Estimating Slope Stability Reduction due to Rain Infiltration Mounding
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 132, Issue 9
Abstract
Rainwater can infiltrate into slopes and earth dams. Given sufficient infiltrating rainfall intensity, frequency, and time, the phreatic line within the slope or dam will “mound” above its otherwise steady state position. Such a mound will increase downslope seepage and reduce downslope stability. This paper develops an approximate method for solving this transient seepage “mounding problem” and the resulting reduction in stability. It shows the following variables will reduce stability: increased rainfall intensity and duration, decreasing permeability—especially over the range—and its anisotropy, increasing the slope cotangent, decreasing the depth to an impermeable underlayer, or increasing the depth to a permeable underlayer. Increasing size and effective porosity has only a time effect. In special circumstances the mounding effect can reduce slope stability by 50% and the paper includes a slope case history example.
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Acknowledgments
T. William Lambe and Francisco Silva-Tulla reviewed some of the writer’s initial work on the “mounding problem” in conjunction with our common investigation of a tailings dam failure in Florida. They encouraged the effort to produce a Technical Note, which then grew into this paper. The writer also thanks Loadtest, Inc., Gainesville, Fla., for its support in preparing this paper, and Suzanne Terrell and John Graman particularly for word processing and graphics, respectively.
References
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Morgenstern, N. (1963). “Stability charts for earth slopes during rapid drawdown.” Geotechnique, 13(2), 121–131.
Newlin, C. W., and Rossier, S. C. (1967). “Embankment drainage after instantaneous drawdown.” J. Soil Mech. Found. Div., 93(6), 79–95.
Schmertmann, J. H. (2004). “Discussion of ‘Time for development of internal erosion and piping in embankment dams’ by Fell, R., et al.” J. Geotech. Geoenviron. Eng., 130, 980–980.
Zhang, J., Jiao, J. J., and Yang, J. (2000). “In situ rainfall infiltration studies at a hillside in Hubei Province, China.” Eng. Geol. (Amsterdam), 57, 31–38.
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Information
Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 132 • Issue 9 • September 2006
Pages: 1219 - 1228
Copyright
© 2006 ASCE.
History
Received: Jun 3, 2005
Accepted: Feb 6, 2006
Published online: Sep 1, 2006
Published in print: Sep 2006
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