한국지반공학회논문집 (Journal of the Korean Geotechnical Society)

한국지반공학회 (Korean Geotechnical Society)
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압축파와 전단파를 이용한 불포화토의 간극비 산정

Void Ratio Evaluation of Unsaturated Soils by Compressional and Shear Waves

  • 변용훈 (고려대학교 건축사회환경공학부) ;
  • 조세현 (고려대학교 건축사회환경공학부) ;
  • 윤형구 (대전대학교 지반방재공학과) ;
  • 추연욱 (한국과학기술원 건설 및 환경공학과) ;
  • 김동수 (한국과학기술원 건설 및 환경공학과) ;
  • 이종섭 (고려대학교 건축사회환경공학부)
  • Byun, Yong-Hoon (School of Civil, Environmental, and Architectural Engineering, Korea University) ;
  • Cho, Se-Hyun (School of Civil, Environmental, and Architectural Engineering, Korea University) ;
  • Yoon, Hyung-Koo (Department of Geotechnical Disaster Prevention Engineering, Deajeon University) ;
  • Choo, Yun-Wook (Department of civil and Environmental Engineering, KAIST) ;
  • Kim, Dong-Su (Department of civil and Environmental Engineering, KAIST) ;
  • Lee, Jong-Sub (School of Civil, Environmental, and Architectural Engineering, Korea University)
  • 투고 : 2011.11.25
  • 심사 : 2012.11.29
  • 발행 : 2012.12.31
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초록

지표 근처의 지반은 대부분이 불포화 상태로 이루어진다. 이러한 불포화토의 강성은 지반에 존재하는 물과 공기의 양에 영향을 받게 된다. 본 연구의 목적은 전단파와 압축파 신호를 이용하여, 불포화토가 가지는 특성을 파악하는 것이다. 인위적으로 지표 근처의 불포화토를 조성하기 위해 압력판 추출시험기를 사용하였으며, 모관흡수력 조절을 통해 포화도를 변화시키면서 각 포화단계에 따른 탄성파를 측정하였다. 전단파 속도의 측정을 위해 벤더엘리먼트가 사용되었고, 압축파 속도의 측정을 위해서 디스크엘리먼트가 사용되었다. 각각의 트랜스듀서는 실험을 위해 제작된 사각형의 구속셀 안쪽에 설치되었다. 균질한 크기의 모래시료와 세립분을 이용하여 불포화토를 조성하였다. 실험을 통해 모관흡수력 변화에 따른 시료의 포화도 변화를 관찰하고, 각 포화단계에 따른 전단파 속도와 압축파 속도를 산정하였다. 또한, 측정된 탄성파 속도를 바탕으로 탄성계수, 전단탄성계수 그리고 포아송비를 추정하였다. 탄성파를 이용하여 산정한 간극비와 부피측정에 근거한 간극비가 거의 유사한 것으로 나타났다. 본 논문에서 제시한 불포화토의 각 포화단계에 따른 탄성파 속도의 측정실험은 지표 근처의 불포화토가 지니는 특성을 파악하기 위한 매우 효과적인 방법이 될 수 있음을 보여준다.

Soils are commonly unsaturated in the near surface. The stiffness of soils is affected by the amount of air and water. The objective of this study is to evaluate the porosity of the unsaturated soils by using the elastic waves including compressional and shear waves. The elastic waves are measured at different degrees of saturation by controlling the matric suction. Thus, the unsaturated soils are characterized at different levels of the matric suction. Shear and compressional waves are measured by using the bender elements and the piezo disk elements, respectively. Both transducers are installed on the walls of the rectangular cell. The unsaturated soils are prepared by using uniform size sands and silts. Test results show that both compressional and shear wave velocities change according to the matric suction. The elastic modulus, the shear modulus, and the Poisson's ratio are estimated based on the measured elastic wave velocities. In addition, the void ratio of the unsaturated soils estimated using elastic wave velocities matches well with the volume based void ratio. This study demonstrates that the elastic waves can be effectively used for the characterization of unsaturated soils.

키워드

참고문헌

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피인용 문헌

  1. Estimation of Crack Density of Rock by Using Elastic Wave Velocity vol.14, pp.5, 2014, https://doi.org/10.9798/KOSHAM.2014.14.5.123