A microstructure-based finite element analysis of the response of sand

Nadimi, S., Fonseca, J. & Taylor, N. (2015). A microstructure-based finite element analysis of the response of sand. Paper presented at the Sixth International Symposium on Deformation Characteristics of Geomaterials, 15-11-2015 - 18-11-2015, Buenos Aires.

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Abstract

This paper presents a novel contribution towards understanding the stress distribution amongst the constituent grains of an intact sand under loading. Photoelasticity using birefringent materials has shown that forces in granular media are transmitted from particle-to-particle via their contacts and the mode of load propagation forms a complex force network. Particles carrying above average load appear to form a network with special characteristics where stronger forces are carried through chain-like particle groups, often referred as force chains. Fonseca et al. (2013) showed that for a sand under shearing, the contact normals tend to be orientated along the direction of the major principal stress, which suggests the formation of force chains. Moreover, these quasi-vertically oriented vectors were shown to be associated with contacts having large surface areas, contributing to the formation of solid columnar structures of stress transmitting grains. This early study demonstrates that a full characterization of force chains for real soils requires accounting for the effects of the soil microstructure, including grain morphology and contact topology, which the idealized nature of the particles used for discrete element method simulations and photoelasticity studies cannot capture. In the present work, high resolution x-ray tomographic data of an intact sand is converted into a two dimensional finite element mesh, so that the microstructural details, such as the geometrical arrangement of the grains and pores, as well as grain shape and contact topology are incorporated in the model. In other words, the soil microstructure is modelled using a computation approach that considers all available geometrical data. The results suggested that the ability of the grains to transmit stress via their contacts is directly associated to the degrees of freedom they have to move and rearrange, which in turn is controlled by the topology of the contacts. The insights into the effects of microstructure on the stress transmission mechanisms provided in this study are fundamental to better understand and predict the macro scale response of soil.

Item Type: Conference or Workshop Item (Paper)
Additional Information: Advances in Soil Mechanics and Geotechnical Engineering, Volume 6: Deformation Characteristics of Geomaterials, Victor A. Rinaldi, Marcelo E. Zeballos, Juan Jose Clariá (eds), A microstructure-based finite element analysis of the response of sand, 816-823, Copyright 2015, with permission from IOS Press.
Uncontrolled Keywords: Fabric/microstructure of soil, image, sand, µFE, finite element modelling
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Divisions: School of Engineering & Mathematical Sciences > Engineering
Related URLs:
URI: http://openaccess.city.ac.uk/id/eprint/13010

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