Complex Permittivity of Sand at Low Frequency

저주파수 영역에서 측정된 사질토의 유전특성

  • Oh Myoung Hak (Research Institute of Energy and Resources, Seoul National Univ.) ;
  • Kim Yong Sung (School of Civil, Urban & Geosystem Eng., Seoul National Univ.) ;
  • Park Jun Boum (School of Civil, Urban & Geosystem Eng., Seoul National Univ.) ;
  • Yoon Hyun Suk (Geotechnical Engrg. Research Dept., Korea Institute of Construction Technology(KICT))
  • Published : 2005.03.01

Abstract

This study was performed to identify the presence of measurement distortions such as electrode polarization and to investigate the influence of soil water content on complex permittivity at low frequency. In low frequency measurement using two-terminal electrode system, electrode polarization effect was observed at frequencies less than approximately 100 HBz. The analysis for real permittivity should be performed at frequencies above 100 kHz in order to exclude electrode polarization effect in the analysis of real permittivity at low frequency measurements. For a given soil, both of real and effective imaginary permittivity of wet soil increased continuously with volumetric water content. This is evidenced by the facts that the real permittivity is proportional to the number of dipole moments per unit volume and effective imaginary permittivity is effected by the conduction due to water. However, proportional relation between real permittivity and volumetric water content is valid at upper MHz frequencies.

본 연구에서는 저주파수 영역에서 유전상수 측정시 발생할 수 있는 왜곡효과를 규명하고, 함수비에 따른 사질토의 유전상수 변화를 실수부와 허수부를 구분하여 조사하였다. 축전기 형태의 셀에서 유전상수를 측정하는 경우 100kHz 이하의 주파수 영역에서 전극분극효과에 의하여 실제 매질의 유전상수보다 크게 측정되었기 때문에 전극 분극효과에 의한 영향을 배제하기 위해서는 100kHz 이상의 주파수에서 유전상수가 평가되어야 하는 것으로 판단되었다. 함수비에 따른 사질토의 유전상수를 평가한 결과 체적함수비 증가에 따라 연속적인 증가경향을 나타내었다. 이는 유전상수 실수부의 경우에는 사질토에서 발생하는 분극이 단위체적당 쌍극자 모멘트에 비례하기 때문이며, 유전상수 허수부의 경우에는 함수비 증가에 따른 전도손실량이 증가하기 때문이다. 그러나 유전상수 실수부에서의 체적함수비에 따른 증가경향은 공간전하분극의 영향이 크지 많은 1MHz 이상의 주파수 영역에서 유효한 것으로 나타났다.

Keywords

References

  1. Agilent Technologies (2000), Impedance Measurement Handbook, 2nd Ed., Agilent Technologies Co. Ltd
  2. ASTM D150 (1994), Standard test methods for AC loss characteristics and permittivity (dielectric constant) of solid electrical insulation, ASTM D150-94, Philadelphia
  3. Campbell, J. E. (1990), 'Dielectric properties and influence of conductivity in soils at one to fifty megahertz', Soil Science Society of American Journal, Vol.54, pp.332-341 https://doi.org/10.2136/sssaj1990.03615995005400020006x
  4. Carrier, M. and Saga, K. (1997), 'A four terminal measurement system for the investigation of the dielectric properties of clay at low frequencies', Geoenvironmental Engineering, Thomas Telford, London, pp.3-10
  5. Gross, G. W. and McGehee, R. M. (1988), 'The layered-capacitor method for bridge measurements of conductive dielectrics', IEEE Transactions on Electrical Insulation, Vol.23, pp.387-396 https://doi.org/10.1109/14.2379
  6. Hill, N. E., Vaughan, W. E., Price, A. H., and Davies, M. (1969), Dielectric properties and molecular behaviour, Van Nostrand Reinhold Company Ltd., U.K
  7. Kaya, A and Fang, H. Y. (1997), 'Identification of contaminated soils by dielectric constant and electrical conductivity', Journal of Environmental Engineering, ASCE, Vol.123, No.2, pp.169-177 https://doi.org/10.1061/(ASCE)0733-9372(1997)123:2(169)
  8. Klein, K. (1999), 'Electromagnetic properties of high specific surface minerals', Ph.D. thesis, Department of Civil Engineering, Georgia Institute of Technology, USA
  9. Klein, K. and Santamarina, J. C. (1997), 'Methods for broad-band dielectric permittivity measurements (soil-water mixtures, 5 Hz to 1.3 GHz)', Geotechnical Testing Journal, ASTM, Vol.20, No.2, pp.168-178 https://doi.org/10.1520/GTJ10736J
  10. Mitchell, J. K. and Arulanandan, K. (1968), 'Electrical dispersion in relation to soil structure', Journal of the Soil Mechanics and Foundations Division, ASCE, Vol.94, No.SM2, pp.447-471
  11. Rinaldi, V. A. and Cuestas, G. A. (2002), 'Ohmic conductivity of a compacted silty clay', Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol.128, No.10, pp.824-835 https://doi.org/10.1061/(ASCE)1090-0241(2002)128:10(824)
  12. Rinaldi, V. A. and Francisca, F. M. (1999), 'Impedance analysis of soil dielectric dispersion', Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol.125, No.2, pp.111-121 https://doi.org/10.1061/(ASCE)1090-0241(1999)125:2(111)
  13. Rinaldi, V. A. and Redolfi, E. R. (1996), 'The dielectric constant of soil-NAPL mixtures at low frequencies (100 Hz - 10 MHz)', Proceeding of Nonaqueous Phase Liquids (NAPLs) in the Subsurface Environment: Assessment and Remediation, ASCE, Washington D.C., pp.163-174
  14. Santamarina, J. C. (2001), Soils and Waves, John Wiley & Sons
  15. Santamarina, J. C. and Fam, M. (1997), 'Dielectric permittivity of soils mixed with organic and inorganic fluids (0.2 GHz to 1.30 GHz)', Journal of Environmental and Engineering Geophysics, Vol.2, No.1, pp.37-51 https://doi.org/10.4133/JEEG2.1.37
  16. Schwan, H. P. (1957), 'Electrical properties of tissues and cell suspensions', Biological and Medical Physics, 5
  17. Scott, J. H., Caroll, R. D., and Cunningham, D. R (1967), 'Dielectric constant and electrical conductivity measurements of moist rock: A new laboratory method', Journal of Geophysical Research, 72, pp.5101-5115 https://doi.org/10.1029/JZ072i020p05101
  18. Selig, E. T. and Mansukhani, S. (1975), 'Relationship of soil moisture to the dielectric property', Journal of the Geotechnical Engineering Division, ASCE, Vol.101, Vol.GT8, pp.755-770
  19. Shang, J. Q., Rowe, R. K., Umana, J. A, and Scholte, J. W. (1999), 'A complex permittivity measurement system for undisturbed/compacted soils', Geotechnical Testing Journal, ASTM, Vol.22, No.2, pp.159-168
  20. Shang, J. Q., Scholte, J. W., and Rowe, R. K. (2000), 'Multiple linear regression of complex permittivity of a till at frequency range from 200 MHz to 400 MHz', Subsurface Sensing Technologies and Applications, Vol.1, No.3, pp.337-356 https://doi.org/10.1023/A:1010199809583
  21. von Hippel, A. R. (1954), Dielectric Materials and Applications, von Hippel, A. R. ed., The Technology Press of Massachusetts Institute of Technology