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Research Article

The Influence of Fitting Parameters on the Soil-Water Characteristics Curve in Stability Analysis of an Unsaturated Natural Slope

불포화 자연사면의 안정해석시 흙-함수특성곡선 맞춤계수의 영향

Jae-Hong Kim1
,
Yong-Jae Yoo2
,
Young-Suk Song3*
김 재홍1
,
유 용재2
,
송 영석3*
1Professor, Department of Civil Engineering, Dongshin University
2Master’s Graduate, Department of Civil Engineering, Dongshin University
3Head of Geo-environmental Hazard Research Center, Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources
1동신대학교 토목환경공학과 교수
2동신대학교 토목환경공학과 석사졸업생
3한국지질자원연구원 지질환경연구본부 지질환경재해연구센터장
*Corresponding Author
30 June 2021. pp. 165-178
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Abstract

The influence of Soil-Water Characteristic Curve (SWCC) fitting parameters for an unsaturated natural slope was evaluated through seepage and slope stability analysis as a function of rainfall. Soil samples were collected from the study area in Jirisan National Park and the physical and mechanical characteristics of unsaturated soil layers were measured in laboratory tests. The saturation depth was calculated via seepage analysis by changing fitting parameters α, the parameter related to the Air Entry Value (AEV) and n, the parameter related to the slope of the SWCC in the range of natural conditions. Slope stability analysis using the limit equilibrium method considered the calculated depth of saturation. Results from seepage analysis for various rainfall conditions indicate the saturation depth in the soil layer suddenly increased as the fitting parameter α decreased; the saturation time for the entire soil layer also decreased. Slope stability analysis considering the calculated depth of saturation shows that the slope safety factor rapidly decreased as the fitting parameter α decreased, whereas the variation in slope safety factor was very small when n increased. Hence, fitting parameter α has a large effect on saturation depth during rainfall and therefore on slope stability, whereas slope stability is relatively unaffected by the fitting parameter n.

Keywords
Soil-Water Characteristic Curve
fitting parameter
seepage analysis
saturation depth
safety factor of slope
natural slope

자연사면을 대상으로 강우에 따른 침투해석 및 사면안정해석을 통하여 사면토층의 흙-함수특성곡선(SWCC) 맞춤계수에 따른 안정성의 영향을 평가하였다. 연구 대상사면의 토질시료를 채취하여 토층의 물리적, 역학적 및 불포화 특성을 실험하였다. 현장조건의 흙-함수특성곡선(SWCC)의 맞춤계수 α 및 n을 변화시켜 침투해석을 통한 포화심도를 산정하였으며, 이를 고려하여 한계평형해석기법을 이용한 사면안정해석을 수행하였다. 강우에 의한 침투해석 결과에 따르면 맞춤계수 α가 감소함에 따라 토층 내포화심도가 급격하게 증가하며, 전체 토층에 대한 포화시간도 짧아지는 것으로 나타났다. 그리고 포화심도를 고려한 사면안정해석결과에 의하면 맞춤계수 α가 감소함에 따라 사면안전율은 급격하게 감소하지만, 맞춤계수 n을 증가시키더라도 사면안전율의 변화는 매우 작은 것으로 나타났다. 따라서 강우침투로 인한 포화심도와 이를 고려한 사면안정성은 흙-함수특성곡선(SWCC)의 맞춤계수 α에 크게 영향을 받으며, 맞춤계수 n의 영향은 상대적으로 매우 작음을 알 수 있다.

키워드
흙-함수특성곡선
맞춤계수
포화깊이
사면안전율
자연사면
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Information
  • Publisher :Korean Society of Engineering Geology
  • Publisher(Ko) :대한지질공학회
  • Journal Title :The Journal of Engineering Geology
  • Journal Title(Ko) :지질공학
  • Volume : 31
  • No :2
  • Pages :165-178
  • Received Date : 2021-03-17
  • Accepted Date : 2021-05-24
  • DOI :https://doi.org/10.9720/kseg.2021.2.165
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