In situ measurement of root reinforcement using corkscrew extraction method

Gerrit Meijer (Lead / Corresponding author), Anthony Bengough, Jonathan Knappett, Kenneth Loades, Bruce C. Nicoll

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)
526 Downloads (Pure)


Mechanical root reinforcement is an important parameter to evaluate for stability analysis of rooted slopes. The contribution of roots is however difficult to quantify in situ without time-consuming methods or heavy equipment. Here we report field testing using the newly developed “corkscrew” method at two different sites with plantings of conifers and blackcurrant. In both sites we found positive correlations between root quantity and root reinforcement in surface layers where many roots were found. Below 125 mm depth, no correlations could be found, probably due to variability in soil stress and gravel content. Roots were shown not only to increase the soil peak strength, but also to add ductility to the soil, i.e., adding strength over much larger displacement ranges. Measured reinforcement, although similar to other experimental studies, was smaller than predicted using existing models. This may be attributed to the distinct difference in shear displacement required to mobilize the strength of rooted soil as compared with fallow soil. At displacements sufficient to mobilize root strength, the soil strength component has reduced from peak to a much smaller residual strength. The corkscrew method proved a promising tool to quantify root reinforcement in field conditions due to its ease of use and short test duration.

Original languageEnglish
Pages (from-to)1372-1390
Number of pages19
JournalCanadian Geotechnical Journal
Issue number10
Early online date10 Jan 2018
Publication statusPublished - Oct 2018


  • Root-reinforcement
  • cork screw
  • vegetation
  • in situ testing
  • slope stability
  • Root reinforcement
  • In situ testing
  • Vegetation
  • Slope stability
  • Cork screw

ASJC Scopus subject areas

  • Civil and Structural Engineering


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