Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
권호 표지
DOI QR코드

DOI QR Code

Probabilistic Stability Analysis of Unsaturated Soil Slope under Rainfall Infiltration

강우침투에 대한 불포화 토사사면의 확률론적 안정해석

  • Cho, Sung-Eun (Dept. of Civil, Safety, and Environmental Engrg. & Construction Engrg. Research Institute, Hankyong National Univ.)
  • 조성은 (한경대학교 토목안전환경공학과)
  • Received : 2018.01.31
  • Accepted : 2018.04.17
  • Published : 2018.05.31
Download PDF
⟨ Previous Next ⟩

Abstract

The slope failure due to the rainfall infiltration occurs frequently in Korea, since the depth of the weathered residual soil layer is shallow in mountainous region. Depth of the failure surface is shallow and tends to pass near the interface between impermeable bedrock and soil layer. Soil parameters that have a significant impact on the instability of unsaturated slopes due to rainfall infiltration inevitably include large uncertainties. Therefore, this study proposes a probabilistic analysis procedure by Monte Carlo Simulation which considers the hydraulic characteristics and strength characteristics of soil as random variables in order to predict slope failure due to rainfall infiltration. The Green-Ampt infiltration model was modified to reflect the boundary conditions on the slope surface according to the rainfall intensity and the boundary condition of the shallow impermeable bedrock was introduced to predict the stability of unsaturated soil slope with shallow bedrock under constant rainfall intensity. The results of infiltration analysis were used as inputs of infinite slope analysis to calculate the safety factor. The proposed analysis method can be used to calculate the time-dependent failure probability of soil slope due to rainfall infiltration.

우리나라의 산지사면은 풍화잔류토 층의 깊이가 얕아 강우의 침투로 인한 사면파괴가 많이 발생한다. 이때 파괴면의 깊이는 얕고 토사층과 기반암의 경계면 근처를 통과하는 특징을 가지고 있다. 강우의 침투로 인한 불포화 토사사면의 불안정성에 중요한 영향을 미치는 지반 정수들은 큰 불확실성을 포함한다. 따라서 본 연구에서는 강우로 인한 사면파괴를 예측하기 위하여 지반의 수리학적 특성과 강도특성을 랜덤변수로 고려하는 몬테카를로 시뮬레이션에 의한 확률론적 해석 절차를 제안하였다. 일정한 강우강도에 대한 기반암이 얕게 존재하는 불포화 토사사면의 안정성 예측을 위하여 강우강도에 따른 사면 표면에서의 경계조건을 반영하여 Green-Ampt 모델을 수정하고 얕은 기반암의 경계조건을 도입하였다. 침투해석의 결과를 무한사면 해석에 적용하여 안전율을 계산하였다. 제안된 확률론적 해석법은 강우의 침투에 따른 사면의 시간 의존적 파괴확률을 계산할 수 있다.

Keywords

References

  1. Carsel, R. F. and Parrish, R. S. (1988), "Developing Joint Probability Distributions of Soil Water Retention Characteristics", Water Resources Research, Vol.24, pp.755-769. https://doi.org/10.1029/WR024i005p00755
  2. Chen, L. and Young, M. H. (2006), "Green-Ampt Infiltration Model for Sloping Surface", Water Resources Research, Vol.42, W07420.
  3. Cho, S. E. (2014), "Probabilistic Stability Analysis of Rainfallinduced Landslides Considering Spatial Variability of Permeability", Engineering Geology, Vol.171, pp.11-20. https://doi.org/10.1016/j.enggeo.2013.12.015
  4. Cho, S. E. (2015), "Surficial Stability Analysis by the Green-Ampt Infiltration Model with Bedrock Boundary Condition", Journal of Korean Society of Hazard Mitigation, Vol.15, No.1, pp.131-142. https://doi.org/10.9798/KOSHAM.2015.15.1.131
  5. Cho, S. E. (2017a), "Influence of Estimation of Hydraulic Conductivity Function on Rainfall Infiltration into Unsaturated Soil Slope", Journal of the Korean Geotechnical Society, Vol.33, No.9, pp.5-22. https://doi.org/10.7843/KGS.2017.33.9.5
  6. Cho, S. E. (2017b), "Prediction of Shallow Landslide by Surficial Stability Analysis Considering Rainfall Infiltration", Engineering Geology, Vol.231, pp.126-138. https://doi.org/10.1016/j.enggeo.2017.10.018
  7. 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
  8. Cho, S. E. and Lee, S. R. (2002), "Evaluation of Surficial Stability for Homogeneous Slopes Considering Rainfall Characteristics", Journal of Geotechnical and Geoenvironmental Engineering, Vol.128, No.9, pp.756-763. https://doi.org/10.1061/(ASCE)1090-0241(2002)128:9(756)
  9. Dou, H. Q., Han, T. C., Gong, X. N., and Zhang, J. (2014), "Probabilistic Slope Stability Analysis Considering the Variability of Hydraulic Conductivity under Rainfall Infiltration-redistribution Conditions", Engineering Geology, Vol.183, pp.1-13. https://doi.org/10.1016/j.enggeo.2014.09.005
  10. Green, W. H. and Ampt, G. A. (1911), "Studies of Soil Physics I-the Flow of Air and Water through Soils", Journal of Agriculture Science, Vol.4, No.1, pp.1-24. https://doi.org/10.1017/S0021859600001441
  11. Jeon, K. H., Lee, S. R., and Kim, Y. T. (2012), "Probabilistic Characteristics Soil-water Characteristic Curve of Unsaturated Weathered Granite-soil", Journal of Korean Society of Hazard Mitigation, Vol.12, No.3, pp.133-139. https://doi.org/10.9798/KOSHAM.2012.12.3.133
  12. Jeon, K. H., Lee, S. R., Yoon, S., and Kim, Y. T. (2013), "Slope Stability Analysis Based on Probabilistic Characteristics of Unsaturated Soil Properties of Weathered Granite Soil", Journal of Korean Society of Hazard Mitigation, Vol.13, No.1, pp.161-168. https://doi.org/10.9798/KOSHAM.2013.13.1.161
  13. Jeong, S. S., Choi, J. Y., and Lee, J. H. (2009), "Stability Analysis of Unsaturated Weathered Soil Slopes Considering Rainfall Duration", Journal of KSCE, Vol.29, No.1C, pp.1-9.
  14. Kim, J. H., Jeong, S. S., and Bae, D. H. (2013), "Predicting Rainfall Infiltration-Groundwater Flow based on GIS for a Landslide Analysis", Journal of the Korean Geotechnical Society, Vol.29, No.7, pp. 75-89. https://doi.org/10.7843/kgs.2013.29.7.75
  15. Kim, S. K. (1994), "Landslides in Korea", Proceedings of the North-East Asia Symposium and Field Workshop on Landslides and Debris Flows, Seoul, Korea, pp.75-99.
  16. Lu, N. and Godt, J. (2008), "Infinite Slope Stability under Steady Unsaturated Seepage Conditions", Water Resources Research, Vol.44, No.11, W11404. https://doi.org/10.1029/2008WR006976
  17. Lu, N. and Likos, W. J. (2006), "Suction Stress Characteristic Curve for Unsaturated Soil", Journal of Geotechnical and Geoenvironmental Engineering, Vol.132, No.2, pp.131-142. https://doi.org/10.1061/(ASCE)1090-0241(2006)132:2(131)
  18. Mein, R. G. and Farrel, D. A. (1974), "Determination of Wetting Front Suction in the Green-Ampt Equation", Soil Science Society of America Proc., Vol.38, pp.872-876. https://doi.org/10.2136/sssaj1974.03615995003800060014x
  19. Mein, R. G. and Larson, C. L. (1973), "Modeling Infiltration during a Steady Rain", Water Resources Research, Vol.9, No.2, pp.384-394. https://doi.org/10.1029/WR009i002p00384
  20. 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
  21. Phoon, K. K., Santoso, A., and Quek, S. T. (2010), "Probabilistic Analysis of Soil-water Characteristic Curves", Journal of Geotechnical and Geoenvironmental Engineering, Vol.136, No.3, pp.445-455. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000222
  22. Pradel, D. and Raad, G. (1993), "Effect of Permeability on Surficial Stability of Homogeneous Slopes", Journal of Geotechnical and Geoenvironmental Engineering, Vol.119, No.2, pp.315-332. https://doi.org/10.1061/(ASCE)0733-9410(1993)119:2(315)
  23. 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
  24. Sillers, W. C. and Fredlund D. G. (2001), "Statistical Assessment of Soil-water Characteristic Curve Models for Geotechnical Engineering", Canadian Geotechnical Journal, Vol.38. pp.1297-1313. https://doi.org/10.1139/t01-066
  25. Srivastava, A., Sivakumar Babu, G. L., and Haldar, S. (2010), "Influence of Spatial Variability of Permeability Property on Steady State Seepage Flow and Slope Stability Analysis", Engineering Geology, Vol.110, No.3-4, pp.93-101. https://doi.org/10.1016/j.enggeo.2009.11.006
  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. Yoo, N. J., Park, B. S., Lee, M. W., and Lee, J. H. (2001), "Development of Probabilistic Model of Landslides Using Infinite Slope Stability Analysis", Journal of KSCE, Vol.21, No.1C, pp. 57-68.
  28. Yoon, S., Lee, S. R., Kim, Y. T., and Go, G. H. (2015), "Estimation of Saturated Hydraulic Conductivity of Korean Weathered Granite Soils Using a Regression Analysis", Geomechanics and Engineering, Vol.9, No.1, pp.101-113. https://doi.org/10.12989/gae.2015.9.1.101
  29. Zhang, J., Huang, H. W., Zhang, L. M., Zhu, H. H., and Shi, B. (2014), "Probabilistic Prediction of Rainfall-induced Slope Failure Using a Mechanics-based Model", Engineering Geology, Vol.168. pp.129-140. https://doi.org/10.1016/j.enggeo.2013.11.005
  30. Zhu, H., Zhang, L. M., Zhang, L. L., and Zhou, C. B. (2013), "Two-dimensional Probabilistic Infiltration Analysis with a Spatially Varying Permeability Function", Computers and Geotechnics, Vol.48, pp.249-259. https://doi.org/10.1016/j.compgeo.2012.07.010