Effective Stress-Based Limit-Equilibrium Analysis for Homogeneous Unsaturated Slopes
Publication: International Journal of Geomechanics
Volume 16, Issue 6
Abstract
With a suction stress–based effective stress representation, stability analysis of unsaturated engineered and natural slopes can be performed effectively in the same manner as the classical limit-equilibrium (LE) methodologies. This paper presents an analytical framework for effective stress LE analysis of unsaturated homogeneous slopes under steady one-directional (vertical) flow. The proposed log spiral failure surface–based LE method involves only two additional hydromechanical parameters for unsaturated soil, approximating the inverse of the air-entry pressure and pore-size distribution. Both parameters are used to describe seepage and effective stress variations in unsaturated soils. Unlike most other LE formulations, the method is statically determinate. A parametric study was performed, and stability charts for general use are presented. The impact of infiltration and evaporation on the stability of slopes for four hypothetical soil types was studied. It is shown that the apparent cohesion due to suction stress may contribute substantially to the stability of slopes. Specifically, different seepage rates can significantly impact the stability of clayey slopes. This impact progressively decreases in silty slopes and further diminishes in loess and sand. Because the proposed method is statically free of assumptions, it can serve as a benchmark for rigorous slope stability methods that can deal with more complex problems.
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References
Baker, R. (1981). “Tensile strength, tension cracks, and stability of slopes.” Soils Found., 21(2), 1–17.
Bathurst, R. J., Walters, D. L., Hatami, K., and Allen, T. M. (2001). “Full-scale performance testing and numerical modelling of reinforced soil retaining walls”. Proc., 4th Int. Symp. on Earth Reinforcement, H. Ochiai, J. Otani, N. Yasufuku, and K. Omine, eds., Vol. 2, Balkema, Rotterdam, Netherlands, 777–799.
Bishop, A. W. (1955). “The use of slip circles in the stability analysis of earth slopes.” Géotechnique, 5(1), 7–17.
Bishop, A. W. (1959). “The principle of effective stress.” Tek. Ukeblad, 106(39), 859–863.
Cai, F., and Ugai, K. (2004). “Numerical analysis of rainfall effects on slope stability.” Int. J. Geomech., 69–78.
Cho, S. E., and Lee, S. R. (2002). “Evaluation of surficial stability for homogeneous slopes considering rainfall characteristics.” J. Geotech. Geoenviron. Eng., 756–763.
Damiano, E., and Mercogliano, P. (2013). “Potential effects of climate change on slope stability in unsaturated pyroclastic soils.” Landslide science and practice: Global environmental change, C. Margottini, P. Canuti, and K. Sassa eds., Vol. 4, Taylor & Francis Group, London, 15–25.
Damiano, E., Olivares, L., and Picarelli, L. (2012). “Steep-slope monitoring in unsaturated pyroclastic soils.” Eng. Geol., 137–138(6), 1–12.
Duncan, J. M., and Wright, S. G. (2005). Soil strength and slope stability, John Wiley & Sons, Hoboken, NJ.
Fourie, A. B., Rowe, D., and Blight, G. E. (1999). “The effect of infiltration on the stability of the slopes of a dry ash dump.” Géotechnique, 49(1), 1–13.
Fredlund, D. G., and Morgenstern, N. R. (1977). “Stress state variables for unsaturated soils.” J. Geotech. Eng. Div., 103(5), 447–466.
Fredlund, D. G., and Rahardjo, H. (1993). Soil mechanics for unsaturated soils, John Wiley & Sons, Inc., New York.
Gardner, W. R. (1958). “Some steady state solutions of the unsaturated moisture flow equation with application to evaporation from a water table.” Soil Sci., 85(4), 228–232.
Gavin, K., and Xue, J. (2010). “Design charts for the stability analysis of unsaturated soil slopes.” Geotech. Geol. Eng., 28(1), 79–90.
Godt, J. W., Baum, R. L., and Lu, N. (2009). “Landsliding in partially saturated materials.” Geophys. Res. Lett., 36(2), L02403
Griffiths, D. V., and Lu, N. (2005). “Unsaturated slope stability analysis with steady infiltration or evaporation using elasto-plastic finite elements.” Int. J. Numer. Anal. Meth. Geomech., 29(3), 249–267.
Janbu, N. (1954). “Stability analysis of slopes with dimensionless parameters,” Harvard Soil Mechanics Series 46, Harvard University Press, Cambridge, MA.
Khalilnejad, A., Ali, F., Hashim, R., and Osman, N. (2013). “Finite-element simulation for contribution of matric suction and friction angle to stress distribution during pulling-out process.” Int. J. Geomech., 527–532.
Hamdhan, I. N., and Schweiger, H. F. (2013). “Finite element method–based analysis of an unsaturated soil slope subjected to rainfall infiltration.” Int. J. Geomech., 653–658.
Leshchinsky, D. (1997) “Design procedure for geosynthetic reinforced steep slopes.” Technical Rep. REMR-GT-23, Geotechnical Laboratory, U.S. Army Corps of Engineers, Waterways Experiment Station, Vicksburg, MS.
Leshchinsky, D., Ling, H. I., Wang, J.-P., Rosen, A., and Mohri, Y. (2009). “Equivalent seismic coefficient in geocell retention systems.” Geotext. Geomembr., 27(1), 9–18.
Leshchinsky, D., and Mullett, T. L. (1988). “Design charts for vertical cuts.” J. Geotech. Eng., 337–344.
Leshchinsky, D., and San, K.-C. (1994). “Pseudostatic seismic stability of slopes: Design charts.” J. Geotech. Eng., 1514–1532.
Leshchinsky, D., and Zhu, F. (2010). “Resultant force of lateral earth pressure in unstable slopes.” J. Geotech. Geoenviron. Eng., 1655–1663.
Likos, W. J., Lu, N., and Godt, J. W. (2014). “Hysteresis and uncertainty in soil water-retention curve parameters.” J. Geotech. Geoenviron. Eng., 04013050.
Lu, N. (2008). “Is matric suction a stress variable?” J. Geotech. Geoenviron. Eng., 899–905.
Lu, N., and Godt, J. (2008). “Infinite slope stability under steady unsaturated seepage conditions.” Water Resour. Res., 44(11), W11404.
Lu, N., Godt, J. W., and Wu, D. T. (2010). “A closed-form equation for effective stress in unsaturated soil.” Water Resour. Res., 46(5), W05515.
Lu, N., Kaya, M., Collins, B. D., and Godt, J. W. (2013a). “Hysteresis of unsaturated hydromechanical properties of a silty soil.” J. Geotech. Geoenviron. Eng., 507–510.
Lu, N., and Likos, W. J. (2004). Unsaturated soil mechanics, John Wiley & Sons, New York.
Lu, N., and Likos, W. J. (2006). “Suction stress characteristic curve for unsaturated soil.” J. Geotech. Geoenviron. Eng., 131–142.
Lu, N., Wayllace, A., and Oh, S. (2013b). “Infiltration-induced seasonally reactivated instability of a highway embankment near the Eisenhower Tunnel, Colorado, USA.” Eng. Geol., 162, 22–32.
Morgenstern, N. R., and Price, V. E. (1965). “The analysis of the stability of general slip surfaces.” Géotechnique, 15(1), 79–93.
Mualem, Y. (1976). “A new model for predicting hydraulic conductivity of unsaturated porous media.” Water Resour. Res., 12(3), 513–522.
Ng, C. W. W., and Shi, Q. (1998). “A numerical investigation of the stability of unsaturated soil slopes subjected to transient seepage.” Comput. Geotech., 22(1), 1–28.
Rahardjo, H., Rezaur, R. B., Leong, E. C., Alonso, E. E., Lloret, A., and Gens, A. (2008). “Monitoring and modeling of slope response to climatic changes.” Proc., 10th Int. Symp. on Landslides and Engineered Slopes, Z. Chen, J.-M. Zhang, K. Ho, F.-Q. Wu, and Z.-K. Li, eds., CRC, London, 67–84.
Rahardjo, H., Satyanaga, A., and Leong, E. C. (2012). “Unsaturated soil mechanics for slope stabilization.” Geotech. Eng. J. SEAGS AGSSEA, 43(1), 48–58.
Sivakumar Babu, G. L., and Murthy, D. S. (2005). “Reliability analysis of unsaturated soil slopes.” J. Geotech. Geoenviron. Eng., 1423–1428.
Sorbino, G., and Nicotera, M. V. (2013). “Unsaturated soil mechanics in rainfall-induced flow landslides.” Eng. Geol., 165(10), 105–132.
Spencer, E. (1967). “A method of analysis of the stability of embankments assuming parallel inter-slice forces.” Géotechnique, 17(1), 11–26.
Springman, S. M., Jommi, C., and Teysseire, P. (2003). “Instabilities on moraine slopes induced by loss of suction: A case history.” Géotechnique, 53(1), 3–10.
Taylor, D. W. (1937). “Stability of earth slopes.” J. Boston Soc. Civ. Eng., 24(3), 197–246.
Travis, Q. B., Houston, S. L., Marinho, F. A. M., and Schmeeckle, M. (2010). “Unsaturated infinite slope stability considering surface flux conditions.” J. Geotech. Geoenviron. Eng., 963–974.
USGCRP (U.S. Global Change Research Program). (2009). Global climate change impacts in the United States, Cambridge University Press, Cambridge, U.K.
Utili, S. (2013). “Investigation by limit analysis on the stability of slopes with cracks.” Géotechnique, 63(2), 140–154.
Vahedifard, F., Leshchinsky, B. A., Mortezaei, K., and Lu, N. (2015). “Active earth pressures for unsaturated retaining structures.” J. Geotech. Geoenviron. Eng., 04015048.
Vahedifard, F., Leshchinsky, B. A., Sehat, S., and Leshchinsky, D. (2014). “Impact of cohesion on seismic design of geosynthetic-reinforced earth structures.” J. Geotech. Geoenviron. Eng., 04014016.
Vahedifard, F., Leshchinsky, D., and Meehan, C. L. (2012). “Relationship between the seismic coefficient and the unfactored geosynthetic force in reinforced earth structures.” J. Geotech. Geoenviron. Eng., 1209–1221.
Vahedifard, F., Leshchinsky, D., and Meehan, C. L. (2013). “Displacement-based internal design of geosynthetic-reinforced earth structures subjected to seismic loading conditions.” Géotechnique, 63(6), 451–462.
van Genuchten, M. T. (1980). “A closed-form equation predicting the hydraulic conductivity of unsaturated soils.” Soil Sci. Soc. Am. J., 44(5), 892–898.
Vanapalli, S. K., Fredlund, D. E., Pufahl, D. E., and Clifton, A. W. (1996). “Model for the prediction of shear strength with respect to soil suction.” Can. Geotech. J., 33(3), 379–392.
Yeh, T.-C. (1989). “One-dimensional steady-state infiltration in heterogeneous soils.” Water Resour. Res., 25(10), 2149–2158.
Zornberg, J. G., Sitar, N., and Mitchell, J. K. (1998). “Performance of geosynthetic reinforced slopes at failure.” J. Geotech. Geoenviron. Eng., 670–683.
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© 2016 American Society of Civil Engineers.
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Received: Oct 2, 2014
Accepted: Jun 10, 2015
Published online: Jan 28, 2016
Discussion open until: Jun 28, 2016
Published in print: Dec 1, 2016
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