Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
권호 표지
DOI QR코드

DOI QR Code

Evaluation of Consolidation Properties in Soft Soils Using Elastic and Electromagnetic Waves

전단파와 전자기파를 이용한 연약 지반의 실내 압밀 특성 평가

  • Lee, Chang-Ho (School of Civil and Environmental Engrg., Georgia Institute of Technology) ;
  • Yoon, Hyung-Koo (Department of Civil, Environmental, and Architectural Engrg., Korea Univ.) ;
  • Kim, Joon-Han (Department of Civil, Environmental, and Architectural Engrg., Korea Univ.) ;
  • Lee, Jong-Sub (Department of Civil, Environmental, and Architectural Engrg., Korea Univ.)
  • 이창호 (조지아공대 건축.사회환경공학과) ;
  • 윤형구 (고려대학교 건축.사회환경공학과) ;
  • 김준한 (고려대학교 건축.사회환경공학과) ;
  • 이종섭 (고려대학교 건축.사회환경공학과)
  • Published : 2008.08.31
Download PDF
⟨ Previous Next ⟩

Abstract

A new hybrid oedometer cell is designed and manufactured to investigate a behavior of soft soils by using elastic and electromagnetic waves during consolidation test. Bender elements, which generate and detect shear waves, are placed in the top cap and the bottom plate and mounted on the oedometer wall. Double wedge type electrical resistance probe, which measures local void ratio change, is positioned onto the top cap of the oedometer cell. The bender elements and the electrical resistance probe are anchored into a nylon set screw with epoxy resin. The nylon set screw with epoxy resin minimizes directly transmited elastic waves through the oedometer cell due to impedence mismatch and allows for easy replacement of defected bender elements and electrical resistance probe. Primary consolidation time can be estimated from the slope of electrical resistance versus log time curve and the evolution of shear wave velocity. The shear wave velocity can be used to assess inherent anisotropy when disturbance effects are minimized because particle alignment affects the shear wave velocity. The void ratios evaluated by the electrical resistance probe are similar to those by the settlement during consolidation. This study suggests that the shear wave velocity and the electrical resistance can provide complementary imformations to understand consolidation characteristics such as primary consolidation, anisotropy, and void ratio.

연약 지반의 거동 특성 평가를 위하여 전단파 속도와 전기저항을 측정할 수 있는 새로운 압밀셀을 개발하였다. 전단파의 발진과 수신을 위한 벤더엘리먼트는 압밀셀의 상 하부판 및 벽면에 설치하였다. 국부적인 간극비 변화를 평가하기 위하여 이중 쐐기 형식의 전기저항 탐침을 적용하였다. 벤더 엘리먼트와 전기저항 탐침은 나일론 재질의 스크류 안에 고정하였다. 나일론 재질의 스크류는 압밀셀과의 임피던스 차이로 인하여 압밀셀을 통한 파의 직접적 전달을 최소화하며, 고장난 벤더 엘리먼트와 전기저항 탐침을 쉽게 교환하게 해준다. 전기저항-대수 시간 곡선의 기울기 및 전단파 속도의 변화로부터 일차 압밀 시간을 평가하였다. 교란 효과가 적을 경우, 입자 배열은 전단파 속도에 영향을 미치며 이로부터 흙의 고유 이방성을 평가할 수 있었다. 압밀 실험동안 침하량으로 산정한 간극비와 전기저항으로부터 계산된 간극비는 거의 유사한 것으로 나타났다. 본 연구는 전단퐈 속도와 전기저항이 일차 압밀, 고유 이방성, 간극비 등 연약 지반의 압밀 특성 파악을 위한 보완적인 정보를 제공해 줌을 보여준다.

Keywords

References

  1. 이종섭, 이창호 (2006a), "벤더엘리먼트 시험의 원리와 고려사항", 한국지반공학회 논문집, 제 22권 5호, pp. 47-57
  2. 이종섭, 이창호 (2006b), "압밀, 토모그래피, 액상화시험에서 벤 더 엘리먼트의 적용", 한국지반공학회 논문집,제22권8호,pp.43-54
  3. 이창호,이종섭,윤형구,쭝훙꿍,조태현(2006),"응력유도 및 고유 이방성에 따른 전단파 속도 특성", 한국지반공학회논문집, 제 22권, 11호, pp.47-54
  4. Afifi, S. S. and Woods, R. D. (1971), "Long-term pressure effects on shear modulus of soils", Journal of the Soil Mechanics and Foundations Division, ASCE, 97(10), 1445-1460
  5. Aki, K. and Richards, P. G. (1980), Quantitative seismology: Theory and Method. W. H. Freeman and Company, 932p
  6. Anderson, D. G. and Stokoe, K. H. (1978), "Shear Modulus: a time-dependent soil property", Dynamic Geotechnical Testing, ASTM, STP 654, 66-90
  7. Archie, G. E. (1942), "The electrical resistance log as an aid in determining some reservoir characteristics", Transactions of the American Institute of Mining, Metallurgical, and Petroleum Engineers, 146, 54-62
  8. ASTM D2435-04 (2004), "Standard Test Method for One- Dimensional Consolidation Properties of Soils Using Incremental Loading", Annual Book of ASTM Standard, Vol. 04.08
  9. Cho, G. C., Lee, J. S., and Santamarina, J. C. (2004), "Spatial variability in soils: High resolution assessment with electrical needle probe", Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 130(8), 843-850 https://doi.org/10.1061/(ASCE)1090-0241(2004)130:8(843)
  10. Dyvik, R. and Madshus, C. (1985), "Lab measurements of Gmax using bender elements", Proc. ASCE Conference on Advances in the Art of Testing Soils under Cyclic Conditions, 186-196
  11. Fernandez, A. L. (2000), Tomographic imaging the state of stress. PhD thesis, Civil Engineering, Georgia Institute of Technology, Atlanta
  12. Hardin, B. O. and Black, W. L. (1968), "Vibration modulus of normally consolidated clay", Journal of the Soil Mechanics and Foundations Division, ASCE, 94(2), 353-369
  13. Ismail, M. A. and Rammah, K. I. (2006), "A new setup for measuring Go during laboratory compaction", Geotechnical Testing Journal, ASTM, 29(4), 280-288
  14. Klein, K. and Santamarina, J. C. (2005), "Soft sediments: wavebased characterization", International Journal of Geomechanics, ASCE, 5(2), 147-157 https://doi.org/10.1061/(ASCE)1532-3641(2005)5:2(147)
  15. Knox, D. P., Stokoe, K. H. II., and Kopperman, S. E. (1982), "Effect of state of stress on velocity of low-amplitude shear waves propagating along principal stress directions in dry sand", Geotechnical Engineering Report GR 82-23, University of Texas at Austin
  16. Lee, J. S. and Santamarina, J. C. (2005), "Bender elements: performance and signal interpretation", Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 131(9), 1063-1070 https://doi.org/10.1061/(ASCE)1090-0241(2005)131:9(1063)
  17. Lee, J. S. and Santamarina, J. C. (2006), Discussion "Measuring shear wave velocity using bender elements", by Leong, E.C., Yeo, S.H., and Rahardjo, H. Geotechnical Testing Journal, ASTM, 29, 439-441
  18. Lee, J. S., Fernandez, A. L., and Santamarina, J. C. (2005), "Swave velocity tomography: small-scale laboratory application." Geotechnical Testing Journal, ASTM, 28(4), 336-344
  19. Marcuson, W. F. and Wahls, H. E. (1972), "Time effects on dynamic shear modulus of clays", Journal of the Soil Mechanics and Foundations Division, ASCE, 98(12), 1359-1373
  20. Pennington, D. S., Nash, D. F. T., and Lings, M. L. (1997), "Anisotropy of Go shear stiffness in Gault Clay", Geotechnique, 47(3), 391-398 https://doi.org/10.1680/geot.1997.47.3.391
  21. Roesler, S. K. (1979), "Anisotropic shear modulus due to stress anisotropy", Journal of Geotechnical Engineering Division, ASCE, 105(7), 871-880
  22. Sanchez-Salinero, I., Roesset, J. M., and Stokoe, K. H. II. (1986), Analytical studies of body wave propagation and attenuation, Report GR-86-15, University of Texas, Austin. 272p
  23. Santamarina, J. C., Klein, K. A., and Fam, M. A. (2001), Soils and Waves - Particulate Materials Behavior, Characterization and Process Monitoring, John Wiley and Sons, New York
  24. Viggiani, G. and Atkinson, J. H. (1995), "Interpretation of bender element tests", Geotechnique, 45(1), 149-154 https://doi.org/10.1680/geot.1995.45.1.149
  25. Yamashita, S. and Suzuki, T. (2001), "Small strain stiffness on anisotropic consolidated state of sands by bender elements and cyclic loading tests", Proc. 15th International Conference of Soil Mechanics and Geotechnical Engineering, Istanbul, 325-328
  26. Yu, P. and Richart, F. E. Jr., (1984), "Stress ratio effects on shear modulus of dry sands", Journal of Geotechnical Engineering, ASCE, 110 (3), 331-345 https://doi.org/10.1061/(ASCE)0733-9410(1984)110:3(331)
  27. Zeng, X. and Grolewski, B. (2005), "Measurement of Gmax and estimation of Ko of saturated clay using bender elements in an oedometer", Geotechnical Testing Journal, ASTM, 28(3), 264- 274