초록

얕은사면 파괴는 지표로 침투하는 강우에 의해 주로 발생한다. 이는 지표수의 침투시 모관흡수력의 감소에 의한 포화깊이 증가에 의해 발생한다. 본 연구에서는 국내의 전형적인 화강풍화토를 대상으로 강우시 사면에서의 습윤영향을 분석하였다. 이를 위하여 filter paper와 tensiometer 실험을 수행하여 함수특성곡선을 산정하였으며, 그에 따른 함수특성곡선의 방정식을 추정하였으며, 기존에 사용되고 있는 Green & Ampt의 포화 깊이 추정식과 수치해석결과를 비교 분석하였다. 본 연구 결과, Green & Ampt모델에 의한 이론 해는 포화깊이를 과소 추정하였으며, 포화깊이가 증가함에 따라 사면안전율은 감소하는 것으로 나타났다. 특히 포화깊이가 약 1.2m이상부터 사면안전율은 현저하게 감소하는 것으로 나타났다.

Abstract

Surface failures of slopes in weathered soil are caused by infiltration due to prolonged rainfall. These failures are mainly triggered by the deepening of the wetting band accompanied by a decrease in suction induced by the infiltrating water. This paper reports trends of rainfall-induced wetting band depth in two types of weathered soils that are commonly found in Korea. Both theoretical and numerical analyses are presented based on the soil-water characteristic curve (SWCC) obtained using filter paper as well as tensiometer tests. It is found that the magnitude of wetting front suction plays a key role in the stability of slopes in weathered soils. Theoretical analysis based on modified Green and Ampt model tends to underestimate the wetting band depth for typical Korean weathered soils. It was also deduced that for Korean weathered soils, the factor of safety drops rapidly once the wetting band depth of 1.2 m is reached.

주제어

#Infiltration   #Rainfall   #Slope stability   #Unsaturated soils   #Wetting front suction  

참고문헌 (23)

1. Chow, V. T., Maidment, D. R. and Mays, L. W. (1988), Applied Hydrology, McGraw-Hill, New York 
2. Lee, S. G. and de Freitas. M. H. (1989), 'A revision of the description and classification of weathered granite and its appli-cation to granites in Korea', J. of Engrg. Geol., Vol.22, No.1, pp.31-48 
3. Leong, E.C., He, L. and Rahardjo, H. (2002), 'Factors affecting the filter paper method for total and matric suction measurements', Geotechnical Testing Journal, Vol.25, No.3, pp.1-12 
4. 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 
5. Van Genuchten, M. T. (1980), 'A closed-form equation for predicting the hydraulic conductivity of unsaturated soils', J. Soil Sci. Soc. Am., Vol.44, pp.892-898 
6. ASTM (2000), Annual Book of ASTM Standards: Measurement of Soil Potential (Suction) Using Filter Paper. Vol.04.08, D5298-94, pp.154-159 
7. Fourie, A. B., Rowe, D. and Blight, G. E. (1999), 'The effect of infiltration on the stability of the slopes of a dry ash dump', Ge otechnique, Vol.49, No.1, pp.1-13 
8. Vanapalli, S. K., Fredlund, K. G., Pufahl, D. E. and Clifton, A. W. (1996), 'Model for prediction of shear strength with respect to matric suction', Canadian Geotechnical Journal, Vol.33, pp. 379-392 
9. Holtz, R.D. and Kovacs, W.D. (1981), An Introduction to Geotechnical Engineering, Prentice-Hall Inc, USA 
10. Rahardjo, H., Lim, T. T., Chang, M. F., and Fredlund, D. G. (1995), 'Shear-strength characteristics of a residual soil', Canadian Geotechnical Journal, Vol.32, pp.60-77 
11. Geo-Slope (1998), User's manual for SEEP/W and SLOPE/W: Version 4, Geo-Slope International Ltd, Canada. 
12. Leong, E. C. and Rahardjo, H. (1997), 'Review of Soil-Water Characteristic Curve Equations', Journal of Geotechnical and Geoenvironmental Engineering, Vol.123, No.12, pp.1106-1117 
13. Maidment, David R. (1993), Handbook of hydrology. David R. Maidment, McGraw-Hill, pp.5.32-5.51 
14. Moore, R. E. (1939), 'Water conduction from shallow water tables', Hilgardia, Vol.12, No.6, pp.383-426 
15. Green, W. H. and Ampt, G. A. (1911), 'Studies on soil physics. 1: The flow of air and water through soils', J. Agric. Sci., Vol.4, No.1, pp.1-24 
16. Pradel D. and Raad G. (1993), 'Effect of Permeability on Surficial Stability of Homogeneous Slopes', Journal of Geotechnical Engineering, Vol.119, No.2, pp.315-332 
17. Lumb, P. B. (1962), 'Effects of rain storms on slope stability', Symp. on Hong Kong Soils, Hong Kong, pp.73-87 
18. Rawls, W. J., Brakensiek, D. L. and Soni, B. (1983), 'Agricultural Management Effects on Soil Water Processes: Part I . Soil Water Retention and Green-Ampt Parameters. Trans', American Society of Agricultural Engineers, Vol.26, No,6, pp.1747-1752 
19. Fredlund, D. G. and Rahardjo, H. (1993), Soil Mechanics for Unsaturated Soils, John Wiley and Sons 
20. Skagg, R .W. and Khaleel, R. (1982), 'Hydrologic Modeling of Small Watersheds, Monograph 5', Infiltration. In C.T. Haan, ed. American Society of Agricultural Engineers, St. Joseph, Mich., pp.4-166 
21. Fredlund, D. G. and Xing, A. (1994), 'Equations for the soil-water characteristic curve', Canadian Geotechnical Journal, Vol.31, pp.521-532 
22. Kim, S. I., Park, C. H., Lee, S. R. and Jeong, S. S. (1994), Report of the Stability Analysis of Natural Slope of Yongseong Industrial Complex in Yeocheon, Lucky-Development Company, Korea 
23. Lumb, P. B. (1975), 'Slope failures in Hong Kong', Q. J. Engng Geol, Vol.8, pp.31-65 

이 논문을 인용한 문헌 (2)

1. Cho, Hong-Je ; Moon, Jong-Kyu ; Lee, Kwang-Je 2010. "Design of Absorption Pipe for Slope Stability" 韓國地盤工學會論文集 = Journal of the Korean geotechnical society, 26(11): 75~87  원문보기 상세보기
2. Kim, Jung-Hwan ; Jeong, Sang-Seom ; Bae, Deg-Hyo 2013. "Predicting Rainfall Infiltration-Groundwater Flow Based on GIS for a Landslide Analysis" 韓國地盤工學會論文集 = Journal of the Korean geotechnical society, 29(7): 75~89  원문보기 상세보기