Journal of the Korean Geosynthetics Society (한국지반신소재학회논문집)

Korean Geosynthetics Society (한국지반신소재학회)
권호 표지
DOI QR코드

DOI QR Code

Evaluation of Strength Incremental Ratio of Korean Marine Clayey Soil

국내 해성 점성토의 강도증가율 평가

  • Kim, Ju-Hyun (Department of Civil Engineering, Dongshin University)
  • Received : 2017.08.28
  • Accepted : 2017.09.19
  • Published : 2017.09.30
Download PDF
⟨ Previous Next ⟩

Abstract

Applicability of Skempton's and Hansbo's equation for estimating strength incremental ratio of Korean marine clayey soil was analyzed. These empirical equations have been commonly applied to design soft ground improvement by, especially, staged loading method. Strength incremental ratios proposed by Skempton (1954, 1957) and Hansbo (1957) using field vane tests(FVTs), measured in Scandinavia depends on plasticity index and liquid limit. Although lean clay in Scandinavia can be classified as clay based on USCS, this soil contains no clay mineral because it was produced by the glacial grinding of rock, sometimes, called rock flour. On the contrary, plasticity indices of Korean marine clayey soils increase linearly with the percentage of clay fraction (% finer than $2{\mu}m$ by weight). Except for strength incremental ratios using $q_u/2$ values in the case of soils having a low plasticity, such as Incheon, Hwaseong and Gunsan soils, these values are in the range of 0.25 to 0.35, independently of the plasticity index, $I_p$.

국내 해성 점성토의 강도증가율 평가시, 흙의 물리적 특성인 소성지수 및 액성한계만을 이용해서 비교적 쉽게 구할 수 있으므로 연약 지반 설계 실무에서 폭넓게 적용되어온 경험식, Skempton(1954, 1957) 및 Hansbo(1957)의 적용성을 분석하였다. Scandinavia 반도지역의 해성 점성토 지반에서 수행된 현장베인시험(FVT) 결과를 이용하여 제안된 두 식은 소성지수와 점토 함유량의 비례관계를 나타내는 국내 지반 조건에서는 적용성이 떨어지므로, 압밀 및 강도 산정을 위한 역학시험을 통해서 강도증가율을 평가하는 것이 적절한 것으로 분석되었다. 일축압축강도 저평가 경향의 인천, 화성 및 군산 저소성 토질의 결과를 제외하면, 소성지수에 관계없이 국내 해성 점성토 지반의 강도증가율은 대략 0.25~0.35 사이에서 분포하는 것으로 나타났다.

Keywords

References

  1. ASTM D422 (1990), "Standard test method for particle-size analysis of soils", ASTM International, West Conshohocken, PA.
  2. ASTM D2487 (2000), "Standard practice for classification of soils for engineering purposes (Unified Soil Classification System)", ASTM International, West Conshohocken, PA.
  3. ASTM D4318 (2000), "Standard test methods for liquid limit, plastic limit and plasticity index of soils", ASTM International, West Conshohocken, PA.
  4. ASTM D2166 (2003), "Standard test method for unconfined compressive strength of cohesive soil", ASTM International, West Conshohocken, PA.
  5. ASTM D2578 (2003), "Standard test method for field vane shear test in cohesive soil", ASTM International, West Conshohocken, PA.
  6. Bjerrum, L. (1954), "Geotechnical properties of Norwegian marine clays", Geotechnique, Vol.4, pp.49-69. https://doi.org/10.1680/geot.1954.4.2.49
  7. Grozic, J. L. H., Lunne, T. and Pande, S. (2003), "An oedometer test study on the preconsolidation stress of glaciomarine clays", Canadian geotechnical Journal, Vol.40, pp.857-872. https://doi.org/10.1139/t03-043
  8. Hansbo, S. (1957), "A new approach to the determination of the shear strength of clay by the fall-cone test", Proc. Swedish Geotechnical Institute, No.14, pp.46.
  9. Hanzawa, H. (1983), "Three case studies for short term stability of soft clay deposits, Soils and Foundations, Japanese geotechnical society, Vol.23, No.2, pp.140-154. https://doi.org/10.3208/sandf1972.23.2_140
  10. Jamiolkowski, M., Ladd, C. C., Germaine, J. T. and Lancellotta, R. (1985), "New developments in field and laboratory testing of soils", Proc. of the XI ICSMFE, Vol.1, pp.57-163.
  11. Kim, S. J., Lee, S. D. and Kim, J. H. (2016), "Evaluation of undrained shear strength for clayey silt with low plasticity from the West coast", Journal of Korean Geotechnical Society, Vol.32, No.8, pp.15-25. https://doi.org/10.7843/KGS.2016.32.8.15
  12. Kim. J. H. (2017a), "Evaluation of CPTU cone factor of silty soil with low plasticity focusing on undrained shear strength characteristics", Journal of Korean Geosynthetics Society, Vol.16, No.1, pp.73-83. https://doi.org/10.12814/jkgss.2017.16.1.073
  13. Kim. J. H. (2017b), "Evaluation on partially drained strength of silty soil with low plasticity using CPTU data", Journal of Korean Geosynthetics Society, Vol.16, No.2, pp.55-66.
  14. Larsson, R. (1980), "Undrained shear strength in stability calculation of embankments and foundations on soft clays", Journal of Canadian Geotechnical Engineering, Vol.17, No.4, pp.591-602. https://doi.org/10.1139/t80-066
  15. La Rochelle, P. (1992), "personal communication".
  16. La Rochelle, P., Roy, M. and Tavenas, F. (1973), "Field measurements of cohesion in Champlain clays", Proc. 8th Int. Conf. on Soil Mechanics and Foundation engineering, Moscow, Vol.1, No.1, pp.229-236.
  17. Lee, K. J. and Im, J. C. (2007), "Strength increment rato of normally consolidated marine clay", Vol.27, No.4C, pp.269-278.
  18. Mikasa, M. (1967), "Presentation method of soil investigation results", Proc. of 11th Geotechnical symposium, JSSMFE, pp. 7-11.
  19. Mikasa, M. (1968), "Shear strength characterstics of diluvial clays found at hilly side of Osaka District", Proc. of the 2nd annual conference, JSSMFE, pp.111-116.
  20. Nash, D. F. T., Powell, J. J. M. and Lloyd, I. M. (1992), "Initial investigations of the soft clay test site at Bothkennar", Geotechnique, Vol.42, pp.163-181. https://doi.org/10.1680/geot.1992.42.2.163
  21. Schmertmann, J. H. and Morgenstern (1977), "Discussion of main session I, Proc. of the 9th ICSMFE, Vol.3, pp.356-360.
  22. Sim, J. R. (2015), "A study on the calculation technique of the shear strength of intermediate soils with low plasticity from western coastal areas", Ph. D thesis, Chonnam National University.
  23. Skempton, A. W. (1954), "The structure of inorganic soil, discussion", Proc. Soil Mechanics and Foundation Engineering, ASCE, Vol.8, separate No.478, pp.19-22.
  24. Skempton, A. W. (1957), "The planning and design of the new Hong Kong airport, Discussion", Proc. Inst. of Civil Engineers (London), Vol.7, pp.305-307.
  25. Tanaka. H. (1994), "Vane shear strength of a Japanese marine clay and applicability of Bjerrum's correction factor", Soils and Foundations, Japanese geotechnical society, Vol.34, No.3, pp.39-48. https://doi.org/10.3208/sandf1972.34.3_39
  26. Tanaka, H., Tanaka, M. and Shiwakoti, D. R. (2001), "Characteristics of soils with low plasticity: intermediate soil from Ishinomaki, Japan and lean clay from Drammen, Norway", Soils and Foundations, Japanese geotechnical society, Vol.41, No.1, pp.83-96. https://doi.org/10.3208/sandf.41.83