Modelling of stress transfer in root-reinforced soils informed by four-dimensional X-ray computed tomography and digital volume correlation data

TY - JOUR

T1 - Modelling of stress transfer in root-reinforced soils informed by four-dimensional X-ray computed tomography and digital volume correlation data

AU - Bull, Daniel J.

AU - Smethurst, Joel A.

AU - Meijer, Gerrit J.

AU - Sinclair, I.

AU - Pierron, Fabrice

AU - Roose, Tiina

AU - Powrie, William

AU - Bengough, A. Glyn

N1 - Funding Information: This research was funded by the UK Engineering and Physical Sciences Research Council grant nos EP/M020177/1 and EP/M020355/1, as part of a collaboration between the University of Southampton, University of Dundee, University of Aberdeen, Durham University and the James Hutton Institute. The James Hutton Institute receives funding from the Scottish Government (Rural & Environmental Services & Analytical Services Division). The authors acknowledge the µ-VIS X-ray Imaging Centre at the University of Southampton for provision of tomographic imaging facilities, supported by EPSRC grant no. EP/H01506X. Acknowledgements. Dr Sonja Schmidt carried out the initial development work on the shear rig, with technical support from Harvey Skinner and Karl Scammell. Publisher Copyright: © 2022 The Authors.

PY - 2022/1/26

Y1 - 2022/1/26

N2 - Vegetation enhances soil shearing resistance through water uptake and root reinforcement. Analytical models for soils reinforced with roots rely on input parameters that are difficult to measure, leading to widely varying predictions of behaviour. The opaque heterogeneous nature of rooted soils results in complex soil-root interaction mechanisms that cannot easily be quantified. The authors measured, for the first time, the shear resistance and deformations of fallow, willow-rooted and gorse-rooted soils during direct shear using X-ray computed tomography and digital volume correlation. Both species caused an increase in shear zone thickness, both initially and as shear progressed. Shear zone thickness peaked at up to 35 mm, often close to the thickest roots and towards the centre of the column. Root extension during shear was 10-30% less than the tri-linear root profile assumed in a Waldron-type model, owing to root curvature. Root analogues used to explore the root-soil interface behaviour suggested that root lateral branches play an important role in anchoring the roots. The Waldron-type model was modified to incorporate non-uniform shear zone thickness and growth, and accurately predicted the observed, up to sevenfold, increase in shear resistance of root-reinforced soil.

AB - Vegetation enhances soil shearing resistance through water uptake and root reinforcement. Analytical models for soils reinforced with roots rely on input parameters that are difficult to measure, leading to widely varying predictions of behaviour. The opaque heterogeneous nature of rooted soils results in complex soil-root interaction mechanisms that cannot easily be quantified. The authors measured, for the first time, the shear resistance and deformations of fallow, willow-rooted and gorse-rooted soils during direct shear using X-ray computed tomography and digital volume correlation. Both species caused an increase in shear zone thickness, both initially and as shear progressed. Shear zone thickness peaked at up to 35 mm, often close to the thickest roots and towards the centre of the column. Root extension during shear was 10-30% less than the tri-linear root profile assumed in a Waldron-type model, owing to root curvature. Root analogues used to explore the root-soil interface behaviour suggested that root lateral branches play an important role in anchoring the roots. The Waldron-type model was modified to incorporate non-uniform shear zone thickness and growth, and accurately predicted the observed, up to sevenfold, increase in shear resistance of root-reinforced soil.

KW - Direct shear

KW - X-ray computed tomography

KW - digital volume correlation

KW - root reinforcement

KW - shear zone thickness

KW - slope stability

UR - https://www.scopus.com/pages/publications/85126926382

U2 - 10.1098/rspa.2021.0210

DO - 10.1098/rspa.2021.0210

M3 - Article

C2 - 35153607

SN - 1364-5021

VL - 478

JO - Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences

JF - Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences

IS - 2257

M1 - 20210210

ER -