Root size effects on transverse root-soil interactions

X. Zhang, J. A. Knappett (Lead / Corresponding author), M. O. Ciantia, A. K. Leung, H. Wang, T. Liang

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For smaller lateral plant roots in coarse-grained soils, a potentially large relative size of soil particles compared to the roots may affect their transverse resistance. Even for the larger roots of trees, particle size effects may be important, e.g. when testing 1:N reduced scale models in a geotechnical centrifuge. The Discrete Element Method (DEM) was used to investigate this problem. A rigid lateral root segment under transverse loading in plane strain was simulated and compared with Finite Element Method (FEM) simulations, where the soil was modelled as a continuum (no particle size effects). Even at the lower root/particle diameter ratios (dr/D50) investigated (6 to 21), particle size effects on transverse capacity were negligible upon push-in, while during uplift, they were observed for (dr/D50) <8, arising from the dimension of the uplifted soil volume above the root. The material properties of roots are also typically diameter dependent. Further simulations of long flexible roots subject to end rotation were performed employing a beam-on-non-linear-Winkler-foundation approach, using p-y curves obtained from the DEM or FEM simulations. Compared with particle-size related effects, diameter-dependent variation of material properties had a much larger controlling effect on root capacity and stiffness as relevant for plant/tree overturning.
Original languageEnglish
Article number105860
Number of pages12
JournalComputers and Geotechnics
Early online date24 Oct 2023
Publication statusPublished - Jan 2024


  • Vegetation
  • Root-soil interaction
  • Distinct Element Method
  • Size effects
  • Sand

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Computer Science Applications


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