Vermiculate artefacts in image analysis of granular materials

Sam Stanier*, Jelke Dijkstra, Danuta Leśniewska, James Hambleton, David White, David Muir Wood

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

54 Scopus citations


Some reported analyses of images of deforming granular materials have generated surprising vermiculate strain features which are difficult to reconcile with the mechanics of deformation of granular matter. Detailed investigation using synthetic images and improved processing of images of laboratory experiments indicates that such features can emerge as a consequence of the image acquisition (sensor, contrast, resolution), the subsequent image correlation implementation, and the user's choice of processing parameters. The two principal factors are: (i) the texture and resolution of the images and (ii) the algorithm used to achieve sub-pixel displacement resolution. Analysis of the images using a sub-pixel interpolation algorithm that is more robust than that used originally eliminates the vermiculate features for images with moderate resolution and texture. However, erroneous features persist in images with low resolution and poor texture. Guidance is provided on ways in which such artefacts can be avoided through improved experimental and image analysis techniques.

Original languageEnglish (US)
Pages (from-to)100-113
Number of pages14
JournalComputers and Geotechnics
StatePublished - Feb 1 2016


  • Digital image correlation
  • Granular materials
  • Sub-pixel interpolation
  • Vermiculation

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Computer Science Applications


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