Journal of the Korean Geosynthetics Society (한국지반신소재학회논문집)

Korean Geosynthetics Society (한국지반신소재학회)
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Evaluation of the Depth of Improved Soil on Weathered Soil Slopes by Rainfall Duration

강우지속시간에 따른 풍화토사면의 개량토 심도 평가

  • Yu, Jin-Ju (Department of Civil Engineering, Daejin University) ;
  • Lee, Jong-Woo (Department of Civil Engineering, Daejin University) ;
  • Lee, Kang-Il (Department of Civil Engineering, Daejin University)
  • Received : 2022.05.04
  • Accepted : 2022.06.20
  • Published : 2022.06.30
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Abstract

Recently, irregular torrential rainfall have frequently occurred due to abnormal climate, and landslide damage is increasing. In Korea, more than 70% of the total land is mountainous areas, appropriate measures are needed to prevent landslides by heavy rainfall. When improved soil is applied to the surface of the slope, it is possible to suppress an increase in groundwater level due to rainfall penetration and secure stability of the slope. In this study, the appropriate depth of improved soil that can confirm the increase in groundwater level and secure stability by applying improved soil to the weathered soil slope was studied. A total of three cases were analyzed for the slope of the cross-section: standard slope for weathered soil (1:1.5, 1:1.8, and 1:2.0). For rainfall conditions, referring to the regional frequency probability rainfall provided by the Water resource Management Information System, the increase in groundwater level by stage was confirmed by assuming a 500-year frequency precipitation maximum duration of 48 hours. As a result of the study, in the case of natural slopes, the slope was completely saturated before 48 hours the rainfall duration, and there was a possibility of collapse. the improvement depth in the slope of 1:1.5 was appropriate for more than 1m from the surface regardless of the rainfall duration, and in the the slope of 1:1.8 was appropriate of 1m for more than 36 hours. in the slope of 1:2.0, it was appropriate for that safety when improved soil of 0.5m for rainfall duration 48 hours or more.

최근 기상이변으로 불규칙성의 집중호우가 자주 발생하여 산사태 피해가 늘어나고 있다. 우리나라의 경우 전체 토지의 70% 이상이 산지로 이루어져 있는 만큼, 집중강우 시 산사태를 예방할 수 있는 적절한 방안이 필요한 실정이다. 사면 표층부에 개량토를 적용할 경우 강우 침투로 인한 지하수위 상승을 억제하고 사면의 안정성을 확보할 수 있다. 본 연구에서는 풍화토사면에 개량토를 적용하여 지하수위 상승량을 확인하고 안정성을 확보할 수 있는 개량토 적절한 심도를 연구하였다. 해석단면의 경사는 풍화토지반에 대한 표준경사 대하여 총 3가지의 경우를 확인하였다(1:1.5, 1:1.8, 1:2.0). 강우 조건은 국가 수자원 관리 종합정보시스템에서 제공한 지역 빈도 확률강우량을 참고하여 500년 빈도 강수량 최대지속시간 48시간으로 가정하여 단계별 지하수위 상승량을 확인하였다. 연구결과, 자연사면의 경우 강우지속시간 48시간 이전에는 비탈면이 완전 포화되어 붕괴의 가능성이 있었다. 반면, 1:1.5 경사의 사면에서는 강우지속시간과 무관하게 지표면으로부터 1m 이상의 심도가 적절하며, 1:1.8 사면에서는 36시간 이상 지속 시에 1m의 심도가 적절한 것으로 평가되었다. 또한, 1:2.0 사면의 경우 48시간 이상 지속시에 0.5m 이상의 개량토를 적용하여야 안전성이 확보되는 것으로 나타났다.

Keywords

References

  1. Bhang, I. H. (2016), "A Study on the Behavior Characteristic of Composite Reinforced Earth with Improved Soil Surface and Geogrid-reinforced Backfill", Ph.D. Thesis, Graduate School of Jeonbuk National University.
  2. Bishop, A. W. and Bjerrum L. (1955), "The use of slip circle in the stability analysis of earth slopes", Geotechnique, Vol.5, No.1, pp.7-17. https://doi.org/10.1680/geot.1955.5.1.7
  3. Brand, E. W., Premchitt, H. B. and Phillipson, H. B. (1984), "Relationship between Rainfall and Landslides in HongKong", Proc. Of 4th Inter. SYMPOS. Landslides, Toronto, pp.377-384.
  4. Brooks, R. H. and Corey, A. T. (1964), "Hydraulic properties of porous media", Colorado State University Hydrology Paper, Vol.3, pp.27.
  5. Cho, S. E. and Lee, S. R. (2000), "Slope Stability Analysis of Unsaturated Soil Slopes Due to Rainfall Infiltration", Journal of the Korean Geotechnical Society, Vol.16, No.1, pp.51-64.
  6. Cho, H. K. (2020), "Verification and Status of Lightweight Aggregate based Coal Ash", Journal of the Korean Recycled Construction Resources Institute, Vol.15, No.1, pp.33-38.
  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", Geotechnicque, Vol.49, No.1, pp.1-3. https://doi.org/10.1680/geot.1999.49.1.1
  8. Fredlund, D. G., Xing, A. and Huang, S. (1994), "Predicting the Permeability Function for Unsaturated Soils usingthe Soil-Water Characteristic Curve", Canadian Geotechnical Journal, Vol.31, pp.533-546. https://doi.org/10.1139/t94-062
  9. Kim, J. H., Park, S. W., Jeong, S. S. and Yoo, J. H. (2002), "A Study of Stability Analysis on Unsaturated Weathered Slopes Based on Rainfall-induced Wetting", Journal of Korean Geotechnical Society, Vol.18, No.2, pp.123-136.
  10. Kim, S. K., Ryu, J. H. and Kim, D. H. (1999), "Infiltration Characteristics of Unsaturated Decomposed Soils", Journal of Civil Engineering, Vol.19, No.III-5, pp.995-1002.
  11. Lee, K. I., Park, S. B. and Choi, M. J. (2021), "Evaluation of Field Applicability of Slope of Improved Soil for Ground Stabilizer", Journal of the Korean Geosynthetics Society, Vol.20, No.2, pp.35-44. https://doi.org/10.12814/JKGSS.2021.20.2.035
  12. Lee, S. J. and Lee, S. R. (2005), "Soil Water Characteristic Curve for Weathered Granite Soils - A Prediction Method", Journal of the Korean geotechnical society, Vol.21, No.2, pp.17-26.
  13. Lee, Y. S., Lee, H. J. and Kim, Y. S. (2002), "Soil Water Characteristic Curve for Weathered Granite Soils - A Prediction Method", Journal of the Korean Geo-Environmental Society, Vol.3, No.2, pp.22-23.
  14. Lee, H. K. and Lee, I. (2009), "A Study for Unsatruated-Character of Weathered Granite Soil in Korea", Journal of the Korean Geo-Environmental Society, Vol.10, No.3, pp.13-20.
  15. Lumb, P. (1975), "Slope Failures in Hong Kong", Quartly Journal of Engineering Geology, Vol.8, pp.31-65. https://doi.org/10.1144/GSL.QJEG.1975.008.01.02
  16. Ministry of Land (2016), "Construction of Slope Design Criteria Guideline".
  17. Ryu, C. H. (2003), "Estimation of Slope Stability during the Change of Matric Suction", Journal of Civil and Environmental Engineering, Vol.2003, No.23, pp.195-201.
  18. Song, Y. S. (2003), "The design methods of the slopes reinforced by earth retention system", Ph.D. Thesis, Graduate School of Daejin University.
  19. Terzaghi, K. and Peck, R. B. (1967), "Soil Mechanics in Engineering Practice 2nd Edition", New York, John Wiley.
  20. Terzaghi, K. (1950), "Mechanisms of Landslides," Geotechnical Society of America, Berkeley, pp.83-125.
  21. Van Genuchten, M. T. (1980), "A closed form equation for predicting hydraulic conductivity in unsaturated soils", Soil Sci. Soc.Am. J., Vol.44, pp.892-898. https://doi.org/10.2136/sssaj1980.03615995004400050002x
  22. Water Resources Management Information System (2019), "Probability rainfall (regional frequency analysis)".