DOI QR코드

DOI QR Code

Stability Analysis of Unsaturated Soil Slope by Coupled Hydro-mechanical Model Considering Air Flow

공기흐름을 고려한 수리-역학적 연동모델에 의한 불포화 토사사면의 안정해석

Cho, Sung-Eun
조성은

  • Received : 2015.09.29
  • Accepted : 2016.01.12
  • Published : 2016.01.31

Abstract

Stability analysis based on the limit equilibrium method combined with the result of infiltration analysis is commonly used to evaluate the effect of rainfall infiltration on the slope stability. Soil is a three-phase mixture composed of solid particle, water and air. Therefore, a fully coupled mixture theories of stress-deformation behavior and the flow of water and air should be used to accurately analyze the process of rainfall infiltration through soil slope. The purpose of this study is to study the effect of interaction of air and water flow on the mechanical stability of slope. In this study, stability analyses based on the coupled hydro-mechanical model of three-phases were conducted for slope of weathered granite soil widespread in Korea. During the process of hydro-mechanical analysis strength reduction technique was applied to evaluate the effect of rainfall infiltration on the slope stability. The results showed an increase of air pressure during infiltration because rain water continuously displaced the air in the unsaturated zone. Such water-air interaction in the pore space of soil affects the stress-deformation behavior of slope. Therefore, the results from the three-phase model showed different behavior from the solid-water model that ignores the transport effect of air in the pores.

Keywords

Slope stability;Coupled hydro-mechanical analysis;Rainfall infiltration;Strength reduction method;Air flow

References

  1. Alonso, E., Gens, A., and Lloret, A. (1995), "Effect of Rain Infiltration on the Stability of Slopes", Proceedings of the First Int. Conf. on Unsaturated Soils, Paris, pp.241-249.
  2. Bishop, A. W. (1959), "The Principle of Effective Stress", Teknisk Ukeblad, Vol.106, No.39, pp.859-863.
  3. Borja, R. I. and White, J. A. (2010), "Continuum Deformation and Stability Analyses of a Steep Hillside Slope under Rainfall Infiltration", Acta Geotechnica, Vol.5, pp.1-14, doi:10.1007/s11440-009-01080-1. https://doi.org/10.1007/s11440-009-0108-1
  4. Borja, R. I., White, J. A., Liu, X., and Wu, W. (2012), "Factor of Safety in a Partially Saturated Slope Inferred from Hydromechanical Continuum Modeling", International Journal for Numerical and Analytical Methods in Geomechanics, Vol.36, No.2, pp.236-248. https://doi.org/10.1002/nag.1021
  5. Cheng, Y. M., Lansivaara, L., and Wei, W. B. (2007), "Twodimensional Slope Stability Analysis by Limit Equilibrium and Strength Reduction Methods", Computers Geotechnics, Vol.34, No.3, pp.137-150. https://doi.org/10.1016/j.compgeo.2006.10.011
  6. Chapuis, R. P. and Aubertin, M. (2003), "On the use of the Kozeny- Carman Equation to Predict the Hydraulic Conductivity of Soils", Canadian Geotechnical Journal, Vol.40, No.3, pp.616-628. https://doi.org/10.1139/t03-013
  7. Cho, S. E. (2014), "Study on the Characteristics of Infinite Slope Failures by Probabilistic Seepage Analysis", Journal of Korean Geotechnical Society, Vol.30, No.10, pp.5-18.
  8. Cho, S. E. and Lee, S. R. (2001), "Instability of Unsaturated Soil Slopes due to Infiltration", Computers and Geotechnics, Vol.28, No.3, pp.185-208. https://doi.org/10.1016/S0266-352X(00)00027-6
  9. Fredlund, D. G. and Rahardjo, H. (1995), Soil mechanics for unsaturated soils. New York: John Wiley & Sons.
  10. Fredlund, D. G., Rahardjo, H., and Fredlund, M. D. (2012), Unsaturated Soil Mechanics in Engineering Practice, John Wiley & Sons, New York.
  11. Hu, R., Chen, Y. F., and Zhou, C. B. (2011), "Modeling of Coupled Deformation, Water Flow and Gas Transport in Soil Slopes Subjected to Rain Infiltration", Science China Technological Sciences, Vol.54, No.10, pp.2561-2575. https://doi.org/10.1007/s11431-011-4504-z
  12. Itasca (2011), User's Manual : Fluid-Mechanical Interaction, FLAC 7.0, Itasca Consulting Group Inc. Minneapolis.
  13. Kim, J. H. and Hwang, Y. C. (2011), "Finite Element Analysis of Partially Saturated Soil Considering Pore-air Pressure", Journal of Korean Geotechnical Society, Vol.27, No.3, pp.95-102. https://doi.org/10.7843/kgs.2011.27.3.095
  14. Kim, J. H., Im, J. S., and Park, S. W. (2012), "Hydro-mechanical behavior of Partially Saturated Soil Slopes under Rainfall", Journal of Korean Geotechnical Society, Vol.28, No.11, pp.69-78.
  15. Kim, J. H., Im, J. S., and Park, S. W. (2014), "Coupled Finite Element Analysis of Partially Saturated Soil Slope Stability", Journal of Korean Geotechnical Society, Vol.30, No.4, pp.35-45. https://doi.org/10.7843/kgs.2014.30.4.35
  16. Kim, Y. K. (2003), Permeability of unsaturated weathered soils by analyzing triaxial permeameter test results, Master thesis, KAIST.
  17. Kim, Y. S., Kim, J. H., Kim, T. H., and Lee, J. K. (2014), "Comparison between Soil Drainage Experiment and Finite Element Analysis for Air Diffusion in Multiphase Porous Media", Journal of Korean Geotechnical Society, Vol.30, No.2, pp.77-85. https://doi.org/10.7843/kgs.2014.30.2.77
  18. Lu, N. and Godt, J. (2013), Hillslope Hydrology and Stability, Cambridge University Press, New York.
  19. Mualem, Y. (1976), "A New Model for Predicting the Hydraulic Conductivity of Unsaturated Porous Media", Water Resources Research, Vol.12, No.3, pp.513-522. https://doi.org/10.1029/WR012i003p00513
  20. Ng, C. W. W. and Shi, Q. (1998), "A Numerical Investigation of the Stability of Unsaturated Soil Slopes Subjected to Transient Seepage", Computers and Geotechnics, Vol.22, No.1, pp.1-28. https://doi.org/10.1016/S0266-352X(97)00036-0
  21. Richards, L. A. (1931), "Capillary Conduction of Liquids through Porous Mediums", Physics, Vol.1, No.5, pp.318-333. https://doi.org/10.1063/1.1745010
  22. Shin, H. S. (2011), "Formulation of Fully Coupled THM behavior in Unsaturated Soil", Journal of Korean Geotechnical Society, Vol.27, No.3, pp.75-83.
  23. Sun, D. M., Zang, Y. G., and Semprich, S. (2015), "Effects of Airflow Induced by Rainfall Infiltration on Unsaturated Soil Slope Stability", Transport in Porous Media, Vol.107, No.3, pp.821-841. https://doi.org/10.1007/s11242-015-0469-x
  24. Touma, J. and Vauclin, M. (1986), "Experimental and Numerical Analysis of Two Phase Infiltration in a Partially Saturated Soil", Transport in Porous Media, Vol.1, No.1, pp.27-55. https://doi.org/10.1007/BF01036524
  25. Ugai, K. and Leshchinsky, D. (1995), "Three-dimensional Limit Equilibrium and Finite Element Analysis: A Comparison of Results", Soils and Foundation, Vol.35, No.4, pp.1-7.
  26. van Genuchten, M. T. (1980), "A Closed-form Equation for Predicting the Hydraulic Conductivity of Unsaturated Soils", Soil Science Society America Journal, Vol.44, No.5, pp.892-898. https://doi.org/10.2136/sssaj1980.03615995004400050002x
  27. Zhang, L. L., Fredlund, D. G., Zhang, L. M., and Tang, W. H. (2004), "Numerical Study of Soil Conditions under which Matric Suction Can be Maintained", Canadian Geotechnical Journal, Vol.41, No.4, pp.569-582. https://doi.org/10.1139/t04-006
  28. Zhang, X. Y., Zhu, Y. M., and Fang, C. H. (2009), "The Role for Air Flow in Soil Slope Stability Analysis", Journal of Hydrodynamics, Vol.21, No.5, pp.640-646. https://doi.org/10.1016/S1001-6058(08)60195-X
  29. Zienkiewicz, O. C., Humpheson, C., and Lewis, R. W. (1975), "Associated and Nonassociated Visco-plasticity and Plasticity in Soil Mechanics", Geotechnique, Vol.25, No.4, pp.671-689. https://doi.org/10.1680/geot.1975.25.4.671

Acknowledgement

Supported by : 한국연구재단, 국토교통과학기술진흥원