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Coulomb Criterion (coulomb + criterion)

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Engineering100%

Selected Abstracts

Numerical analysis of the response of battered piles to inclined pullout loads

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 10 2009
Hussein Mroueh
Abstract This paper presents a three-dimensional finite element analysis of the response of battered piles to the combined lateral and vertical pullout loads. Analyses are carried out using an elastoplastic constitutive law based on the non-associated Mohr,Coulomb criterion. The influence of the contact condition at the pile,soil interface is also investigated. Analyses show that the load's inclination with regard to the pile's axis affects both the lateral and axial response of the battered piles. Analyses also show that the pullout capacity of battered piles is affected by the pile's inclination regarding the vertical axis as well as the load's inclination regarding the pile's axis. The investigation of the influence of the contact condition at the soil,pile interface shows that the possibility of sliding at the soil,pile interface affects the response of battered piles subjected to loads with low inclination regarding the pile's axis. Copyright © 2008 John Wiley & Sons, Ltd. [source]

A discrete model for the dynamic propagation of shear bands in a fluid-saturated medium

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 2 2007
Julien Réthoré
Abstract The first part of this manuscript discusses a finite element method that captures arbitrary discontinuities in a two-phase medium by exploiting the partition-of-unity property of finite element shape functions. The fluid flow away from the discontinuity is modelled in a standard fashion using Darcy's relation, and at the discontinuity a discrete analogy of Darcy's relation is used. Subsequently, dynamic shear banding is studied numerically for a biaxial, plane-strain specimen. A Tresca-like as well as a Coulomb criterion is used as nucleation criterion. Decohesion is controlled by a mode-II fracture energy, while for the Coulomb criterion, frictional forces are transmitted across the interface in addition to the cohesive shear tractions. The effect of the different interface relations on the onset of cavitation is studied. Finally, a limited quantitative study is made on the importance of including a so-called dynamic seepage term in Darcy's relation when considering dynamic shear banding. Copyright © 2006 John Wiley & Sons, Ltd. [source]

A numerical study of flexural buckling of foliated rock slopes

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2001
D. P. Adhikary
Abstract The occurrence of foliated rock masses is common in mining environment. Methods employing continuum approximation in describing the deformation of such rock masses possess a clear advantage over methods where each rock layer and each inter-layer interface (joint) is explicitly modelled. In devising such a continuum model it is imperative that moment (couple) stresses and internal rotations associated with the bending of the rock layers be properly incorporated in the model formulation. Such an approach will lead to a Cosserat-type theory. In the present model, the behaviour of the intact rock layer is assumed to be linearly elastic and the joints are assumed to be elastic,perfectly plastic. Condition of slip at the interfaces are determined by a Mohr,Coulomb criterion with tension cut off at zero normal stress. The theory is valid for large deformations. The model is incorporated into the finite element program AFENA and validated against an analytical solution of elementary buckling problems of a layered medium under gravity loading. A design chart suitable for assessing the stability of slopes in foliated rock masses against flexural buckling failure has been developed. The design chart is easy to use and provides a quick estimate of critical loading factors for slopes in foliated rock masses. It is shown that the model based on Euler's buckling theory as proposed by Cavers (Rock Mechanics and Rock Engineering 1981; 14:87,104) substantially overestimates the critical heights for a vertical slope and underestimates the same for sub-vertical slopes. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Three-dimensional Mohr,Coulomb limit analysis using semidefinite programming

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 11 2008
K. Krabbenhøft
Abstract Recently, Krabbenhøft et al. (Int. J. Solids Struct. 2007; 44:1533,1549) have presented a formulation of the three-dimensional Mohr,Coulomb criterion in terms of positive-definite cones. The capabilities of this formulation when applied to large-scale three-dimensional problems of limit analysis are investigated. Following a brief discussion on a number of theoretical and algorithmic issues, three common, but traditionally difficult, geomechanics problems are solved and the performance of a common primal,dual interior-point algorithm (SeDuMi (Appl. Numer. Math. 1999; 29:301,315)) is documented in detail. Although generally encouraging, the results also reveal several difficulties which support the idea of constructing a conic programming algorithm specifically dedicated to plasticity problems. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Lower bound limit analysis of cohesive-frictional materials using second-order cone programming

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 4 2006
A. Makrodimopoulos
Abstract The formulation of limit analysis by means of the finite element method leads to an optimization problem with a large number of variables and constraints. Here we present a method for obtaining strict lower bound solutions using second-order cone programming (SOCP), for which efficient primal-dual interior-point algorithms have recently been developed. Following a review of previous work, we provide a brief introduction to SOCP and describe how lower bound limit analysis can be formulated in this way. Some methods for exploiting the data structure of the problem are also described, including an efficient strategy for detecting and removing linearly dependent constraints at the assembly stage. The benefits of employing SOCP are then illustrated with numerical examples. Through the use of an effective algorithm/software, very large optimization problems with up to 700 000 variables are solved in minutes on a desktop machine. The numerical examples concern plane strain conditions and the Mohr,Coulomb criterion, however we show that SOCP can also be applied to any other problem of lower bound limit analysis involving a yield function with a conic quadratic form (notable examples being the Drucker,Prager criterion in 2D or 3D, and Nielsen's criterion for plates). Copyright © 2005 John Wiley & Sons, Ltd. [source]