Shear strength anisotropy of rooted soils

Karimzadeh, A. A., Leung, A. K. and Gao, Z. (2022) Shear strength anisotropy of rooted soils. Geotechnique, (doi: 10.1680/jgeot.22.00103) (Early Online Publication)

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Abstract

The shear strength of rooted soils depends on the principal stress direction owing to the anisotropy in soil structure and root system. Existing failure criteria cannot describe the strength anisotropy of rooted soils under general loading conditions because they are mainly based on the test results of direct shear. This study presents a new generalised 3-D anisotropic failure criterion for rooted soils. The model employs the projection of two independent microstructure fabric tensors (soil fabric and root network) on the stress tensor. Twenty-four drained triaxial compression and extension tests were carried out to measure the strength anisotropy of silty sand vegetated with vetiver grass (Chrysopogon zizanioides L.) at different overconsolidation ratios and calibrate the material parameters for the proposed criterion. Anisotropies of both cohesion and friction angle exist in rooted soil. Roots contribute mainly to the increase in cohesion (hence root cohesion) from most of the direct shear test data. Roots with predominant orientation aligning in the tensile strain direction contribute the most to soil strength. In the case of vetiver grass, which has a taproot system, their roots show the strongest reinforcement effect in conventional triaxial extension path, in which the maximum portion of roots are subjected to tension.

Item Type:Articles
Additional Information:The authors acknowledge the financial support provided by the General Research Fund (Grants 16212818, 16202720), the Collaborative Research Fund (Grant C6006-20G) funded by the Hong Kong Research Grants Council and the grant from the National Natural Science Foundation of China (Grant 51922112)
Status:Early Online Publication
Refereed:Yes
Glasgow Author(s) Enlighten ID:Gao, Dr Zhiwei
Authors: Karimzadeh, A. A., Leung, A. K., and Gao, Z.
College/School:College of Science and Engineering > School of Engineering > Infrastructure and Environment
Journal Name:Geotechnique
Publisher:ICE Publishing
ISSN:0016-8505
ISSN (Online):1751-7656
Published Online:20 September 2022
Copyright Holders:Copyright © ICE Publishing
First Published:First published in Geotechnique 2022
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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