Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Principles and Considerations of Bender Element Tests

벤더엘리먼트 시험의 원리와 고려사항

  • Lee Jong-Sub (Dept. of Civil and Environment Engrg., Korea Univ.) ;
  • Lee Chang-Ho (Dept. of Civil and Environment Engrg., Korea Univ.)
  • 이종섭 (고려대학교 사회환경시스템공학과) ;
  • 이창호 (고려대학교 사회환경시스템공학과)
  • Published : 2006.05.01
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Abstract

The shear wave velocity is related with the stiffness of granular skeleton and mass density. The shear stiffness of the granular skeleton remains unaffected by the presence of the fluid. Bender elements are convenient shear wave transducers for instrumenting soil cells due to optimal soil-transducer coupling. This study addresses the principles of the shear wave, the design and implementation of bender elements including electromagnetic coupling prevention, directivity, resonant frequency, detection of first arrival, and near field effects. It is shown that electromagnetic coupling effects can be minimized using parallel-type bender elements. Thus, the in-plane S-wave directivity is quasi-circular. The resonant frequency of bender element installations depends on the geometry of the bender element, the anchor efficiency and the soil stiffness. One of the most cumbersome parts in the bender element test is near field effects, which affect the selection of arrival time. The selection of the first arrival within the near field Is effectively solved by the multiple reflection technique and signal matching technique. Bender elements, which requires several considerations, may be effective tools for the subsurface characterization by using S-wave.

전단파는 흙 입자의 강성과 밀도에 연관된다. 흡 입자의 전단 강성은 물의 존재 여부에 영향을 받지 않는다. 벤더 엘리먼트는 흙과 트랜스듀서 간의 뛰어난 결합 효과를 보여 토질 시험 장치에 적용하기에 편리한 전단파 트랜스듀서이다. 본 논문은 전단파의 기본 원리를 살펴본 뒤, 전자기 커플링 방지, 지향성(directivity), 공진주파수, 초동 추정, 근접장 효과 등을 포함하여 벤더 엘리먼트의 설계와 설치에 대하여 다루었다. 전해질 용액 속에서의 전기적 간섭(cross-talk)현상은 병렬 타입의 벤더 엘리먼트를 사용함으로써 최소화할 수 있다. 캔틸레버 보 형식의 벤더 엘리먼트는 전단파의 지향성은 원형에 가깝게 나타났다. 벤더 엘리먼트의 공진주파수는 벤더 엘리먼트 자체의 특성, 흡의강성 및 엥커 특성에 의존적인 것으로 나타났다. 벤더 엘리멘트 시험에서 가장 어려운 부분 중의 하나는 전단파의 도착시간에 영향을 주는 근접장 효과이다. 근접장 내에서 전단파의 도착시간 산정은 다중반사법(multiple reflection method)과 signal matching 기술을 적용하여 해결할 수 있다. 여러 가지 고려사항이 요구되는 벤더 엘리먼트는 전단파를 이용한 지반 동적 특성 파악에 매우 효과적인 방법이 될 수 있을 것이다.

Keywords

References

  1. Abbiss, C. P. (1981), 'Shear wave measurements of the elasticity of the ground', Geotechnique, 31(1), 91-104 https://doi.org/10.1680/geot.1981.31.1.91
  2. Aki, K. and Richards, P. G. (1980), Quantitative seismology: Theory and Method. W. H. Freeman and Company, 932p
  3. Blewett, J., Blewett, I. J., and Woodward, P. K. (1999), 'Measurement of shear-wave velocity using phase-sensitive detection technique', Can. Geotech. J., 36(5), 934-939 https://doi.org/10.1139/cgj-36-5-934
  4. Blewett, J., Blewett, I. J., and Woodward, P. K. (2000), 'Phase and a,plitude responses associated with the measurement of shear-wave velocity in sand by bender elements', Can. Geotech. J., 37(6), 1348-1357 https://doi.org/10.1139/cgj-37-6-1348
  5. Brignoli, E. G. M., Gotti, M., and Stokoe, K. H. II. (1996), 'Measurement of shear waves in laboratory specimens by means of piezoelectric transducers', Geotech. Test. J., 19(4), 384-397 https://doi.org/10.1520/GTJ10716J
  6. Cruse, T. A. and Rizzo, F. J. (1968), 'A direct formulation and numerical solution of the general transient elastodynamic problem', J. Mathematical Analysis and Applications, 22, 244-259
  7. Dyvik, R. and Madshus, C. (1985), 'Lab measurements of $G_{max}$ using bender element', Proc. ASCE convention on Advances in the art of testing soils under cyclic conditions, 186-196
  8. Fam, M. A. and Santamarina, J. C. (1995), 'Study of geoprocesses with complementary wave measurements in an oedorneter', Geotech. Test. J., 19(4), 307-314
  9. Fernandez, A. L. (2000), Tomographic imaging the state of stress, Ph.D thesis, Civil Engineering, Georgia Institute of Technology, 298p
  10. Jovicic, V., Coop, M. R., and Simic, M. (1996), 'Objective criteria for determining Gmax from bender element tests', Geotechnique, 46(2), 357-362 https://doi.org/10.1680/geot.1996.46.2.357
  11. Jovicic, V. and Coop, M. R. (1997), 'Interpretation of bender element tests', Geotechnique, 47(3), 875
  12. Kawaguchi, T., Mitachi, T., and Shibuya, S. (2001), 'Evaluation of shear wave travel time in laboratory bender element test', Proc. 15th Int. Conf. on soil Mech. and Geotech. Eng, 155-158
  13. 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
  14. Lee, J. S. (2003), High resolution geophysical techniques for small-scale soil model testing, PhD Thesis, Georgia Institute of Technology, Atlanta, Georgia
  15. Lee, J.S., Fernandez, A.L., and Santamarina, J.C. (2005), 'S-wave velocity tomography: Small-scale laboratory application', Geotechnical Testing Journal, ASTM, 28(4), 336-344
  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. Lohani, T. N., Imai, G., and Shibuya, S. (1999), 'Determination of shear wave velocity in the bender element test', Earthquake Geotech. Eng., Seco e Pinto eds., Lisboa, Portugal, 101-106
  18. Mancuso, C., Simonelli, A. L., and Vinale, F. (1989), 'Numerical analysis of in situ S-wave measurement', Proc. 12th Int. Conf. on Soil Mech. and Found. Eng., Rio de Janeiro, Brazil, 277-280
  19. Meirovitch, L. (1967), Analytical Methods in Vibrations,' The Macmillan Company, 555p
  20. Roester, S. K. (1979), 'Anisotropic shear modulus due to stress anisotropy', J. Geotech. Eng., 105(7), pp.871-888
  21. Sanchez-Salinero, I., Rosset, 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
  22. Santamarina, J. C. and Fam, M. A. (1997), 'Interpretation of bender element tests -discussion', Geotechnique, 47(4), 873-875 https://doi.org/10.1680/geot.1997.47.4.873
  23. Santamarina, J. C., Klein, K. A., and Fam, M. A. (2001), Soils and WavesParticulate Materials Behavior, Characterization and Process Monitoring, John Wiley and Sons. New York, 488p
  24. Shirley, D. J. (1978), 'An improved shear wave transducer', J. Acoustical Society of America, 63(5), 1643-1645 https://doi.org/10.1121/1.381866
  25. Shirley, D. J. and Hampton, L. D. (1978), 'Shear wave measurements in laboratory sediments', J. Acoustical Society of America, 63(2), 607-613 https://doi.org/10.1121/1.381760
  26. Viggiani, G. and Atkinson, J. H. (1995a), 'Interpretation of bender element tests', Geotechnique, 45(1), 149-154 https://doi.org/10.1680/geot.1995.45.1.149
  27. Viggiani, G. and Atkinson, J. H. (1995b), 'Stiffness of fine-grained soil at very small strains', Geotechnique, 45(2), 249-265 https://doi.org/10.1680/geot.1995.45.2.249
  28. Woods, R. D. and Stokoe, K. H. II. (1985), 'Shalloe seismic exploration in soil dynamics', Proc. a session held in conjunction with the ASCE Convention, Woods, R. D. eds., Detroit, Michigan, 120-156
  29. Yu, P. and Richart, F. E. Jr. (1984), 'Stress ratio effects on shear modulus of dry sands', Journal of Geotechnical Engineering, Vol.110, No.3, pp.331-345 https://doi.org/10.1061/(ASCE)0733-9410(1984)110:3(331)