A critical evaluation of predictive models for rooted soil strength with application to predicting the seismic deformation of rooted slopes

Teng Liang, Jonathan Adam Knappett (Lead / Corresponding author), Anthony Leung, Andrew Carnaghan, Glyn Bengough, Rui Zhao

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Abstract

This paper presents a comparative study of three different classes of model for estimating the reinforcing effect of plant roots in soil, namely: (i) fibre pull out model, (ii) fibre break models (including Wu and Waldron’s Model (WWM) and the Fibre Bundle Model (FBM)) and (iii) beam bending or p-y models (specifically Beam on a Non-linear Winkler-Foundation (BNWF) models). Firstly, the prediction model of root reinforcement based on pull-out being the dominant mechanism for different potential slip plane depths was proposed. The resulting root reinforcement calculated were then compared with those derived from the other two types of models. The estimated rooted soil strength distributions were then incorporated within a fully dynamic, plane-strain continuum Finite-Element model to assess the consequences of the selection of rooted soil strength model on the global seismic stability of a vegetated slope (assessed via accumulated slip during earthquake shaking). For the particular case considered in this paper (no roots were observed to have broken after shearing), root cohesion predicted by the pull out model is much closer to that the BNWF model, but is largely overpredicted by the family of fibre break models. In terms of the effects on the stability of vegetated slopes, there exists a threshold value beyond which the position of the critical slip plane would bypass the rooted zones, rather than passing through them. Further increase of root cohesion beyond this value has minimal effect on the global slope behaviour. This implies that significantly over-predicted root cohesion from fibre break models when used to model roots with non-negligible bending stiffness may still provide a reasonable prediction of overall behaviour, so long as the critical failure mechanism is already bypassing the root-reinforced zones.
Original languageEnglish
Number of pages17
JournalLandslides
Early online date22 Aug 2019
DOIs
Publication statusE-pub ahead of print - 22 Aug 2019

Fingerprint

soil strength
Soils
Winkler foundation
cohesion
Fibers
evaluation
reinforcement
Reinforcement
plane strain
failure mechanism
bypass
prediction
Shearing

Keywords

  • Earthquakes
  • Finite element model
  • Pull-out resistance
  • Root reinforcement
  • Slope stability
  • Uprooting
  • Vegetation

Cite this

@article{832695e8073b4dd28b1e54626e56e273,
title = "A critical evaluation of predictive models for rooted soil strength with application to predicting the seismic deformation of rooted slopes",
abstract = "This paper presents a comparative study of three different classes of model for estimating the reinforcing effect of plant roots in soil, namely: (i) fibre pull out model, (ii) fibre break models (including Wu and Waldron’s Model (WWM) and the Fibre Bundle Model (FBM)) and (iii) beam bending or p-y models (specifically Beam on a Non-linear Winkler-Foundation (BNWF) models). Firstly, the prediction model of root reinforcement based on pull-out being the dominant mechanism for different potential slip plane depths was proposed. The resulting root reinforcement calculated were then compared with those derived from the other two types of models. The estimated rooted soil strength distributions were then incorporated within a fully dynamic, plane-strain continuum Finite-Element model to assess the consequences of the selection of rooted soil strength model on the global seismic stability of a vegetated slope (assessed via accumulated slip during earthquake shaking). For the particular case considered in this paper (no roots were observed to have broken after shearing), root cohesion predicted by the pull out model is much closer to that the BNWF model, but is largely overpredicted by the family of fibre break models. In terms of the effects on the stability of vegetated slopes, there exists a threshold value beyond which the position of the critical slip plane would bypass the rooted zones, rather than passing through them. Further increase of root cohesion beyond this value has minimal effect on the global slope behaviour. This implies that significantly over-predicted root cohesion from fibre break models when used to model roots with non-negligible bending stiffness may still provide a reasonable prediction of overall behaviour, so long as the critical failure mechanism is already bypassing the root-reinforced zones.",
keywords = "Earthquakes, Finite element model, Pull-out resistance, Root reinforcement, Slope stability, Uprooting, Vegetation",
author = "Teng Liang and Knappett, {Jonathan Adam} and Anthony Leung and Andrew Carnaghan and Glyn Bengough and Rui Zhao",
note = "China Sponsorship Council Grant number 2011637138",
year = "2019",
month = "8",
day = "22",
doi = "10.1007/s10346-019-01259-8",
language = "English",
journal = "Landslides",
issn = "1612-510X",
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T1 - A critical evaluation of predictive models for rooted soil strength with application to predicting the seismic deformation of rooted slopes

AU - Liang, Teng

AU - Knappett, Jonathan Adam

AU - Leung, Anthony

AU - Carnaghan, Andrew

AU - Bengough, Glyn

AU - Zhao, Rui

N1 - China Sponsorship Council Grant number 2011637138

PY - 2019/8/22

Y1 - 2019/8/22

N2 - This paper presents a comparative study of three different classes of model for estimating the reinforcing effect of plant roots in soil, namely: (i) fibre pull out model, (ii) fibre break models (including Wu and Waldron’s Model (WWM) and the Fibre Bundle Model (FBM)) and (iii) beam bending or p-y models (specifically Beam on a Non-linear Winkler-Foundation (BNWF) models). Firstly, the prediction model of root reinforcement based on pull-out being the dominant mechanism for different potential slip plane depths was proposed. The resulting root reinforcement calculated were then compared with those derived from the other two types of models. The estimated rooted soil strength distributions were then incorporated within a fully dynamic, plane-strain continuum Finite-Element model to assess the consequences of the selection of rooted soil strength model on the global seismic stability of a vegetated slope (assessed via accumulated slip during earthquake shaking). For the particular case considered in this paper (no roots were observed to have broken after shearing), root cohesion predicted by the pull out model is much closer to that the BNWF model, but is largely overpredicted by the family of fibre break models. In terms of the effects on the stability of vegetated slopes, there exists a threshold value beyond which the position of the critical slip plane would bypass the rooted zones, rather than passing through them. Further increase of root cohesion beyond this value has minimal effect on the global slope behaviour. This implies that significantly over-predicted root cohesion from fibre break models when used to model roots with non-negligible bending stiffness may still provide a reasonable prediction of overall behaviour, so long as the critical failure mechanism is already bypassing the root-reinforced zones.

AB - This paper presents a comparative study of three different classes of model for estimating the reinforcing effect of plant roots in soil, namely: (i) fibre pull out model, (ii) fibre break models (including Wu and Waldron’s Model (WWM) and the Fibre Bundle Model (FBM)) and (iii) beam bending or p-y models (specifically Beam on a Non-linear Winkler-Foundation (BNWF) models). Firstly, the prediction model of root reinforcement based on pull-out being the dominant mechanism for different potential slip plane depths was proposed. The resulting root reinforcement calculated were then compared with those derived from the other two types of models. The estimated rooted soil strength distributions were then incorporated within a fully dynamic, plane-strain continuum Finite-Element model to assess the consequences of the selection of rooted soil strength model on the global seismic stability of a vegetated slope (assessed via accumulated slip during earthquake shaking). For the particular case considered in this paper (no roots were observed to have broken after shearing), root cohesion predicted by the pull out model is much closer to that the BNWF model, but is largely overpredicted by the family of fibre break models. In terms of the effects on the stability of vegetated slopes, there exists a threshold value beyond which the position of the critical slip plane would bypass the rooted zones, rather than passing through them. Further increase of root cohesion beyond this value has minimal effect on the global slope behaviour. This implies that significantly over-predicted root cohesion from fibre break models when used to model roots with non-negligible bending stiffness may still provide a reasonable prediction of overall behaviour, so long as the critical failure mechanism is already bypassing the root-reinforced zones.

KW - Earthquakes

KW - Finite element model

KW - Pull-out resistance

KW - Root reinforcement

KW - Slope stability

KW - Uprooting

KW - Vegetation

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U2 - 10.1007/s10346-019-01259-8

DO - 10.1007/s10346-019-01259-8

M3 - Article

JO - Landslides

JF - Landslides

SN - 1612-510X

ER -