Journal of the Korean Geosynthetics Society (한국지반신소재학회논문집)

Korean Geosynthetics Society (한국지반신소재학회)
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Assessment of Overconsolidation Ratio by Depth of Soft Ground: A Case Study in South Korea

국내 연약지반의 심도별 과압밀비 산정에 관한 사례연구

  • Lee, Jong-Young (Department of Civil and Environmental Engineering, Chung-Ang Univ.) ;
  • Han, Jung-Geun (Department of Civil&Environmental Engineering and Intelligent Energy&Industry, Chung-Ang Univ.)
  • Received : 2021.11.08
  • Accepted : 2021.11.11
  • Published : 2021.12.31
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Abstract

In this study, the overconsolidation ratio (OCR) of soft clay soil was calculated by conducting an indoor physical experiment and a dynamics test using undisturbed soil samples from a soft clay soil field in South Korea. The OCR by depth was predicted by comparing the experimental results with the existing empirical equations. Methods using the liquidity index and the existing empirical equation by the Naval Facilities Engineering Systems Command (NAVFAC) were examined, and the results were compared with the actual measured values. The method using the liquidity index was found to be suitable for estimating the rough OCR of the ground. However, the effect of drying was not considered for the ground above the groundwater level. Therefore, an equation for the correlation equation between the depth and OCR of each region, including the ground above the groundwater level, was proposed. The proposed equation was applied to the OCR prediction of the adjacent area. The predicted values in the area composed of clay (CL, CH) were found to be in good agreement with the actual values. In the region composed of silt (ML), however, the predicted values were not consistent with the actual values. This suggests that the sedimentation and compositional characteristics, rather than the engineering characteristics of the soil, are important factors that affect the OCR prediction.

본 연구에서는 국내 연약점토지반을 대상으로 현장에서 불교란 상태로 채취된 흙을 이용해 실내 물리실험 및 역학시험을 실시하여 OCR을 산정하였으며, 실험 결과를 이용해 기존의 경험식과 심도별로 OCR을 예측하였다. 액성지수와 NAVFAC의 경험식을 실제 측정값과 비교·검토한 결과 액성지수를 이용한 방법이 지반의 개략적인 OCR을 추정하기에 적절한 것으로 나타났으나 지하수위 상부 지반의 경우에는 건조로 인한 영향을 고려하지 못한 것으로 나타났다. 따라서 지하수위 상부지반을 포함한 각 지역별 심도-OCR간의 상관관계식을 제안하였으며, 제안된 식을 인접지역의 OCR 예측에 적용한 결과 점토(CL, CH)로 구성된 지역에서의 예측값은 실측값과 상당부분 일치하는 경향을 보였다. 그러나 실트(ML)로 구성된 지역에서는 예측값이 실제값과 불일치한 결과를 보여 흙의 공학적 특성보다는 퇴적 및 구성 특성이 OCR예측에 중요한 영향인자임을 확인할 수 있었다.

Keywords

Acknowledgement

This research was supported by the MSIT (Ministry of Science and ICT), Korea, under the ITRC (Information Technology Research Center) support program (IITP-2020- 2020-0-01655) supervised by the IITP (Institute of Information & Communications Technology Planning & Evaluation) and the National Research Foundation (NRF) of Korea, funded by the Korea government (MSIP) (NRF-2019R1 A2C2088962) and the Korea Agency for Infrastructure Technology Advancement under the Ministry of Land, Infrastructure and Transport of the Korean government (Project Number: 21CTAP-C164339-01).

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