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In this article, the response of an interfacial layer developed along a particulate–continuum interface is explored under two opposite normal confining constraints. To this end, a cohesionless granular strip subjected to both isochoric and non-isochoric conditions is monotonously sheared against an adjacent wall of different surface roughness values. Numerical simulations are performed using a finite element method formulated within an elasto-plastic polar continuum, equipped by granular rotation, couple stress, and average grain size. Along the wall in motion, the slide and rotation resistance of the first layer of boundary grains are innovatively determined by the additional polar boundary conditions, taking into account a ratio between slip and granular rotation along the wall, asperities of wall surface, and grain size. In particular, the combined interaction of material dilatancy constraint and wall roughness are examined on the frictional resistance and deformation of the interfacial layer. It is shown that the normal confinement and the roughness geometry of the wall surface have visible impacts on the stress-displacement response of the interfacial layer. The evolution of stresses and couple stresses is entirely different in isochoric and non-isochoric conditions. However, the stationary value of the interfacial strength is independent of how the bounding wall confines the granular body. Besides, the deformations manifested out of the interfacial layer are more pronounced in isochoric shearing than non-isochoric shearing. Nevertheless, the location and progression of the interfacial layer do not necessarily depend on the applied confining constraint after large shearing. [ABSTRACT FROM AUTHOR]

This article presents the interface shearing behaviour of a granular soil layer in contact with a bounding structure under motion. For this purpose, an elasto-plastic Cosserat continuum model (EPCCM) and finite element method (FEM) in the updated Lagrange frame are employed. Plane quasi-static shearing of a granular soil layer, bounded by upper and lower rigid boundaries with different surface roughness conditions, is simulated under free dilatancy and constant vertical pressure. Herein, the additional Cosserat kinematical boundary constraints along the bounding surfaces allow a more detailed description of the surface roughness. Specific emphasis is given to the effects of surface roughness as well as the boundary conditions of the entire system on the shear behaviour of layer. According to the obtained results, the shear band location is different in an infinite or finite shear layer depending on the adopted boundary constraints. Further numerical simulations of plane interface shearing are also carried out here using discrete element method (DEM), complementary to Cosserat FE analyses, to better understand the micro-mechanics of granular media near interfaces. FE results are compared with those of experiments as well as DEM simulations and reasonable agreements are seen. The evolution and distribution of state variables and polar quantities in DEM simulations are in proper accordance with the predictions of Cosserat FE model. [ABSTRACT FROM AUTHOR]

Shirin Neshat, an Iranian visual artist, born in Qazvin in 1957 is now living in New York city. Currently, she is working on a film installation in response to September 11.

Recently, the authors have focused on the shear behavior of interface between granular soil body and very rough surface of moving bounding structure. For this purpose, they have used finite element method and a micro-polar elasto-plastic continuum model. They have shown that the boundary conditions assumed along the interface have strong influences on the soil behavior. While in the previous studies, only very rough bounding interfaces have been taken into account, the present investigation focuses on the rough, medium rough and relatively smooth interfaces. In this regard, plane monotonic shearing of an infinite extended narrow granular soil layer is simulated under constant vertical pressure and free dilatancy. The soil layer is located between two parallel rigid boundaries of different surface roughness values. Particular attention is paid to the effect of surface roughness of top and bottom boundaries on the shear behavior of granular soil layer. It is shown that the interaction between roughness of bounding structure surface and the rotation resistance of bounding grains can be modeled in a reasonable manner through considered Cosserat boundary conditions. The influence of surface roughness is investigated on the soil shear strength mobilized along the interface as well as on the location and evolution of shear localization formed within the layer. The obtained numerical results have been qualitatively compared with experimental observations as well as DEM simulations, and acceptable agreement is shown. [ABSTRACT FROM AUTHOR]

Predicting ultimate axial bearing capacity of pile foundations is an important and complicated problem in geotechnical engineering. Cone penetration test (CPT) is a reliableinsitutest widely used in the analysis and design of pile foundations. In this study, new CPT-based axial pile bearing capacity models are presented for both cohesionless and cohesive soils using evolutionary polynomial regression (EPR), a branch of evolutionary approaches. A relatively comprehensive database is gathered and divided into training and testing sub-sets to avoid over-fitting. This database includes both coarse and fine grain soils, cone tip resistance and sleeve friction of CPTs, geometry and bearing capacity of piles. The presented models are compared to some previously published ones and their preferences are demonstrated statistically and probabilistically. Proper applicability of the models in predicting axial pile bearing capacity is then confirmed by field verification, compared to analytical and empirical models available in the literature. [ABSTRACT FROM PUBLISHER]