Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Stiffness Characterization of Subgrade using Crosshole-Type Dynamic Cone Penetrometer

크로스홀 형태의 동적 콘 관입기를 이용한 노반의 강성특성 평가

  • Hong, Won-Taek (School of Civil, Environmental and Architectural Engrg., Korea Univ.) ;
  • Choi, Chan Yong (Advanced Infrastructure Research Team, Korea Railroad Research Institute) ;
  • Lim, Yujin (Dept. of Civil, Environmental and Railroad Engrg., Paichai Univ.) ;
  • Lee, Jong-Sub (School of Civil, Environmental and Architectural Engrg., Korea Univ.)
  • 홍원택 (고려대학교 건축사회환경공학부) ;
  • 최찬용 (한국철도기술연구원 선진인프라연구팀) ;
  • 임유진 (배재대학교 건설환경철도공학과) ;
  • 이종섭 (고려대학교 건축사회환경공학부)
  • Received : 2017.12.27
  • Accepted : 2018.02.06
  • Published : 2018.02.28
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Abstract

In order to support the load of the train with enough stiffness, a study on an effective method for the characterization of the stiffness of the compacted subgrade is required. In this study, the crosshole-type dynamic cone penetrometer (CDCP) is used for the stiffness characterization of the subgrade along the depth. For the application of the CDCP test, three points of compacted subgrades are selected as the study sites. For the study sites, CDCP test, in-situ density test, and light falling weight deflectometer (LFWD) test are conducted. As the results of CDCP tests, shear wave velocity profiles are obtained by using the travel times and the travel distances of the shear waves along the depth. In addition, maximum shear modulus ($G_{max}$) profiles are estimated by using the density of the subgrades and the shear wave velocity profiles. The averaged maximum shear moduli at each testing point are highly correlated with the dynamic deflection moduli ($E_{vd}$) determined by LFWD tests. Therefore, a reliable stiffness characterization of the subgrade can be conducted by using CDCP tests. In addition, because CDCP characterizes the stiffness of the subgrade along the depth rather than a representative value, CDCP test may be effectively used for the stiffness characterization of the subgrade.

열차의 하중을 적절한 강성으로 지지하기 위하여 다짐시공된 노반의 효과적인 강성특성 평가 기법에 대한 연구가 요구된다. 본 연구에서는 상부노반에 대하여 크로스홀 형태의 동적 콘 관입기(CDCP)를 적용함으로써 심도에 따른 강성특성을 평가하고자 하였다. CDCP의 적용을 위하여 세 단면의 다짐시공 완료된 상부노반이 대상 현장으로 선택되었으며, 각각의 개소에 대하여 CDCP 관입실험 및 들밀도시험, 동평판재하시험(LFWD)이 수행되었다. CDCP 관입실험 결과, 심도에 따른 탄성파 발신시간 및 전단파 수신시간을 획득하였으며, 이를 이용하여 노반의 전단파속도 주상도를 획득하였다. 또한, 동일 개소에서 들밀도시험으로부터 획득한 노반의 밀도 및 전단파속도 주상도를 이용하여 심도에 따른 최대전단강성계수($G_{max}$)를 평가할 수 있었다. CDCP 관입실험 및 들밀도시험으로부터 평가된 최대전단강성계수와 LFWD시험으로부터 획득한 동탄성계수($E_{vd}$)를 상호비교한 결과 매우 우수한 선형관계를 보이므로, CDCP 관입실험으로부터 유효한 강성특성을 평가할 수 있을 것이라 판단되었다. 또한, CDCP 관입실험으로부터 도출되는 결과는 일정 심도에 대한 대표 강성특성이 아닌 심도에 따른 연속적인 강성특성 이므로 노반의 강성특성 평가에 효과적으로 이용될 수 있을 것이라 기대된다.

Keywords

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