Root reinforcement: analyses and experiments

Wu, Tien H.

doi:10.1007/978-1-4020-5593-5_3

Cited by 21 publications

(7 citation statements)

References 23 publications

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“… Wu et al 's [1979] approach is widely used as it incorporates data on root and soil mechanical properties in an easy‐to‐apply model. A limiting assumption in Wu et al 's [1979] model is that all roots break simultaneously which is not supported by observations [ Pollen et al , 2004; Wu , 2007; Fan and Su , 2008] and results in a consistent overprediction of actual root reinforcement function. Early models typically did not consider geometrical and stress‐strain behavior of root bundles, a necessary element for describing complex interactions between roots and soil matrix.…”

Section: Introductionmentioning

confidence: 98%

Root‐soil mechanical interactions during pullout and failure of root bundles

2010

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[1] Roots play a major role in reinforcing and stabilizing steep hillslopes. Most studies in slope stability implement root reinforcement as an apparent cohesion by upscaling the behavior of static individual roots. Recent studies, however, have shown that much better predictions of slope stability can be made if the progressive failure of bundles of roots are considered. The characteristics of progressive failure depend on interactions between soil deformation and root bundle geometric and mechanical properties. We present a detailed model for the quantitative description of the mechanical behavior of a bundle of roots under strain-controlled mechanical forcing. The Root Bundle Model explicitly considers typical values of root-size spatial distribution (number and dimension of roots), geometric factors (diameter-length proportion, tortuosity, and branching characteristics), and mechanical characteristics (tensile strength and Young's modulus) and interactions under various soil conditions (soil type, confining pressure, and soil moisture). We provide systematic analyses of the roles of these factors on the mechanical response of the bundle and explore the relative importance of various parameters to the macroscopic root-soil mechanical response. We distinguish between increased strength imparted by small roots at small deformations and the resilience imparted by larger roots to the growth of large tensile cracks, showing that the maximal reinforcement of fine roots is reached within the first 5 cm of displacement whereas a root of 20 mm diameter may reach its maximal pullout force after 10 cm displacement. The model reproduces the gradual straining and ultimate residual failure behavior of root systems often observed in hillslopes, with progressive growth of tension cracks improving estimations of root reinforcement when considering the effects of root distribution and the variation of the pullout force as a function of displacement. These results enhance understanding of root reinforcement mechanisms and enable more realistic implementation of root reinforcement modeling for stability calculations of vegetated slopes and for guiding ongoing experimental efforts to gather critical root-soil mechanical information.Citation: Schwarz, M., D. Cohen, and D. Or (2010), Root-soil mechanical interactions during pullout and failure of root bundles,

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Section: Introductionmentioning

confidence: 98%

Root‐soil mechanical interactions during pullout and failure of root bundles

2010

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“…This range of depths was chosen according to [7] as, 'maximum depth of roots of grass and forbs in temperate zones is usually no greater than 0.5'. Therefore below this depth any slip plane will be subject to the shear apparent cohesion and peak angle of friction of the soil alone; Density of water, γ w = 9.81kN/m 3 ; Height of water table, h = 0.5m -This was chosen as a worst case scenario to give the lowest F.O.S.…”

Section: Slope Fos For Unrooted Soilmentioning

confidence: 99%

Enhancing Slope Stability With Vegetation

Hytiris¹

2015

geomate

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Landslides can have serious impact on natural and human environment and their prevention and mitigation is of global concern. The ability of a slope to resist a landslide depends on the materials and the properties of which it is composed. This project focuses on the increased landslide resistance of a slope due to vegetation. The properties of the soil-root composite were measured in laboratory and, from these results, calculation and graphically based evaluation was used to determine their qualities for resisting landslide. The results show that vegetation roots had a stabilising effect on the slope, limited to the rooting depth. Knowing the rooting depth (generally between 0.5 and 1.5 m) and dependent on the species, a correlation between the ratio of root weight to soil weight and the slope ability to resist landslide was implied from experimental results and a hypothetical design chart and equation were derived.

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“…A good compromise between the WWM type of models and finite element analyses is the use of Winkler beam‐spring‐supported models. These have been suggested and applied for roots in the past,() although the axial loading component was either ignored or set to a constant value, so that an analytical solution could be found for the Euler‐Bernoulli differential equation for beam bending:

E I \frac{d^{4} w}{normald x^{4}} = q_{l} + N \frac{d^{2} w}{normald x^{2}},

where E I is the elastic bending stiffness, and w is the transverse displacement along the root axis x . q l is a transverse loading term, and N is the axial force (assumed constant) in the root.…”

Section: Introductionmentioning

confidence: 99%

Analysis of coupled axial and lateral deformation of roots in soil

Meijer

Wood

Knappett

et al. 2018

Num Anal Meth Geomechanics

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Summary Plant roots can help to stabilise slopes. Existing analytical models to predict their mechanical contribution are however limited: they typically focus on the ultimate limit state, employ various empirical factors, and ignore much of the underlying root‐soil interaction. A new model was developed based on large deflection Euler‐Bernoulli elastic beam theory that can be used to study the mobilisation of root strength under various loading conditions (direct shear and pull‐out). Both lateral and axial loading of the root by the soil were incorporated, based on existing methodologies for foundation piles (p‐y and t‐z curves). The model is able to take the key parameters into account (root biomechanical properties, root architectural properties, and soil properties) while remaining quick to solve using a numerical boundary value problem solver. The model was compared with experimental direct shear test data using various root analogues (rubber, plastic, and wood) in dry sand with various densities and effective stress levels and was able to accurately predict the measured shear force‐displacement behaviour. Comparison with experimentally measured pull‐out force‐displacement curves using rubber and wooden root analogues with various architectures in dry and partially saturated sands was also satisfactory. In the future, this model can aid with addressing long‐standing problems in the root‐reinforcement community: quantifying the effect of (sequential) mobilisation of root strength in direct shear, the effect of the angle at which the root crosses a shear plane, the effect of root topology on root‐reinforcement or the effect of root bending, and root shear shear forces on root‐reinforcement.

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Root reinforcement: analyses and experiments

Cited by 21 publications

References 23 publications

Root‐soil mechanical interactions during pullout and failure of root bundles

Root‐soil mechanical interactions during pullout and failure of root bundles

Enhancing Slope Stability With Vegetation

Analysis of coupled axial and lateral deformation of roots in soil

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