대한토목학회논문집 (KSCE Journal of Civil and Environmental Engineering Research)

  • 제35권5호
  • /
  • Pages.1073-1082
  • /
  • 2015
  • /
  • 1015-6348(pISSN)
  • /
  • 2799-9629(eISSN)
대한토목학회 (Korean Society of Civil Engeneers)
권호 표지
DOI QR코드

DOI QR Code

불포화토 사면 안정해석에서 선행강우의 영향에 관한 연구

Influence of Antecedent Rainfall in Stability Analysis of Unsaturated Soil Slope

  • 이영생 (경기대학교 토목공학과) ;
  • 윤승현 ((주)이산 토질부, 경기대학교 대학원 토목공학과)
  • 투고 : 2015.08.05
  • 심사 : 2015.08.17
  • 발행 : 2015.10.01
PDF 다운로드
⟨ 이전 논문 다음 논문 ⟩

초록

불포화토 사면 거동은 불포화토의 수리학적 특성 및 역학적 특성, 지반 투수계수, 지반 내 지층 구조, 강우조건 즉 강우강도, 강우패턴, 강우 지속시간, 선행강우 등의 영향을 받는다. 이와 같은 여러 요소 중 산사태는 사면 파괴 당시 강우조건보다 그 이전에 발생했던 선행강우의 영향을 크게 받는 것으로 알려져 있어 선행강우의 영향은 사면 안정성 해석에서 중요한 요소로 작용할 것으로 예상된다. 따라서 강우에 의한 산사태 발생을 예측하고 대책을 마련하기 위하여 선행강우에 따른 사면 내 모관흡수력 분포를 반드시 고려하여야 하며 이후에 발생한 강우특성을 반영하여 사면 안정성 검토를 수행하여야 할 것으로 판단된다. 본 연구의 경우 실트질 흙 함량 구성을 5%, 10%, 20%로 달리한 3가지 시료를 조성한 후 각각의 시료에 대하여 흙-함수특성곡선 시험을 수행하여 관련 매개변수들을 분석하였다. 한 달 동안의 선행강우 적용과 집중호우에 해당하는 12시간 동안의 강우가 지속적으로 내릴 때 불포화토 내 모관흡수력 분포 및 응력, 강도와 같은 역학적 특성 변화 등을 분석하고 사면안정 수치해석을 수행한 후 선행강우와 흙-함수특성곡선이 사면의 안정에 미치는 영향을 비교, 분석하였다.

The behavior of the unsaturated soil slope can be influenced by the various factors such as the hydraulic characteristics, the mechanical characteristics, the coefficient of conductivity, the stratifications, the rainfall conditions i.e. the rainfall intensity, the rainfall pattern, the duration time of the rainfall and the antecedent rainfall etc. It is known that the slope failure is influenced greatly by the antecedent rainfall rather than the rainfall condition at the failure time, so the antecedent rainfall is supposed to be a very important factor in slope stability analysis among these factors. To predict and to prevent the slope failure by the rainfall, the distribution of the matric suction by the antecedent rainfall must be considered first of all and the slope stability analysis should be carried out by considering the successive rainfall characteristics. In this research, 3 samples with different quantity (5%, 10%, 20%) of silts were prepared and the SWCC (Soil-water characteristic curve) tests were carried out and the associated parameters were analyzed. After analyzing the distribution of the matric suction and the change of the mechanical characteristics such as the stress and the strength when applying the antecedent rainfall for one month and the successive intensive rainfall for 12 hours, the slope stability analyses were carried out numerically. And the influence of the antecedent rainfall for one month and the SWCC on the stability of a slope were compared and analyzed.

키워드

참고문헌

  1. Brooks, R. H. and Corey, A. T. (1964). "Hydraulic properties of porous medium." Hydrology Paper, No. 3, p. 27.
  2. Cho, S. E. and Lee, S. R. (2000). "Slope stability analysis of unsaturated soil slopes due to rainfall infiltration." Jr. of the Korean Geotechnical Society, Vol. 16, No. 1, pp. 51-64 (in Korean).
  3. Cho, S. E. and Lee, S. R. (2001). "Instability of unsaturated soil slopes due to infiltration." Computers and Geotechnics, Vol. 28, pp. 185-208. https://doi.org/10.1016/S0266-352X(00)00027-6
  4. Fei, C. and Keizo, U. (2004). "Numerical analysis of rainfall effects on slope stability." International Journal of Geomechanics, Vol. 4, No. 2, pp. 69-78. https://doi.org/10.1061/(ASCE)1532-3641(2004)4:2(69)
  5. Fredlund, D. G. and Xing, A.(1994). "Equations for the soil-water characteristic curve." Canadian Geotechnical Journal, Vol. 31, pp. 521-532. https://doi.org/10.1139/t94-061
  6. Fredlund, D. G., Morgenstern, N. R. and Widger, R. A. (1978). "Shear strength of unsaturated soils." Canadian Geotechnical Journal, Vol. 15, No. 3, pp. 313-321. https://doi.org/10.1139/t78-029
  7. Fredlund, D. G., Vanapalli, S. K., Xing, A. and Pufahl, D. E. (1995). "Predicting the shear strength function for unsaturated soils using the soil-water characteristic curve." Unsaturated Soils, Alonso and Delage (eds), Balkema, pp. 63-69.
  8. Fredlund, D. G., Xing, A. and Shangyan, H. (1994). "Predicting the permeability 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. Fredlund, D. G., Rahardjo, H. and Fredlund, M. D. (2012). Unsa­turated Soil Mechanics in Engineering Practice, John Wiley and Sons.
  10. Gan, J., Fredlund, D. G. and Rahardjo, H. (1988). "Determination of the shear strength parameters of an saturated soil using the direct shear test." Canadian Geotechnical Journal, Vol. 25, No. 3, pp. 277-283.
  11. GEO-SLOPE International Ltd. (2007). "Computer program SEEP/W for finite element seepage analysis." User's guide.
  12. GTS NX Online Manual (2014). MIDAS Information Technology Co. Ltd., Available at: http://manual.midasuser.com/KR/GTS%20NX/150/GTX.htm (Accessed: January 10, 2015).
  13. Jeong, S. S., Choi, J. Y. and Lee, J. H. (2009). "Stability analysis of unsaturated weathered soil slopes considering rainfall duration." Jr. of the Korean Society of Civil Engineers, Vol. 29, No. 1, pp. 1-9 (in Korean).
  14. Kim, J. H., Jeong, S. S., Kim, Y. M. and Lee, K. W. (2013). "Proposal of design method for landslides considering antecedent rainfall and in-situ matric suction." Jr. of the Korean Geotechnical Society, Vol. 29, No. 12, pp. 11-24 (in Korean). https://doi.org/10.7843/kgs.2013.29.12.11
  15. Kim, J., Jeong, S. and Regueiro, R. A. (2012). "Instability of partially saturated soil slopes due to alteration of rainfall pattern." Engi­neering Geology, October, Vol. 147-148, pp. 28-36. https://doi.org/10.1016/j.enggeo.2012.07.005
  16. Kim, Y. M., Lee, K. W. and Kim, J. H. (2013). "Influence of soil characteristic and rainfall intensity on matric suction of unsaturated weathered soil slope." Jr. of the Korean Society of Civil Engineers, Vol. 33, No. 3, pp. 1017-1025 (in Korean). https://doi.org/10.12652/Ksce.2013.33.3.1017
  17. L'Heureux, J. S., Hoeg, K. and Hoydal, O. A. (2006). "Numerical analyses and field case study of slope subjected to rainfall." Unsaturated Soils, GSP No. 147, ASCE, pp. 2279-2290.
  18. Lee, S. J. (2004). Estimation of Unsaturated Shear Strength and Soil Water Characteristic Curve for Weathered Granite Soil, Ph.D. Thesis, Korea Advanced Institute of Science and Technology.
  19. 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." Jr. of the Korean Geotechnical Society, Vol. 25, No. 1, pp. 65-76 (in Korean).
  20. Leong, E. C. and Rahardjo, H. (1997a). "Review of soil-water characteristic curve equations." Jr. of Geot. and Geoenv. Eng., Vol. 123, No. 12, ASCE, pp. 1106-1117. https://doi.org/10.1061/(ASCE)1090-0241(1997)123:12(1106)
  21. Leong, E. C. and Rahardjo, H. (1997b). "Permeability functions for unsaturated soils." Jr. of Geot. and Geoenv. Eng., Vol. 123, No. 12, ASCE, pp. 1118-1126. https://doi.org/10.1061/(ASCE)1090-0241(1997)123:12(1118)
  22. Morris, P. H., Graham, J. and Williams, D. J. (1992). "Cracking in drying soils." Canadian Geotechnical Journal, Vol. 29, pp. 263-277. https://doi.org/10.1139/t92-030
  23. Rahardjo, H., Li, X. W., Toll, D. G. and Leong, E. C. (2001). "The effect of antecedent rainfall on slope stability." Geotechnical and Geological Engineering, Vol. 19, No. 3/4, pp. 371-399. https://doi.org/10.1023/A:1013129725263
  24. Tsaparas, I., Rahardjo, H., Toll, D. G. and Leong, E. C. (2002). "Controlling parameters for rainfall-induced landslides." Computers and Geotechnics, Vol. 29, pp. 1-27. https://doi.org/10.1016/S0266-352X(01)00019-2
  25. van Genuchten, M. T. (1980). "A closed-form equation for predicting the hydraulic conductivity of unsaturated soils." Soil Science Society of America Journal, Vol. 44, pp. 892-898. https://doi.org/10.2136/sssaj1980.03615995004400050002x
  26. Vanapalli, S. K. and Fredlund, D. G. (1999). "Empirical procedures to predict the shear strength of unsaturated soils." Proc. of the 11th Asian Regional Conf. on SMFE, Seoul, Korea, pp. 93-96.
  27. Vanapalli, S. K., Fredlund, D. G., Pufahl, D. E. and Clifton, A. W. (1996). "Model for the prediction of shear strength with respect to soil suction." Canadian Geotechnical Journal, Vol. 33, pp. 379-392. https://doi.org/10.1139/t96-060
  28. Wheeler, S. J. and Sivakumar, V. (1995). "An elasto-plastic critical state framework for unsaturated soil." Geotechnique, Vol. 45, No. 1, pp. 35-53. https://doi.org/10.1680/geot.1995.45.1.35
  29. Won, T. O. and Sai, K. V. (2010). "Influence of rain infiltration on the stability of compacted soil slopes." Computers and Geotechnics, Vol. 37, pp. 649-657. https://doi.org/10.1016/j.compgeo.2010.04.003
  30. Zhan, T. L. T. and Ng, W. W. (2004). "Analytical analysis of rainfall infiltration mechanism in unsaturated soils." Int. Jr. of Geomechanics, Vol. 4, No. 4, pp. 273-284. https://doi.org/10.1061/(ASCE)1532-3641(2004)4:4(273)
  31. 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, pp. 569-582. https://doi.org/10.1139/t04-006