Abstract
Purpose
The mechanical contribution of plant roots to the soil shear strength is commonly modelled using fibre bundle models (FBM), accounting for sequential breakage of roots. This study provides a generic framework, able to includes the many different existing approaches, to quantify the effect of various model assumptions.
Methods
The framework uses (1) a single model parameter determining how load is shared between all roots, (2) a continuous power-law distribution of root area ratio over a range of root diameters, and (3) power-law relationships between root diameters and biomechanical properties. A new load sharing parameter, closely resembling how roots mobilise strength under landslide conditions, is proposed. Exact analytical solutions were found for the peak root reinforcement, thus eliminating the current need for iterative algorithms. Model assumptions and results were validated against existing biomechanical and root reinforcement data.
Results
Root reinforcements proved very sensitive to the user-defined load sharing parameter. It is shown that the current method of discretising all roots in discrete diameter classes prior to reinforcement calculations leads to significant overestimations of reinforcement. Addition of a probabilistic distribution of root failure by means of Weibull survival functions, thus adding a second source of sequential mobilisation, further reduced predicted reinforcements, but only when the reduction due to load sharing was limited.
Conclusion
The presented solutions greatly simplify root reinforcement calculations while maintaining analytical exactness as well as clarity in the assumptions made. The proposed standardisation of fibre bundle-type models will greatly aid comparison and exchange of data.
The mechanical contribution of plant roots to the soil shear strength is commonly modelled using fibre bundle models (FBM), accounting for sequential breakage of roots. This study provides a generic framework, able to includes the many different existing approaches, to quantify the effect of various model assumptions.
Methods
The framework uses (1) a single model parameter determining how load is shared between all roots, (2) a continuous power-law distribution of root area ratio over a range of root diameters, and (3) power-law relationships between root diameters and biomechanical properties. A new load sharing parameter, closely resembling how roots mobilise strength under landslide conditions, is proposed. Exact analytical solutions were found for the peak root reinforcement, thus eliminating the current need for iterative algorithms. Model assumptions and results were validated against existing biomechanical and root reinforcement data.
Results
Root reinforcements proved very sensitive to the user-defined load sharing parameter. It is shown that the current method of discretising all roots in discrete diameter classes prior to reinforcement calculations leads to significant overestimations of reinforcement. Addition of a probabilistic distribution of root failure by means of Weibull survival functions, thus adding a second source of sequential mobilisation, further reduced predicted reinforcements, but only when the reduction due to load sharing was limited.
Conclusion
The presented solutions greatly simplify root reinforcement calculations while maintaining analytical exactness as well as clarity in the assumptions made. The proposed standardisation of fibre bundle-type models will greatly aid comparison and exchange of data.
Original language | English |
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Pages (from-to) | 45-65 |
Number of pages | 21 |
Journal | Plant and Soil |
Issue number | 1-2 |
Early online date | 22 Jul 2021 |
DOIs | |
Publication status | Published - 30 Nov 2021 |
Bibliographical note
Funding Information:The author thanks Prof Glyn Bengough (University of Dundee, UK) and Dr Joel Smethurst (University of Southampton, UK) for access to experimental data sets. Further thanks goes to Dr David Boldrin (University of Dundee, UK) for his constructive feedback on the initial submission of this manuscript.
Publisher Copyright:
© 2021, The Author(s).
Keywords
- Fibre bundle model
- Root Bundle Model
- Root cohesion
- Root diameter distributions
- Root reinforcement
- Slope stability
ASJC Scopus subject areas
- Soil Science
- Plant Science
Fingerprint
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GJMeijer/FBMcw
Meijer, G. (Creator), Zenodo, 24 May 2021
DOI: 10.5281/zenodo.4783493, https://github.com/GJMeijer/FBMcw
Dataset