Stochastic Modeling of Relative Permeability for Vegetated Covers
Publication: International Journal of Geomechanics
Volume 18, Issue 9
Abstract
Vegetation induces heterogeneity in the soil porous structure and, hence, relative permeability ( as well. The main objective of this study is to address the uncertainties associated with relative permeability using probabilistic analysis for vegetated covers (i.e., grass and tree species). Bare cover is used as control. For this purpose, the dependence structure of suction, , and volumetric water content,, is established via copula theory, and the curves are predicted with respect to varying levels of suction–volumetric water content correlation. It is found that the of vegetated covers is substantially lower than that in bare covers. The reduction in (with drying) is more in treed cover than grassed cover, since tree roots induce higher levels of suction. Moreover, the air entry value (AEV) of the soil depends on the magnitude of suction–volumetric water content correlation, which, in turn, is influenced by the type of vegetation in the soil. The is highly uncertain in the desaturation zone of the relative permeability curve, which is likely due to inaccuracy of suction measurements beyond 100 kPa. The stochastic behavior of is found to be most significant in treed covers. Finally, a simplified case study is also presented in order to demonstrate the impact of the uncertainty in relative permeability on the stability of vegetates slopes. The factor of safety (FS) is found to vary around 4 to 5% for both bare and vegetated slopes.
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References
Das, G. K., B. Hazra, A. Garg, and C. W. W. Ng. 2017. “Impact of hydrological and mechanical correlations on the reliability of vegetated slopes.” ASCE-ASME J. Risk Uncertainty Eng. Syst., Part A: Civ. Eng. 3 (4): 04017029. https://doi.org/10.1061/AJRUA6.0000934.
Gadi, V. K., S. Bordoloi, A. Garg, Y. Kobayashi, and L. Sahoo. 2016. “Improving and correcting unsaturated soil hydraulic properties with plant parameters for agriculture and bioengineered slopes.” Rhizosphere 1: 58–78. https://doi.org/10.1016/j.rhisph.2016.07.003.
Gadi, V. K., Y.-R. Tang, A. Das, C. Monga, A. Garg, C. Berretta, and L. Sahoo. 2017. “Spatial and temporal variation of hydraulic conductivity and vegetation growth in green infrastructures using infiltrometer and visual technique.” CATENA 155: 20–29. https://doi.org/10.1016/j.catena.2017.02.024.
Garg, A., J. L. Coo, and C. W. W. Ng. 2015a. “Field study on influence of root characteristics on soil suction distribution in slopes vegetated with Cynodon dactylon and Schefflera heptaphylla.” Earth Surf. Processes Landforms 40 (12): 1631–1643. https://doi.org/10.1002/esp.3743.
Garg, A., A. K. Leung, and C. W. W. Ng. 2015b. “Comparisons of soil suction induced by evapotranspiration and transpiration of S. heptaphylla.” Can. Geotech. J. 52 (12): 2149–2155. https://doi.org/10.1139/cgj-2014-0425.
Garg, A., J. Li, J. Hou, C. Berretta, and A. Garg. 2017a. “A new computational approach for estimation of wilting point for green infrastructure.” Meas. 111: 351–358.[ https://doi.org/10.1016/j.measurement.2017.07.026.
Garg, A., and C. W. W. Ng. 2015. “Investigation of soil density effect on suction induced due to root water uptake by Schefflera heptaphylla.” J. Plant Nutr. Soil Sci. 178 (4): 586–591. https://doi.org/10.1002/jpln.201400265.
Garg, A., V. Vijayaraghavan, J. Zhang, and J. S. L. Lam. 2017b. “Robust model design for evaluation of power characteristics of the cleaner energy system.” Renewable Energy 112 302–313. https://doi.org/10.1016/j.renene.2017.05.041.
Garg, A., V. Vijayaraghavan, J. Zhang, S. Li, and X. Liang. 2017c. “Design of robust battery capacity model for electric vehicle by incorporation of uncertainties.” Int. J. Energy Res. 41 (10): 1436–1451. https://doi.org/10.1002/er.3723.
Ghestem, M., R. C. Sidle, and A. Stokes. 2011. “The influence of plant root systems on subsurface flow: implications for slope stability.” BioSci. 61 (11): 869–879. https://doi.org/10.1525/bio.2011.61.11.6.
Hamdhan, I. N., and H. F. Schweiger. 2012. “Finite element method–based analysis of an unsaturated soil slope subjected to rainfall infiltration.” Int. J. Geomech. 13 (5): 653–658. https://doi.org/10.1061/(ASCE)GM.1943-5622.0000239.
Hills, R. G. 1989. “Spatial variability at the Las Cruces Trench site.” In Proceeding of the international workshop on indirect methods for estimating the hydraulic properties of unsaturated soils, 529–538. Riverside.
Huat, B. B., F. H. Ali, and T. H. Low. 2006. “Water infiltration characteristics of unsaturated soil slope and its effect on suction and stability.” Geotech. Geol. Eng. 24 (5): 1293–1306. https://doi.org/10.1007/s10706-005-1881-8.
Leung, A. K., A. Garg, J. L. Coo, C. W. W. Ng, and B. C. H. Hau. 2015a. “Effects of the roots of Cynodon dactylon and Schefflera heptaphylla on water infiltration rate and soil hydraulic conductivity.” Hydrol. Processes 29 (15): 3342–3354. https://doi.org/10.1002/hyp.10452.
Leung, A. K., A. Garg, and C. W. W. Ng. 2015b. “Effects of plant roots on soil-water retention and induced suction in vegetated cover.” Eng. Geol. 193: 183–197. https://doi.org/10.1016/j.enggeo.2015.04.017.
MATLAB. 2015a. MathWorks, Natick, MA.
Mualem, Y. 1976. “A new model for predicting the hydraulic conductivity of unsaturated porous media.” Water Resources Research 12 (3): 513–522.
Ng, C. W. W., V. Kamchoom, and A. K. Leung. 2015. “Centrifuge modelling of the effects of root geometry on transpiration-induced suction and stability of vegetated slopes.” Landslides 13 (5): 925–938. https://doi.org/10.1007/s10346-015-0645-7.
Ng, C. W. W., J. J. Ni, A. K. Leung, and Z. J. Wang. 2016. “A new and simple water retention model for root-permeated soils.” Géotechnique Lett. 6 (1): 106–111. https://doi.org/10.1680/jgele.15.00187.
Phoon, K.-K., A. Santoso, and S.-T. Quek. 2010. “Probabilistic analysis of soil-water characteristic curves.” J. Geotech. Geoenviron. Eng. 136 (3): 445–455. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000222.
Rahimi, A., and H. Rahardjo. 2015. “New approach to improve soil-water characteristic curve to reduce variation in estimation of unsaturated permeability function.” Can. Geotech. J. 53 (4): 717–725. https://doi.org/10.1139/cgj-2015-0199.
van Genuchten, M. T. 1980. “A closed-form equation for predicting the hydraulic conductivity of unsaturated soils.” Soil Sci. Soc. Am. J. 44 (5): 892–898. https://doi.org/10.2136/sssaj1980.03615995004400050002x.
Wu, L. Z., L. M. Zhang, and X. Li. 2015. “One-dimensional coupled infiltration and deformation in unsaturated soils subjected to varying rainfall.” Int. J. Geomech. 16 (2): 06015004. https://doi.org/10.1061/(ASCE)GM.1943-5622.0000535.
Zhang, L. L., D. G. Fredlund, M. D. Fredlund, and G. W. Wilson. 2014. “Modeling the unsaturated soil zone in slope stability analysis 1.” Can. Geotech. J. 51 (12): 1384–1398. https://doi.org/10.1139/cgj-2013-0394.
Zhu, H., and L. M. Zhang. 2015. “Evaluating suction profile in a vegetated slope considering uncertainty in transpiration.” Comput. Geotech. 63: 112–120. https://doi.org/10.1016/j.compgeo.2014.09.003.
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© 2018 American Society of Civil Engineers.
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Received: Jun 8, 2017
Accepted: Apr 10, 2018
Published online: Jun 25, 2018
Published in print: Sep 1, 2018
Discussion open until: Nov 25, 2018
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