Evaluating suction profile in a vegetated slope considering uncertainty in transpiration

Zhu, Hong; Zhang, Li Min

doi:10.1016/j.compgeo.2014.09.003

Cited by 49 publications

(15 citation statements)

References 37 publications

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“…Zhu and Zhang (2015) also got similar results by numerical simulations, they found different root architectures show little difference in retaining suction at the end of rainfall. In addition.…”

Section: Influence Of Root Architecture For Rainfall On Pwp Distributsupporting

confidence: 84%

“…Feddes et al (1978), Prasad (1988) and Raats (1974) examined the effect of root water uptake on water content distributions rather than PWP distributions in the root zone in flat ground. Recently, Zhu and Zhang (2015) carried out numerical study on PWP distributions in a finite vegetated slope subjected to rainfall, considering two root architectures (uniform and triangular) and focusing on the uncertainty in transpiration rate, however, root architecture's effect at drying condition has not been given due emphasis. Yuan and Lu (2005) provided analytical solutions for calculating 1D water flow and volumetric water content in unsaturated flat ground with roots under time-dependent surface flux.…”

Section: Introductionmentioning

confidence: 99%

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Analytical solutions for calculating pore-water pressure in an infinite unsaturated slope with different root architectures

Liu

Feng

2015

Can. Geotech. J.

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Vegetation can reduce pore water pressure in soil by root water uptake. The reduction of pore water pressure results in higher shear strength but lower water permeability of soil, affecting slope stability and rainfall infiltration, respectively. Effects of different root architectures on root water uptake and hence pore water pressure distributions are not well understood. In this study, new analytical solutions for calculating pore water pressure in an infinite unsaturated vegetated slope are derived for different root architectures, namely the uniform, triangular, exponential and parabolic root architectures. Using the newly developed solutions, four series of analytical parametric analyses are carried out to improve understanding of the factors affecting root water uptake and hence that influence pore water pressure distributions. In the dry season, different root architectures can lead to large variations in pore water pressure distributions. It is found that the exponential root architecture induces the highest negative pore water pressure in the soil, followed by the triangular, uniform and parabolic root architectures. The maximum pore water pressure induced by the parabolic root architecture is about 77% of that induced by the exponential root architecture at the steady state. For a given root architecture, vegetation in completely decomposed granite (CDG, classified as silty sand) induces the highest negative pore water pressure than that in fine sand and silt. The zone influenced by vegetation can be about three to six times the root depth. In wet season, after a ten-year return period rainfall with a duration of 24 hours, different root architectures show similar pore water pressure distributions.

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Section: Influence Of Root Architecture For Rainfall On Pwp Distributsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Analytical solutions for calculating pore-water pressure in an infinite unsaturated slope with different root architectures

Liu

Feng

2015

Can. Geotech. J.

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“…This is because both the processes are non-linear and are a direct function of suction (Wilson et al 1994;Feddes et al 1978;Cui et al 2013). Also, in addition to LAI, Root area index (RAI; a dimensionless index normalising total root surface area for a given root depth by plan cross-section area of soil) is known to influence soil moisture/suction profiles (López et al 2001;Zhu and Zhang, 2015). RAI signifies the ability of water uptake by fine roots within the root zone.…”

Section: Introductionmentioning

confidence: 99%

Comparisons of soil suction induced by evapotranspiration and transpiration ofS. heptaphylla

Garg

Leung

2015

Can. Geotech. J.

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For a given evapotranspiration (ETr), both soil evaporation and plant transpiration (Tr) would induce soil suction. However, the relative contribution of these two processes to the amount of suction induced is not clear. The objective of this study is to quantify ETr- and Tr-induced suction by a selected tree species, Scheffllera heptaphylla, in silty sand. The relative contribution of transpiration and evaporation to the responses of suction is then explored based on observed differences in Tr- and ETr-induced suction. In total, 12 test boxes were used for testing: 10 for vegetated soil with different values of leaf area index (LAI) and root area index (RAI), while two were for bare soil as references. Each box was exposed to identical atmospheric conditions controlled in a plant room for monitoring suction responses over a week. Due to the additional effects of soil evaporation, ETr-induced suction could be 3%–47% higher than Tr-induced suction, depending on LAI. The significance of evaporation reduced substantially when LAI was higher, as relatively less radiant energy fell on the soil surface for evaporation. For a given LAI, the effects of evaporation were less significant at deeper depths within the root zone. The effects of RAI associated with root-water uptake upon transpiration were the dominant process of ETr affecting the suction responses.

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“…Further investigations could tackle this issue and consider the variability of root systems in different soil environments and incorporate hydrological impacts of root systems on the soil, e.g. by root water uptake (Zhu and Zhang 2015). Based on the results of this study, we highlight that the spatial distribution of cohesion values within the approximated root system should be favoured compared to uniform cohesion values.…”

Section: Separated Vs Mixed Standsmentioning

confidence: 99%

Integration of root systems into a GIS-based slip surface model: computational experiments in a generic hillslope environment

Schmaltz

Mergili

2018

Landslides

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Integration of root systems into a GIS-based slip surface model: computational experiments in a generic hillslope environment Abstract Root systems of trees reinforce the underlying soil in hillslope environments and therefore potentially increase slope stability. So far, the influence of root systems is disregarded in Geographic Information System (GIS) models that calculate slope stability along distinct failure plane. In this study, we analyse the impact of different root system compositions and densities on slope stability conditions computed by a GIS-based slip surface model. We apply the 2.5D slip surface model r.slope.stability to 23 root system scenarios imposed on pyramidoid-shaped elements of a generic landscape. Shallow, taproot and mixed root systems are approximated by paraboloids and different stand and patch densities are considered. The slope failure probability (P f ) is derived for each raster cell of the generic landscape, considering the reinforcement through root cohesion. Average and standard deviation of P f are analysed for each scenario. As expected, the r.slope.stability yields the highest values of P f for the scenario without roots. In contrast, homogeneous stands with taproot or mixed root systems yield the lowest values of P f . P f generally decreases with increasing stand density, whereby stand density appears to exert a more pronounced influence on P f than patch density. For patchy stands, P f increases with a decreasing size of the tested slip surfaces. The patterns yielded by the computational experiments are largely in line with the results of previous studies. This approach provides an innovative and simple strategy to approximate the additional cohesion supplied by root systems and thereby considers various compositions of forest stands in 2.5D slip surface models. Our findings will be useful for developing strategies towards appropriately parameterising root reinforcement in real-world slope stability modelling campaigns.

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Evaluating suction profile in a vegetated slope considering uncertainty in transpiration

Cited by 49 publications

References 37 publications

Analytical solutions for calculating pore-water pressure in an infinite unsaturated slope with different root architectures

Analytical solutions for calculating pore-water pressure in an infinite unsaturated slope with different root architectures

Comparisons of soil suction induced by evapotranspiration and transpiration ofS. heptaphylla

Integration of root systems into a GIS-based slip surface model: computational experiments in a generic hillslope environment

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