Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Investigation of Pohang Earthquake Liquefaction Using 1D Effective-Stress Site Response Analysis

1차원 유효응력개념의 지반응답해석을 통한 포항지진의 액상화 현상 규명

  • Ahn, Jae-Kwang (Earthquake and Volcano Research Division, KMA) ;
  • Baek, Woo-Hyun (Dept. of Civil & Architecture Engrg., Seokyung Univ.) ;
  • Choi, Jae-Soon (Dept. of Civil & Architecture Engrg., Seokyung Univ.) ;
  • Kwak, Dong Youp (Dept. of Civil and Environmental Engrg., Hanyang Univ., ERICA)
  • 안재광 (기상청 지진화산연구과) ;
  • 백우현 (서경대학교 토목건축공학과) ;
  • 최재순 (서경대학교 토목공학과) ;
  • 곽동엽 (한양대학교 건설환경공학과)
  • Received : 2018.05.10
  • Accepted : 2018.08.06
  • Published : 2018.08.31
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Abstract

Since the observation of ground motions in South Korea, liquefaction manifestation was the first to be observed in Pohang earthquake in 2017 with $M_L$ 5.4. Because liquefaction causes ground settlement and lateral spread damaging in-ground or super structures, various researchers have been analyzing the Pohang liquefaction case history to better understand and predict liquefaction consequence and to prevent future disasters. In prior research at the 2018 EESK conference, a map of Liquefaction Potential Index (LPI), indicating the severity of liquefaction, in Pohang was created and compared with damage observations. The LPI correlated well with the observations, but the severity categorized by LPI range was significantly higher than the actual observations in most regions. The prior LPI map was created evaluating ground motions using the simplified approach. In this research, we perform the effective site response analyses with porewater pressure generation model for the detailed evaluation of liquefaction on the liquefied sites in Pohang. We found that the simplified approach for LPI evaluation can overestimate the severity.

지진에 의해 액상화 현상이 발생하면 지반의 침하 혹은 측방유동으로 지중 및 상부 구조물의 손상을 유발하기 때문에 이를 사전에 예측 대비하는 것이 매우 중요하다. 2017년 11월 15일에 발생한 $M_L=5.4$의 포항지진은 국내지진 관측이래 액상화 피해사례가 처음으로 접수되었으며 연구자들이 이에 대한 분석을 수행 중이다. 2018년 춘계 한국지진공학회에서 발표된 포항지역의 액상화 위험지도의 경우 지반조사 결과만을 활용하여 LPI(Liquefaction Potential Index)를 계산하고 대상지역의 피해를 추정하였다. 이때 보고된 결과에 따르면 포항지역이 전반적으로 액상화에 취약하며 상대적으로 위험해 보이는 지역은 실제 피해가 발생했던 지역과 유사하였다. 하지만 액상화 위험도는 실제 발생한 피해보다 과대 예측하였기에 액상화 피해수준 범위에 문제점이 제기되었다. 따라서 본 연구에서는 액상화 현상이 관측된 구간에서 1차원 지반응답해석을 수행하여 액상화 발생가능성을 분석하였다. 그 결과 지반분류에 따른 평가로부터 얻어진 LPI는 액상화 위험지도를 작성 시에 과대예측 할 수 있는 것으로 나타났다.

Keywords

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