼ ϕ -i.e. ψ ¼ ϕ -in equation (13) Vermeer, 1984;Manoharan & Dasgupta, 1995;Frydman & Burd, 1997;Yin et al, 2001;Loukidis & Salgado, 2009) and (b) the deviatoric π-section of the MMC failure locus circumscribes the Mohr-Coulomb locus considered in the Terzaghi formula (8). The interplay between these two factors produces plane-strain bearing capacities larger than standard predictions based on associative Mohr-Coulomb plasticity (deviations in the order of 13%).…”

Section: Strip Footing Fe Modellingmentioning

confidence: 99%

A macroelement framework for shallow foundations including changes in configuration

2016

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Macroelement plasticity models are being increasingly applied to study non-linear soil–foundation interaction (SFI) problems. Macroelement models are particularly appealing from a computational standpoint, as they can capture the essence of SFI by means of a few degrees of freedom. However, all the macroelement formulations available in the literature suffer from the same limitation, that is the incapability of accounting for changes in both geometry and loading/boundary conditions. Accordingly, macroelement models are usually calibrated to analyse a given boundary value problem, with no chance of handling situations with significant variations in embedment, lateral surcharge and/or phreatic level. The present work shows how standard soil modelling concepts can be exploited to reproduce relevant ‘configurational features’ of non-linear SFI. A macroelement framework is here proposed to simulate the drained load–settlement response of shallow footings on sand in the presence of varying surface/body forces. As a first step, the ideal case of a weightless soil layer is exclusively considered. The macroelement constitutive equations are conceived/calibrated on a minimal set of finite-element results; the satisfactory predictive capabilities of the macroelement model are finally demonstrated by retrospectively simulating selected finite-element tests.

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Bearing capacity of surface footings by finite elements

Cited by 90 publications

References 20 publications

Effect of relative density and stress level on the bearing capacity of footings on sand

Effect of relative density and stress level on the bearing capacity of footings on sand

Transition zone in Bearing Capacity Problem from Plasticity Method, Discrete Element Method and Laboratory tests

A macroelement framework for shallow foundations including changes in configuration

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