Impact of Hydrological and Mechanical Correlations on the Reliability of Vegetated Slopes
Publication: ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part A: Civil Engineering
Volume 3, Issue 4
Abstract
Vegetation enhances the strength characteristics of soil by inducing suction in soil through root water uptake. This in turn affects the stability of a wide variety of geotechnical structures, including slopes. In order to properly assess the stability of vegetated slopes, it is essential to address the hydrological (suction, , and volumetric water content, ) and mechanical (cohesion, , and angle of internal friction, ) properties of vegetated soil. Both hydrological and mechanical parameters share negative correlations among each other, by virtue of which the stability of vegetated slopes is significantly affected. This study addresses the individual and combined effects of both and correlations on the reliability of vegetated slopes in a probabilistic framework. The aforementioned dependencies are incorporated utilizing copula theory, which establishes a unique relationship between the individual bivariate density functions and their respective marginal distributions. The bivariate data of the aforementioned hydrological and mechanical parameters are obtained from a field monitoring program conducted on a homogeneously compacted vegetated slope. To better comprehend the unsaturated behavior of vegetated slopes, the effect of correlation on the soil water characteristic curve (SWCC) of vegetated soil is established. It is found that vegetation induces uncertainties in parameters to a greater extent than does correlation. The randomness induced by vegetation is found to be more in the saturation zone than in the desaturation zone. Moreover, the impact of mechanical correlations on slope stability is found to be more significant than that of hydrological correlation.
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Acknowledgments
The third author of this manuscript acknowledges the support of Shantou University Scientific Research Fund (NTF17007). The fourth author would like to acknowledge Research Grants Council (RGC) grants (T22-603/15N and HKUST6/CRF/12R) for support.
References
Ali, A., et al. (2014). “Simplified quantitative risk assessment of rainfall-induced landslides modelled by infinite slopes.” Eng. Geol., 179, 102–116.
Barker, D. H. (1995). “The way ahead-continuing and future developments in vegetative slope engineering or ecoengineering.” Vegetation and slopes: Stabilization, protection and ecology, Institution of Civil Engineers, London, 238–255.
Benson, C. H., Chiang, I., Chalermyanont, T., and Sawangsuriya, A. (2014). “Estimating van Genuchten parameters α and n for clean sands from particle size distribution data.” Geo-Congress 2014, ASCE, Reston, VA, 234–235.
Brooks, R. H., and Corey, A. T. (1964). “Hydraulic properties of porous media.”, Colorado State Univ., Fort Collins, CO.
Calo, E., Sako, K., Araki, K., Miyamoto, Y., and Kitamura, R. (2011). “A probabilistic and mechanical approach for hysteresis of SWCC in unsaturated soil.” Geo-Frontiers 2011: Advances in Geotechnical Engineering, ASCE, Reston, VA, 3887–3895.
Chen, L., Huang, Z., Gong, J., Fu, B., and Huang, Y. (2007). “The effect of land cover/vegetation on soil water dynamic in the hilly area of the loess plateau, China.” Catena, 70(2), 200–208.
Chirico, G. B., Borga, M., Tarolli, P., Rigon, R., and Preti, F. (2013). “Role of vegetation on slope stability under transient unsaturated conditions.” Procedia Environ. Sci., 19, 932–941.
Chiu, C. F., Yan, W. M., and Yuen, K. V. (2012). “Reliability analysis of soil–water characteristics curve and its application to slope stability analysis.” Eng. Geol., 135, 83–91.
Collison, A., and Simon, A. (2001). “Beyond root reinforcement: The hydrologic effects of riparian vegetation on riverbank stability.” Wetlands Engineering and River Restoration 2001, ASCE, Reston, VA, 1–12.
Das, G. K., Hazra, B., Garg, A., Ng, C. W. W., Lateh, H., and Nazi, A. (2017). “Bivariate probabilistic modelling of hydro-mechanical properties of vegetated soils.” Adv. Civil Eng. Mater., 6(1), 235–257.
Dou, H. Q., Han, T. C., Gong, X. N., and Zhang, J. (2014). “Probabilistic slope stability analysis considering the variability of hydraulic conductivity under rainfall infiltration–redistribution conditions.” Eng. Geol., 183, 1–13.
Duncan, J. M. (2000). “Factors of safety and reliability in geotechnical engineering.” J. Geotech. Geoenviron. Eng., 126(4), 307–316.
El-Ramly, H., Morgenstern, N. R., and Cruden, D. M. (2002). “Probabilistic slope stability analysis for practice.” Can. Geotech. J., 39(3), 665–683.
Fatahi, B. (2007). “Modelling of influence of matric suction induced by native vegetation on sub-soil improvement.” Ph.D. thesis, Univ. of Wollongong, Wollongong, Australia.
Fredlund, D., and Wong, D. (1989). “Calibration of thermal conductivity sensors for measuring soil suction.” Geotech. Test. J., 12(3), 188–194.
Fredlund, D. G., Morgenstern, N. R., and Widger, R. A. (1978). “The shear strength of unsaturated soils.” Can. Geotech. J., 15(3), 313–321.
Fredlund, D. G., and Rahardjo, H. (1993). Soil mechanics for unsaturated soils, Wiley, Hoboken, NJ.
Fredlund, D. G., and Xing, A. (1994). “Equations for the soil-water characteristic curve.” Can. Geotech. J., 31(4), 521–532.
Fredlund, D. G., Xing, A., Fredlund, M. D., and Barbour, S. L. (1996). “The relationship of the unsaturated soil shear to the soil-water characteristic curve.” Can. Geotech. J., 33(3), 440–448.
Garg, A., Coo, J. L., and Ng, C. W. W. (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.
Garg, A., Leung, A. K., and Ng, C. W. W. (2015b). “Comparisons of soil suction induced by evapotranspiration and transpiration of S. heptaphylla.” Can. Geotech. J., 52(12), 2149–2155.
Garg, A., Leung, A. K., Ng, C. W. W., and Hau, B. C. H. (2012). “Effects of plant transpiration on suction distribution in a vegetated soil slope.” Unsaturated soils: Research and applications, Springer, Berlin, 351–357.
Garg, A., and Ng, C. W. W. (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.
Greenway, D. R. (1987). “Vegetation and slope stability.” Slope stability: Geotechnical engineering and geomorphology, M. G. Anderson and K. S. Richards, eds., Wiley, Chichester, U.K.
Griffiths, D. V., and Fenton, G. A. (2004). “Probabilistic slope stability analysis by finite elements.” J. Geotech. Geoenviron. Eng., 130(5), 507–518.
Griffiths, D. V., Huang, J., and Fenton, G. A. (2011). “Probabilistic infinite slope analysis.” Comput. Geotech., 38(4), 577–584.
Hazra, B., Gadi, V., Garg, A., Ng, C. W. W., and Das, G. K. (2017). “Probabilistic analysis of suction in homogeneously vegetated slope.” Catena, 149, 394–401.
Ji, J., Kokutse, N., Genet, M., Fourcaud, T., and Zhang, Z. (2012). “Effect of spatial variation of tree root characteristics on slope stability. A case study on Black Locust (Robinia pseudoacacia) and Arborvitae (Platycladus orientalis) stands on the Loess Plateau, China.” Catena, 92, 139–154.
Jiang, S. H., Li, D. Q., Cao, Z. J., Zhou, C. B., and Phoon, K. K. (2014). “Efficient system reliability analysis of slope stability in spatially variable soils using Monte Carlo simulation.” J. Geotech. Geoenviron. Eng., 04014096.
Khan, Y. A., and Lateh, H. (2015). “Plant root reinforcement against local failure mechanism of natural slope.” Engineering geology for society and territory, Vol. 2, Springer, Cham, Switzerland, 1275–1280.
Lateh, H., Avani, N., and Bibalani, G. H. (2014). “Root tensile strength variations in inter and intra species in rainforest.” Int. Conf. on Chemical, Civil and Environmental Engineering (CCEE’2014), Singapore.
Leung, A. K., Garg, A., and Ng, C. W. W. (2015). “Effects of plant roots on soil-water retention and induced suction in vegetated soil.” Eng. Geol., 193, 183–197.
Li, D. Q., et al. (2015). “Bivariate distribution of shear strength parameters using copulas and its impact on geotechnical system reliability.” Comput. Geotech., 68, 184–195.
Li, D. Q., Tang, X., Zhou, C., and Phoon, K. K. (2012). “Uncertainty analysis of correlated non-normal geotechnical parameters using Gaussian copula.” Sci. China Technol. Sci., 55(11), 3081–3089.
Li, D. Q., Xiao, T., Cao, Z. J., Zhou, C. B., and Zhang, L. M. (2016). “Enhancement of random finite element method in reliability analysis and risk assessment of soil slopes using Subset Simulation.” Landslides, 13(2), 293–303.
Li, J., He, B., Chen, Y., Huang, R., Tao, J., and Tian, T. (2013). “Root distribution features of typical herb plants for slope protection and their effects on soil shear strength.” Trans. Chin. Soc. Agric. Eng., 29(10), 144–152.
Li, J. H., Zhang, L. M., and Li, X. (2011). “Soil-water characteristic curve and permeability function for unsaturated cracked soil.” Can. Geotech. J., 48(7), 1010–1031.
Li, X., Li, J. H., and Zhang, L. M. (2014). “Predicting bimodal soil-water characteristic curves and permeability functions using physically based parameters.” Comput. Geotech., 57, 85–96.
Liu, H. W., Feng, S., and Ng, C. W. W. (2016). “Analytical analysis of hydraulic effect of vegetation on shallow slope stability with different root architectures.” Comput. Geotech., 80, 115–120.
MATLAB [Computer software]. MathWorks, Natick, MA.
Nelsen, R. B. (2006). An introduction to copulas, 2nd Ed., Springer, New York.
Ng, C. W., and Pang, Y. W. (2000). “Influence of stress state on soil-water characteristics and slope stability.” J. Geotech. Geoenviron. Eng., 126(2), 157–166.
Ng, C. W. W., Woon, K. X., Leung, A. K., and Chu, L. M. (2013). “Experimental investigation of induced suction distribution in a grass covered soil.” Ecol. Eng., 52, 219–223.
Pedroso, D. M., and Williams, D. J. (2010). “A novel approach for modelling soil–water characteristic curves with hysteresis.” Comput. Geotech., 37(3), 374–380.
Phoon, K. K., ed. (2008). Reliability-based design in geotechnical engineering: Computations and applications. CRC Press, London.
Phoon, K. K., Santoso, A., and Quek, S. T. (2010). “Probabilistic analysis of soil-water characteristic curves.” J. Geotech. Geoenviron. Eng., 136(3), 445–455.
Pollen, N., Simon, A., and Collison, A. (2004). “Advances in assessing the mechanical and hydrologic effects of riparian vegetation on streambank stability.” Riparian vegetation and fluvial geomorphology, Wiley, Hoboken, NJ, 125–139.
Rees, S. W., and Ali, N. (2012). “Tree induced soil suction and slope stability.” Geomech. Geoeng., 7(2), 103–113.
Santoso, A. M., Phoon, K. K., and Quek, S. T. (2011). “Probability models for SWCC and hydraulic conductivity.” Hong Kong Polytechnic Univ., Hong Kong, China.
Sillers, W. S., and Fredlund, D. G. (2001). “Statistical assessment of soil–water characteristic curve models for geotechnical engineering.” Can. Geotech. J., 38(6), 1297–1313.
Sillers, W. S., Fredlund, D. G., and Zakerzadeh, N. (2001). “Mathematical attributes of some soil–water characteristic curve models.” Unsaturated soil concepts and their application in geotechnical practice, D. G. Toll, ed., Springer, Dordrecht, Netherlands, 243–283.
Simon, A., and Collison, A. J. (2002). “Quantifying the mechanical and hydrologic effects of riparian vegetation on streambank stability.” Earth Surf. Processes Landforms, 27(5), 527–546.
Stokes, A., et al. (2008). “How vegetation reinforces soil on slopes.” Slope stability and erosion control: Ecotechnological solutions, Springer, Dordrecht, Netherlands, 65–118.
Tang, X. S., Li, D. Q., Rong, G., Phoon, K. K., and Zhou, C. B. (2013a). “Impact of copula selection on geotechnical reliability under incomplete probability information.” Comput. Geotech., 49, 264–278.
Tang, X. S., Li, D. Q., Zhou, C. B., Phoon, K. K., and Zhang, L. M. (2013b). “Impact of copulas for modelling bivariate distributions on system reliability.” Struct. Saf., 44, 80–90.
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.
Wu, X. Z. (2013a). “Probabilistic slope stability analysis by a copula-based sampling method.” Computa. Geosci., 17(5), 739–755.
Wu, X. Z. (2013b). “Trivariate analysis of soil ranking-correlated characteristics and its application to probabilistic stability assessments in geotechnical engineering problems.” Soils Found., 53(4), 540–556.
Wu, X. Z. (2015). “Modelling dependence structures of soil shear strength data with bivariate copulas and applications to geotechnical reliability analysis.” Soils Found., 55(5), 1243–1258.
Yang, L., Wei, W., Chen, L., Chen, W., and Wang, J. (2014). “Response of temporal variation of soil moisture to vegetation restoration in semi-arid Loess Plateau, China.” Catena, 115, 123–133.
Zhai, Q., and Rahardjo, H. (2012). “Determination of soil–water characteristic curve variables.” Comput. Geotech., 42, 37–43.
Zhai, Q., and Rahardjo, H. (2013). “Quantification of uncertainties in soil-water characteristic curve associated with fitting parameters.” Eng. Geol., 163, 144–152.
Zhang, J. (2013). “Shallow slope stability analysis method for vegetated slope.” 2nd Int. Conf. on Geotechnical and Earthquake Engineering, ASCE, Reston, VA, 388–395.
Zhang, L., Zeng, J., and Cheng, Y. (2014). “Model uncertainty of unsaturated hydraulic properties and effects on slope reliability.” Vulnerability, uncertainty, and risk: Quantification, mitigation, and management, ASCE, Reston, VA.
Zhu, H., and Zhang, L. M. (2015). “Evaluating suction profile in a vegetated slope considering uncertainty in transpiration.” Comput. Geotech., 63, 112–120.
Zhu, H., and Zhang, L. M. (2016). “Field investigation of erosion resistance of common grass species for soil bioengineering in Hong Kong.” Acta Geotechnica, 11(5), 1047–1059.
Zhu, H., Zhang, L. M., Xiao, T., and Li, X. Y. (2017). “Enhancement of slope stability by vegetation considering uncertainties in root distribution.” Comput. Geotech., 85, 84–89.
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ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part A: Civil Engineering
Volume 3 • Issue 4 • December 2017
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©2017 American Society of Civil Engineers.
History
Received: Dec 6, 2016
Accepted: May 31, 2017
Published online: Oct 12, 2017
Published in print: Dec 1, 2017
Discussion open until: Mar 12, 2018
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