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Image-based investigation into the primary fabric of stress-transmitting particles in sand

Fonseca, J; Nadimi, S; Reyes-Aldasoro, CC; O'Sullivan, C; Coop, MR; (2016) Image-based investigation into the primary fabric of stress-transmitting particles in sand. Soils and Foundations , 56 (5) pp. 818-834. 10.1016/j.sandf.2016.08.007. Green open access

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Abstract

This paper uses three-dimensional images of a natural silica sand to analyse the mechanisms of stress transmission under triaxial compression. As discussed in Fonseca, J., O’Sullivan, C., Coop, M., Lee, P.D., (2012), the irregular morphology and locked fabric that can be found in natural sands lead to the formation of contacts with extended surface areas. However, most of our current understanding of stress-transmission phenomena comes from DEM simulations and photo-elastic experiments using idealised grain shapes and contact topologies. The direct measurement of stress transmission in assemblies of real soil grains is a challenging task. The present study postulates that important insight can be obtained by following the evolution of intergranular contacts as the grains rearrange and by considering how these rearrangements enhance the stability of the material. The methodology consists of measuring the geometrical data of the individual grains and their associated contacts obtained at successive load stages in the post-peak regime (after shear band formation). A statistical analysis of the vectors normal to the contacts reveals a realignment of these vectors in the direction of the major principal stress; this is a clear indication of the formation of force chains. A subsequent analysis shows that these columnar structures of stress-transmitting grains are associated with larger contact surfaces and have distinct patterns in the regions affected by the formation of a shear band. An algorithm based on stability and load-transmission criteria is developed to contribute new insight into the characterisation of load-bearing sand particles.

Type: Article
Title: Image-based investigation into the primary fabric of stress-transmitting particles in sand
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.sandf.2016.08.007
Publisher version: http://dx.doi.org/10.1016/j.sandf.2016.08.007
Language: English
Additional information: Copyright © 2016. This manuscript version is published under a Creative Commons Attribution Non-commercial Non-derivative 4.0 International licence (CC BY-NC-ND 4.0). This licence allows you to share, copy, distribute and transmit the work for personal and non-commercial use providing author and publisher attribution is clearly stated. Further details about CC BY licences are available at http://creativecommons.org/licenses/by/4.0. Access may be initially restricted by the publisher.
Keywords: Fabric/structure of soils; 3D microscopy; Shearing; Locked sand; Stress-transmission
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Civil, Environ and Geomatic Eng
URI: https://discovery.ucl.ac.uk/id/eprint/1525594
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