KSCE Journal of Civil and Environmental Engineering Research (대한토목학회논문집)

Korean Society of Civil Engeneers (대한토목학회)
권호 표지
DOI QR코드

DOI QR Code

Anisotropic Elastic Shear Moduli of Sands Measured by Multi-directional Bender Element Tests in Stress Probe Experiments

사질토의 전단 하중 재하 시 다축 벤더엘리먼트 시험으로 구한 이방적 전단탄성계수

  • 고영주 ((주)포스코건설 토목환경사업본부) ;
  • 정영훈 (한국건설기술연구원 지하구조물연구실) ;
  • 이충현 (한국전력기술(주) 토목기술처) ;
  • 정충기 (서울대학교 건설환경공학부)
  • Received : 2007.10.22
  • Accepted : 2008.03.16
  • Published : 2008.05.31
Download PDF
⟨ Previous Next ⟩

Abstract

The stress-strain behavior of soils can usually be regarded as non-linear, while it is also known that the soil exhibits the linear-elastic behavior at pre-failure state (very small strain range, $<10^{-3}%$). This study aims to analyze the variation of anisotropic elastic shear moduli of granular soils in various stress conditions. The stress probe experiments with the triaxial testing device equipped with local strain gages and multi-directional bender elements were conducted. When the stress ratio exceeds the range between -0.5 and 1.5, the elastic shear stiffness in the axial direction deviates from the empirical correlation with current stresses, which indicates that the yielding of soils alters the internal pathway through which the elastic shear wave propagates. The experimental results show that the variation of elastic shear moduli in the horizontal direction closely relates to the volume change of soils.

흙은 변형률에 따라 강성이 감소하는 비선형적 변형 특성을 가지지만, 매우 작은 변형률 영역($<10^{-3}%$)에서는 선형탄성적 특성을 갖는다고 알려져 있다. 본 연구에서는 응력 경로 시험 중 실시한 다축 벤더엘리먼트 시험을 통해 다양한 응력 상태에서 사질토의 이방적 전단탄성계수를 측정하고, 그 변화를 분석하고자 하였다. 응력 경로 시험에서는 내부 변형률 측정 장치 및 3 방향의 벤더 엘리먼트가 부착된 삼축 시험기를 이용하였다. 전단 중 응력비가 -0.5~1.5의 범위를 벗어나게 되면 축 방향 전단탄성계수는 응력과의 경험적 상관관계와 차이가 발생하였고, 이로부터 시료의 항복이 전단파 전달 구조를 변화시킴을 알 수 있었다. 수평방향 전단탄성계수의 변화는 전단 중 체적 상태의 변화와 밀접한 관계가 있음을 알 수 있었다.

Keywords

References

  1. Burland, J. B. (1989) Ninth Laurits Bjerrum Memorial Lecture. 'Small is beautiful'. The stiffness of soils at small strains, Canadian Geotechnical Journal, Vol. 26, No. 4, pp. 499-516 https://doi.org/10.1139/t89-064
  2. Cascante, G. and Santamarina, J. C. (1996) Interparticle contact behavior and wave propagation, Journal of Geotechnical Engineering, ASCE, Vol. 122, No. 10, pp. 831-839 https://doi.org/10.1061/(ASCE)0733-9410(1996)122:10(831)
  3. Hardin, B. O. (1978) The nature of stress-strain behavior for soils, Earthquake Engineering and Soil Dynamics: Proc. ASCE Geotech. Div. Spec. Conf., Pasadena, Calif., pp. 3-90
  4. Hardin, B. O. and Black, W. L. (1966) Sand stiffness under various triaxial stresses, Journal of the Soil Mechanics and Foundations Division, ASCE, Vol. 92, No. 2, pp. 27-42
  5. Hardin, B. O. and Blandford, G. E. (1989) Elasticity of particulate materials, Journal of Geotechnical Engineering, ASCE, Vol. 115, No. 6, pp. 788-805 https://doi.org/10.1061/(ASCE)0733-9410(1989)115:6(788)
  6. Hoque, E. and Tatsuoka, F. (1998) Anisotropy in the elastic deformation of granular materials, Soils and Foundations, Vol. 38, No. 1, pp. 163-180 https://doi.org/10.3208/sandf.38.163
  7. Jardine, R. J. (1985) Investigations of Pile-soil Behavior, With Special Reference to the Foundations of Offshore Structures, Imperial College, University of London
  8. Jung, Y. H., Cho, W., and Finno, R. J. (2007) Defining yield from bender element measurements in triaxial stress probe experiments, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 133, No. 7, pp. 841-849 https://doi.org/10.1061/(ASCE)1090-0241(2007)133:7(841)
  9. Jung, Y. H. and Chung, C. K. (2008) Role of micromechanics features on stress-level dependency of cross-anisotropic elastic moduli in granular soils, Computers and Geotechnics, Vol. 35, No. 2, in press
  10. Kohata, Y., Tatsuoka, F., Wang, L., Jiang, G. L., Hoque, E., and Kodaka, T. (1997) Modelling the non-linear deformation properties of stiff geomaterials, Geotechnique, Vol. 47, No. 3, pp. 563-580 https://doi.org/10.1680/geot.1997.47.3.563
  11. Kuwano, R. and Jardine, R. J. (2002) On the applicability of crossanisotropic elasticity to granular materials at very small strains, Geotechnique, Vol. 52, No. 10, pp. 727-749 https://doi.org/10.1680/geot.2002.52.10.727
  12. Lee, J. S. and Santamarina, J. C. (2005) Bender elements: Performance and signal interpretation, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 131, No. 9, pp. 1063-1070 https://doi.org/10.1061/(ASCE)1090-0241(2005)131:9(1063)
  13. Leong, E. C., Yeo, S. H., and Rahardjo, H. (2005) Measuring shear wave velocity using bender elements, Geotechnical Testing Journal, Vol. 28, No. 5, pp. 488-498
  14. Viggiani, G. and Atkinson, J. H. (1995) Stiffness of fine-grained soil at very small strains, Geotechnique, Vol. 45, No. 2, pp. 249-265 https://doi.org/10.1680/geot.1995.45.2.249
  15. Wang, Y. H., Lo, K. F., Yan, W. M., and Dong, X. B. (2007) Measurement biases in the bender element test, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 133, No. 5, pp. 564-574 https://doi.org/10.1061/(ASCE)1090-0241(2007)133:5(564)
  16. Yimsiri, S. and Soga, K. (2000) Micromechanics-based stress-strain behaviour of soils at small strains, Geotechnique, Vol. 50, No. 5, pp. 559-571 https://doi.org/10.1680/geot.2000.50.5.559