Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Profiling Stress History(OCR, $\sigma를$p) of Marine Clay Using Piezocone Penetration Test

해성점토지반에서 CPT를 이용한 응력이력(OCR, $\sigma$를 p)의 산정

  • 이강운 (㈜동성엔지니어링) ;
  • 윤길림 (한국해양연구원, 연안항만공학본부) ;
  • 채영수 (수원대학교 토목공학과)
  • Published : 2002.12.01
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Abstract

Various CPT-based prediction models far profiling stress history of marine clay at the southern part of the Korean peninsula were investigated by using both statistical analysis and case history study. Preconsolidation pressures($\sigma'$p) and overconsolidation ratio(OCR) estimated by empirical correlations and cone penetration tests were compared with those of laboratory odometer test results. Stress history of marine clay determined by odometer test results was in general overconsolidated at below 10m depth from the mudline, whereas marine clay at below l0m depth from the mudline which has an around 0.3 overconsolidation ratio showed variable stresses and unstable states. Preconsolidation pressures were computed by both empirical methods of the Chen and Mayne(1996) and theoretical method of Konrad and Law(1987). It is estimated that Chen and Mayne(1996)'s prediction method based on pore water pressure is more reliable than any other prediction methods, and their method proved to be the most reliable for overconsolidation ratio estimation. However, it is recommended that Mayne & Holtz(1988) and Mayne & Bachus(1988) methods are more suitable than any other methods for predicting the overconsolidation ratio at an underconsolidated (OCR<1) clay. For these reasons, rather than making use of existing prediction models, development of site specific empirical correlations which considers local characteristics and site conditions may be required due to different local stress history and variable soil properties.

국내 남해안 해성점토 지반의 응력이력(stress history)에 대하여 피조콘 관입시험 방법을 이용하여 통계분석과 사례 연구을 통하여 조사하였다. 경험식과 피조콘 관입시험으로 산정한 선행압밀응력과 과압밀비는 이론적, 경험적 상관관계를 찾고자 회귀분석을 수행하였고 기준값은 실내 표준압밀시험 결과를 토대로 하였다. 표준압밀시험에서 나타난 조사 지반의 응력이력 상태는 전체적으로 해수면 아래 표층 l0m까지는 과압밀된 상태였으나, 표층 l0m 아래 깊이에서는 과압밀비(OCR)가 0.3까지도 존재하여 전반적으로 지층상태는 불안정한 구조를 가지고 있었다. 응력이력에서 선행압밀하중의 결정은 Chen과 Mayne(1996)의 경험방법과 Konrad와 Law(1987)의 이론공식을 사용하였다. 산정결과, Chen과 Mayne(1996)의 경험공식중에서 간극수압을 이용한 예측방법이 가장 신뢰성이 높았다. 그리고 과압밀비도 Chen과 Mayne(1996)의 경험식이 가장 높은 신뢰성을 보였다. 하지만 Mayne과 Holtz(1988), 그리고 Mayne과 Bachus(1988)방법은 각각 OCR이 1.0이하인 미압밀 지반에서 좋은 결과를 제시하였다. 그러므로 피조콘 관입시험으로부터 지반의 응력이력을 산정하는 다양한 방법은 대부분 지반조건과 위치에 따라 그 결과가 크게 다르므로 지역과 현장특성을 반영한 적합식을 개발하여 지반 설계에 활용하는 것이 타당한 것으로 판단되었다.

Keywords

References

  1. Journal of the Geotechnical Engineering Division, ASCE v.106 no.4 Cone penetration in soil profiling Baligh, M. M.;Vivatrat, V.;Ladd, C. C.
  2. Proceedings of the 4th Canadian Conference on Marine Geotechnical Engineering, Memorial University, St. John's, Newfoundland v.1 Stress history profiling of marine clays by piezocone. Piezocone Brown, D. N.;Mayne, P. W.
  3. Canadian Geotechnical Journal v.28 no.2 Interpretation of overconsolidation ratio from in situ tests in recent clay deposits in Singapore and Malaysia Chang, M. F.
  4. CPT'95, International Symposium on Cone Penetration Testing Type 1 and 2 piezocone evaluation of overconsolidation ratio in clays Chen, B. S.;Mayne, P. W.
  5. Canadian Geotechnical Journal v.33 Statistical relationships between piezocone measurements and stress history of clays Chen, B. S. Y.;Mayne, P. W.
  6. Proceedings of the Geotechnology Conference on Penetration Testing in the U.K., Birmingham, 6-8 July Piezocone penetration test Houlsby, G. T.
  7. Geotechnique v.38 no.3 Discusion of Preconsolidation pressure form piezocone tests in marine clays Kabir, M. G.;Lutenegger, A. J.
  8. Geotechnique v.37 no.2 preconsolidation pressure from piezocone tests in marine clays Konrad, J. M.;Law, K.
  9. Report EL-68000, Electric Power Research Institute, EPRI Manual on estimating soil properties for foundation design Kulhawy, F. H.;Mayne, P. W.
  10. Proceedings, 9th International Conference on Soil Mechanics and Foundation Engineering v.2 Stress deformation and strength characteristics Ladd, C. C.;Foott, R.;Ishihara, K.;Schlosser, F.;Poulos, H. G.
  11. Swedish Geotechnical Institute Report No.42 Piezocone tests in clay Larsson, R.;Mulabdic, M.
  12. International Symposiumon cone penetration Testing Practical use of the piezocone in Eastern Canada clays. CPT'95 Leroueil, S.;Demers, D.;LaRochelle, P.; Martel G.;Virely, D.
  13. Proceedings of the ASCE Specialty Conference In Situ '86: Use of In-Situ Tests in Geotechnical Engineering no.6 CPT indexing of in situ OCR in clays Mayne, P. W.;S. P. Clemence(ed.)
  14. Soils and Foundations v.31 no.1 Determination of OCR in clays by piezocone tests using cavity expansion and critical state concepts Mayne, P. W.
  15. Proceedings of the 1st International Symposium on Penetrantion Testing(I.S.O.P.T.) v.2 Profiling OCR in clays by piezocone Mayne, P. W.;Bachus, R. C.;J. DeRuiter(ed.)
  16. Proceedings of the 13th International Conference On Soil Mechanics and Foundation Engineering v.1 Preliminary calibration of PCPT-OCR model for clays Mayne, P. W.;Chen, B. S. Y.
  17. Soils and Foundations v.28 no.1 Profiling stress history from piezocone soundings Mayne, P. W.;Holtz, R. D.
  18. Proceedings of the Geotechnology Conference on Penetration Testing in the U.K., Birmingham Interpretration and use of the piezocone test in UK clays Powell, J. J. M.;Quarterman, R. S. T.;Lunne T.
  19. Proceedings of the 2nd European Symposium on Penetration Testing, ESOPT-Ⅱ v.2 Strength and deformation parameters form cone penetration tests Senneset, K.;Janbu, N.;Svanφ, G.;A. Verruijt;F. L. Beringen;E. H. DeLeeuw
  20. Proceedings of the 7th European Conference on Soil Mechanics and Foundation Engineering v.1 Clay behaviour and the selection of design parameters Tavenas, F.;Leroueil, S.
  21. Proceedings of the International Symposium on Geotechnical Engineering of Soft Soils State-of-the-art on laboratory and in-site stress-strain-time behavior of soft clay Tavenas, F.;Leroueil, S.
  22. Geotechnique v.34 no.4 The interpretation of in-situ soil tests Wroth, C. P. https://doi.org/10.1680/geot.1984.34.4.449