Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
권호 표지
DOI QR코드

DOI QR Code

Estimation of Unsaturated Permeability Function from Water Retention Characteristics for Korean Weathered Soils

함수특성에 근거한 국내 풍화토의 불포화 투수곡선 추정

  • Received : 2010.06.11
  • Accepted : 2010.10.04
  • Published : 2010.10.31
Download PDF
⟨ Previous Next ⟩

Abstract

Unsaturated permeability function is an important factor in the design and analysis of various unsaturated soil structures. Generally the permeability characteristics decrease as the mat ric suction increases and the trend is similar to water retention characteristics of a soil. The permeability of unsaturated soils can be obtained directly by laboratory tests or indirectly by estimation methods from other soil properties. For unsaturated soils sampled from 7 areas in KOREA, SWCCs and unsaturated permeability functions were obtained by experimental tests. The unsaturated permeability results were also compared with the unsaturated permeability functions derived from the SWCCs theoretically. However, the current estimation models of unsaturated permeability function did not express the unsaturated permeability characteristics. Therefore, the FXK-M permeability function was modified to predict more accurate permeability functions for Korean weathered soils using a correction factor that can be calculated from the air-entry value of SWCC. The new estimation model resulted in good agreements for all tested soils.

지반의 투수특성은 다양한 지반구조물의 설계 및 해석에서 중요한 지반물성이다. 특히 불포화 상태에서 모관흡수력의 영향을 받으며 모판흡수력 증가에 따라 감소하는 경향은 함수특성 변화와 유사하다. 불포화 투수계수는 실내실험을 통해 직접적으로 구하거나 함수특성곡선으로부터 유추된 이론식을 통해 간접적으로 얻을 수 있다. 본 논문에서는 국내 7개 지역에 대한 시료를 대상으로 함수특성실험과 본 연구에서 개발한 불포화 투수실험 장비를 이용하여 불포화 투수실험을 실시하였다. 지반의 함수상태를 나타내는 함수특성곡선이 불포화 투수계수와 밀접한 관련이 있으므로 함수특성곡선으로부터 불포화 투수곡선을 유추하는 여러 모텔 결과와 실험결과를 비교하였다. 그러나 기존의 추정방법은 국내지반의 투수특성을 잘 표현하지 못하고 있다. 따라서 국내 풍화토의 불포화 투수곡선을 정확히 유추하기 위하여 보정계수를 적용하여 FXK-M 투수모델을 제시하였고 보정계수를 함수특성곡선의 공기함입치로부터 산정할 수 있는 수식을 제안하였다.

Keywords

References

  1. 김상규, 류지협 (1996), "불포화토의 투수 및 강도특성 측정", 대한토목학회 학술발표회 논문집(III), pp.375-378.
  2. 김윤기 (2003), 투수시험결과 해석에 의한 불포화 풍화토의 투수성에 관한 연구, 석사학위논문, KAIST.
  3. 류태진, 임성윤 (2008), "불포화토의 투수계수분석 및 투수계수 방정식의 적용성 평가", 한국지반공학회논문집, Vol.24, No.1, pp.5-13.
  4. 최경림 (2007), 화강풍화토에 대한 함수특성곡선으로부터 불포화투수계수 유추에 관한 연구, 석사학위논문, KAIST.
  5. 황창수, 김태형 (2004), "불포화 투수계수함수에 대한 연구", 한국지반공학회논문집, Vol.20, No.3, pp.47-51.
  6. Ahuja, L. R., Naney, J. W., and Williams, R D. (1989), "Evaluation of Spacial Distribution of Hydraulic Conductivity Using Effective Porosity Data", Soil Science, Vol.148, No.6, pp.404-411. https://doi.org/10.1097/00010694-198912000-00002
  7. ASTM (2003), "Standard Test Methods for Measurement of Hydraulic Conductivity of Saturated Porous Materials Using a Flexible Wall Permeameter", D 5084.
  8. Barden, L., and Pavlakis, G. (1971), "Air and Water Permeability of Compacted Unsaturated Cohesive Soil", Journal of Soil Science, Vol.22, No.3, pp.302-318. https://doi.org/10.1111/j.1365-2389.1971.tb01618.x
  9. Brooks, R. H., and Corey, A. T. (1964), "Hydraulic properties of porous media", Colorado State University Hydrology Paper, Fort Collins, No. 3.
  10. Burdine, N. T. (1953), "Relative permeability calculations from poresize distribution data", Transactions of American Institute of Mining, Metallurgical, and Petroleum Engineers., Vol.198, pp.71-78.
  11. Campbell, J. D. (1973), Pore pressures and volume changes in unsaturated soils, Ph.D. Thesis, University of Illinois at Urbana-Champaign, Urbana-Champaign, IL.
  12. Fredlund, D. G., and Rahardjo, H. (1993), Soil mechanics for unsaturated soils, John Wiley & Sons, Inc., New York.
  13. Fredlund, D. G., and Xing, A. (1994), "A Equations for the soil-water characteristic curve", Canadian Geotechnical Journal, Vol. 31, No.3, pp.521-532.
  14. Fredlund, D. G., Xing, A., and Huang, S. (1994), "Predicting the permeability function for unsaturated soils using the soil-water characteristic curve", Canadian Geotechnical Journal, Vol.31, No.3, pp.533-546. https://doi.org/10.1139/t94-062
  15. Gardner, W. (1956), "Mathematics of isothermal water conduction in unsaturated soils", Highway Research Board Special Report 40 International Symposium on Physico-Chemical Phenomenon in Soils, pp.78-87.
  16. Hilf, J. W. (1956), An investigation of pore-water pressure in compacted cohesive soils, Ph. D. Thesis, Technical Memo No.654, U.S. Department of the Interior, Bureau of Reclamation, Design and Construction Devision, Denver.
  17. Huang, S., Fredlund, D. G., and Barbour, S. L. (1998), "Measurement of the coefficient of permeability for a deformable unsaturated soil using a triaxial permeameter", Canadian Geotechnical Journal, Vol.35, pp.426-432. https://doi.org/10.1139/t98-011
  18. Kunze, R. J., Uehara, G., and Graham, K. (1968), "Factors Important in the Calculation of Hydraulic Conductivity", Soil Science Society of America Proceedings, Vol.32, pp.760-765.
  19. Leong, E. C., and Rahardjo, H. (1997), "Review of soil-water characteristic curve equations", Journal of Geotechnical and Geoenvironmental Engineering, Vol.123, pp.1106-1117. https://doi.org/10.1061/(ASCE)1090-0241(1997)123:12(1106)
  20. Mualem, Y. (1976), "A New Model for Predicting the Hydraulic Conductivity of Unsaturated Porous Media", Water Resources Research, Vol.12, pp.593-622.
  21. Rawls, W. J.,and Brakensiek, D. L. (1985), "Prediction of soil water properties for hydrologic modeling", E. B. Jones and T. J. Ward (Eds.). Watershed Management in the Eighties., Proceedings of Symposium sponsored by Comm. on Watershed Management, I&D Division, ASCE, ASCE Convention, Denver, CO, April 30 May 1, pp.293-299.
  22. Schaap, M. G.., and Leij, F. J. (1998), "Using neural networks to predict soil water retention and soil hydraulic conductivity", Soil & Tillage Research, Vol.47, pp.37-42. https://doi.org/10.1016/S0167-1987(98)00070-1
  23. Sillers, W. S., Fredlund, D. G., and Zakerzadeh, No. (2001), "Mathematical attributes of som soil-water characteristic curve models", Geotechnical and Geological Engineering, Vol.19, pp. 243-283. https://doi.org/10.1023/A:1013109728218
  24. Soilmoisture Equipment Corporation (2005), "Volumetric Pressure Plate Extractor and Hysteresis Attachments", Operating Instruction manual, Santa Barbara, CA.
  25. van Genuchten, M.TH. (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. Vereecken, H., Maes, J., Feyen, J., and Darius, P. (1989), "Estimation the soil moisture retention characteristic from texture, bulk density, and carbon content", Soil Science, Vol.148, pp.389-403. https://doi.org/10.1097/00010694-198912000-00001