Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Influence of Estimation of Hydraulic Conductivity Function on Rainfall Infiltration into Unsaturated Soil Slope

투수계수함수의 추정이 불포화 토사 사면의 강우 침투거동에 미치는 영향

  • Cho, Sung-Eun (Dept. of Civil, Safety, and Environmental Engrg. & Construction Engrg. Research Institute, Hankyong National Univ.)
  • 조성은 (한경대학교 토목안전환경공학과)
  • Received : 2017.06.05
  • Accepted : 2017.09.12
  • Published : 2017.09.30
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Abstract

The procedure that combines the result of infiltration analysis into stability analysis based on the limit equilibrium method is widely used to evaluate the impact of rainfall infiltration on slope stability. Accurate prediction of rainfall infiltration is essential to the prediction of landslides caused by rainfall, requires to obtain accurate unsaturated hydraulic properties of the soil. Among the unsaturated hydraulic characteristics of the soil, the importance of the soil-water characteristic curve describing the retained water characteristics of the soil is relatively well known and the measurement by test method to obtain the SWCC is gradually increasing. However, it takes a lot of time and expenses to experimentally measure the unsaturated conductivity characteristics of the soil. Therefore, it is common practice to estimate the hydraulic conductivity function from the SWCC. Although it is widely known that the SWCC has a great influence on rainfall infiltration, studies on the effect of the hydraulic conductivity function estimated from the SWCC on rainfall infiltration are very limited. In this study, we explained how the estimation model of the hydraulic conductivity function affects rainfall infiltration and slope stability analysis. To this end, one-dimensional infiltration analysis and slope stability analysis were conducted by using the data on the SWCC of weathered granite soil widely distributed in Korea. The applicability of each estimation model is discussed through review of the analysis results.

강우가 사면안정에 미치는 영향을 고려하기 위해 강우의 침투해석을 수행한 후 그 결과를 사면안정해석에 적용하는 안정해석 절차가 널리 사용되고 있다. 강우에 의한 산사태를 예측하기 위해서는 강우의 침투거동을 정확하게 예측하는 것이 필수적이며 이를 위해서는 지반의 불포화 수리특성을 정확하게 파악하는 것이 매우 중요하다. 지반의 불포화 수리특성 중 지반의 보유 수분특성을 나타내는 함수특성곡선에 대해서는 그 중요성이 비교적 널리 알려져 있으며 이를 파악하기 위한 시험방법의 적용도 점차 증가하고 있다. 그러나 지반의 불포화 투수특성을 실험적으로 파악하는 것은 시간과 비용이 많이 소요되므로 지반의 함수특성곡선으로부터 추정하는 방법이 널리 활용되고 있다. 지반의 함수특성이 강우의 침투에 큰 영향을 미치는 것은 널리 알려져 있지만, 함수특성곡선으로부터 추정된 불포화 투수특성이 강우의 침투에 미치는 영향에 대한 연구는 매우 제한적인 형편이다. 본 연구에서는 우리나라에 분포하는 화강풍화토에 대한 함수특성곡선 자료를 바탕으로 투수계수함수를 추정하는 모델이 사면을 통한 강우의 침투 및 사면안정 해석에 어떻게 영향을 미치는지 설명하기 위하여 일차원 침투해석 및 무한사면 해석을 수행하였다. 해석 결과의 분석을 통하여 각 추정모델의 적용성에 대하여 논하였다.

Keywords

References

  1. Baum, R. L., Godt, J. W., and Savage, W. Z. (2010), "Estimating the Timing and Location of Shallow Rainfall-induced Landslides using a Model for Transient, Unsaturated Infiltration", Journal of Geophysical Research, Vol.115, doi:10.1029/2009JF001321.
  2. Burdine, N. T. (1953), "Relative Permeability Calculations from Pore-size Distribution Data", Petroleum Transactions Am Inst Min Eng, Vol.198, pp.71-77.
  3. Cho, S. E. (2009), "Infiltration Analysis to Evaluate the Surficial Stability of Two-layered Slopes Considering Rainfall Characteristics", Engineering Geology, Vol.105, No.1-2, pp.32-43. https://doi.org/10.1016/j.enggeo.2008.12.007
  4. Cho, S.E. (2014), "Probabilistic Stability Analysis of Rainfall-induced Landslides Considering Spatial Variability of Permeability", Engineering Geology, Vol.171, pp.11-20. https://doi.org/10.1016/j.enggeo.2013.12.015
  5. Cui, J. L. (2007), Prediction of permeability for unsaturated weathered granite soils based on soil-water characteristic curve, Master thesis, KAIST.
  6. Dye, H. B., Houston, S. L., and Welfertand, B. D. (2011), "Influence of Unsaturated Soil Properties Uncertainty on Moisture Flow Modeling", Geotechnical and Geological Engineering, Vol.29, No.2, pp.161-169. https://doi.org/10.1007/s10706-009-9281-0
  7. Fredlund, D. G. and Xing, A. (1994), "Equations for the Soil-water Characteristic Curve", Canadian Geo-technical Journal, Vol.31, No.4, pp.521-532. https://doi.org/10.1139/t94-061
  8. Fredlund, D. G., Xing, A., and Huang, S. (1994), "Predicting the Permeability Function for Unsaturated Soils using the Soil-water Characteristic Curve", Canadian Geotechnical Journal, Vol.31, pp.533-546. https://doi.org/10.1139/t94-062
  9. Gardner, W. R. (1958), "Some Steady-state Solutions of the Unsaturated Moisture Flow Equation with Application to Evaporation from a Water Table", Soil Science, Vol.85, pp.228-232. https://doi.org/10.1097/00010694-195804000-00006
  10. Geo-Slope (2012), Seepage modeling with seep/w 2012 Version, GEO-SLOPE International Ltd, Calgary, Alberta, Canada.
  11. Kim, J. H., Lee, K. W., Jeong S. S., and Kim, K. S. (2014), "GIS-based Prediction Method of Landslide Susceptibility using a Rainfall Infiltration-groundwater Flow Model", Engineering Geology, Vol.182, pp.63-78. https://doi.org/10.1016/j.enggeo.2014.09.001
  12. Kim, Y. K. (2003), Permeability of unsaturated weathered soils by analyzing triaxial permeameter test results, Master thesis, KAIST.
  13. Lee, S. R., Oh, T. K., Kim, Y. K., and Kim, H. C. (2009), "Influence of Rainfall Intensity and Saturated Permeability on Slope Stability during Rainfall Infiltration", Journal of Korean Geotechnical Society, Vol.25, No.1, pp.65-76.
  14. Leji, F. L., Russel, W. B., and Lesch, S. M. (1996), "Closed-form Expressions for Water Retention and Conductivity Data", Ground Water, Vol.35, No.5, pp.848-858. https://doi.org/10.1111/j.1745-6584.1997.tb00153.x
  15. Lu, N. and Godt, J. (2013), Hillslope Hydrology and Stability, Cambridge University Press, New York.
  16. 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
  17. Ng, C. W. W. and Pang, Y. W. (2000), "Influence of Stress State on Soil-water Characteristics and Slope Stability", Journal of Geotechnical and Geoenvironmental Engineering, Vol.126., No.2, pp. 157-166. https://doi.org/10.1061/(ASCE)1090-0241(2000)126:2(157)
  18. 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
  19. Oh, S. B., Kim, Y. K., and Kim, J. W. (2015), "A Modified van Genuchten-Mualem Model of Hydraulic Conductivity in Korean Residual Soils", Water, Vol.7, No.10, pp.5487-5502. https://doi.org/10.3390/w7105487
  20. Oh, S. B., Park, K. H., and Kim, J. W. (2014), "A Hydraulic Conductivity Model Considering the Infiltration Characteristics Near Saturation in Unsaturated Slopes", Journal of Korean Geotechnical Society, Vol.30, No.1, pp.37-47. https://doi.org/10.7843/KGS.2014.30.1.37
  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. Santoso, A. M., Phoon, K. K., and Quek, S. T. (2011), "Effects of Soil Spatial Variability on Rainfall-induced Landslides", Computers and Structures, Vol.89, No.11-12, pp.893-900. https://doi.org/10.1016/j.compstruc.2011.02.016
  23. Savage, W. Z., Godt, J. W., and Baum, R. L. (2004), Modeling time-dependent slope stability. In: Proceedings of the 9th International Symposium on Landslides, Rio de Janeiro, Brazil, pp.23-38.
  24. Schaap, M. G. and van Genuchten, M. T. (2006), "A Modified Mualem-van Genuchten Formulation for Improved Description of the Hydraulic Conductivity Near Saturation", Vadose Zone J., Vol. 5, No.1, pp.27-34. https://doi.org/10.2136/vzj2005.0005
  25. Srivastava, R. and Yeh, T. C. J. (1991), "Analytical Solutions for one Dimension Transient Infiltration Toward the Water Table in Homogeneous and Layered Soils", Water Resources Research, Vol.27, No.5, pp.753-762. https://doi.org/10.1029/90WR02772
  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. Vogel, T., van Genuchten, M. T., and Cislerova, M. (2001), "Effect of the shape of the soil hydraulic functions near saturation on variably saturated flow predictions", Advances in Water Resources, Vol.24, No.2, pp.133-144. https://doi.org/10.1016/S0309-1708(00)00037-3