Unsaturated 3D Column Method: New Method for Evaluation of Stability of Unsaturated Slopes Subjected to Vertical Steady-State Infiltration and Evaporation
Publication: International Journal of Geomechanics
Volume 21, Issue 10
Abstract
A new analytical method for investigating the stability of unsaturated soil slopes was developed by considering a 3D failure wedge under different steady-state infiltration and evaporation. In this light, the general limit equilibrium approach and concept of effective stress in unsaturated soils were implemented. An extensive parametric study was performed as well, to study the effect of slope geometry, unsaturated soil properties and/or state/material variables, position of groundwater level (GWL), and infiltration and evaporation flow rates on the stability of soil slopes against failure and landslide. In addition, a quantitative comparison was made between the safety factors obtained from the proposed unsaturated 3D analysis and those obtained from two-dimensional (2D) and three-dimensional (3D) classical slope stability analysis. It was revealed that the steady-state infiltration/evaporation has a significant influence on the stability of the silty and clayey soil slopes. In addition, the geometrical aspects of the slope and the hydromechanical parameters of the soil largely affect the safety factor of soil slopes against failure. Results show that the safety factors obtained from unsaturated 3D analyses for the silty and clayey slopes are remarkably different from those obtained from 2D and 3D classical calculations; however, negligible differences were found for the sandy slopes in that respect. In addition, a comparative study was performed on the impact of governing parameters on the safety factors of unsaturated slopes under infiltration and evaporation using an unsaturated 3D column method. It was revealed that infiltration has a pronounced effect on the safety factor compared with that for evaporation and that silty and clayey slopes are more affected by evaporation and infiltration than sandy slopes. In general, this study showed that applying unsaturated soil mechanics concepts to 3D stability analysis not only leads to more precise safety factors against the slope failure and landslide initiation but may also reduce the uncertain conservatism considerations in some practical problems.
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Acknowledgments
This research has been financially supported by Sharif University of Technology, which is greatly acknowledged. In addition, the second author would like to thank the Niroo Research Institute for providing him with the opportunity to contribute to this research. In addition, the authors would like to acknowledge Mr. Mohammad Javad Mashinchian for his partial contribution in developing the analytical formulations.
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International Journal of Geomechanics
Volume 21 • Issue 10 • October 2021
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© 2021 American Society of Civil Engineers.
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Received: Sep 21, 2020
Accepted: May 1, 2021
Published online: Jul 23, 2021
Published in print: Oct 1, 2021
Discussion open until: Dec 23, 2021
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