Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Variation of Dielectric Constant of Sand due to Water Content and Measuring Frequency

수분함량과 측정주파수에 따른 사질토 지반의 유전상수 변화

  • 이주형 (한국건설기술연구원) ;
  • 오명학 (서울대학교 지구환경시스템공학부) ;
  • 박준범 (서울대학교 지구환경시스템공학부) ;
  • 김형석 (전자전기공학부)
  • Published : 2002.12.01
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Abstract

Dielectric constant measurement has drawn much attention in the investigation of the properties and contaminations of subsurface. In this study, by varying the frequency from 75 kHz to 12 MHz, dielectric constant was measured for the weathered granite soil and Jumunjin sand having different water contents and dry density. The dielectric constant of sand showed the dispersive behavior indicating that dielectric constant decreased with frequency of an electric field. And the dielectric constant of soil increased as water content and/or dry density increased due to the decrease of air portion and/or the increase of amount of water molecules which could contribute to the development of orientation polarization. The dielectric constant of sand showed a linear relationship with the moisture density, considering both water content and dry density. At low frequency, the dielectric constants calculated by Maxwell's, Topp's and CRIM equation deviated from measured values. It could be explained by the fact that those equations did not consider dispersive behavior of dielectric constant with the frequency.

최근 지반 특성과 지반 오염도의 조사를 위해 유전상수 측정기법을 적용하기 위한 연구가 활발히 진행되고 있다. 본 연구에서는 다양한 함수비와 건조단위중량을 갖는 화강풍화토와 주문진표준사의 유전상수를 75kHz～12MHz의 주파수 범위에서 측정하였다. 사질토의 유전상수는 주파수가 증가함에 따라 감소하는 분산거동을 보였다. 또한 함수 비나 건조단위중량이 증가함에 따라 배향분극에 기여하는 물분자의 양이 증가하고 유전상수가 1인 공기의 양이 감소하여 유전상수가 증가하였다. 흙의 유전특성은 함수비와 건조단위중량을 모두 고려한 수분밀도에 선형적으로 비례하는 경향을 나타내었다. Maxwell식, Topp식, CRIM식에 의한 계산값과 측정된 값을 비교한 결과 기존의 식은 유전상수의 분산거동을 고려하지 못하고 있기 때문에 저주파에서는 측정값과 차이를 나타내었다.

Keywords

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