Journal of the Korean GEO-environmental Society (한국지반환경공학회 논문집)

Korean Geo-Environmental Society (한국지반환경공학회)
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Liquefaction Assessment Variations with Regard to the Geotechnical Information Considering of Critical Depth for Liquefaction

액상화 취약심도를 고려한 지반정보에 따른 액상화 평가의 변화

  • Song, Sungwan (Department of Civil & Environmental Engineering, Dankook University) ;
  • Kim, Hansaem (Earthquake Research Center, Korea Institute of Geoscience and Mineral Resources) ;
  • Cho, Wanjei (Department of Civil & Environmental Engineering, Dankook University)
  • Received : 2020.02.20
  • Accepted : 2020.05.04
  • Published : 2020.06.01
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Abstract

Recently, due to the liquefaction caused by earthquakes in Pohang and surrounding areas, the importance of researches on the liquefaction assessment has increased. The possibility of liquefaction can be assessed using the geotechnical information. The cyclic resistance ratio (CRR) value used in the assessment of liquefaction can be determined by using the SPT-N values or shear wave velocity, Vs value. A study was conducted to compare the accuracy of the liquefaction assessment using these two types of geotechnical information, and concluded that the results using SPT-N values are more accurate than those using Vs values. The previous study speculated that the used Vs value was measured at a depth of 12 m uniformly without considering the critical depth of liquefaction. Therefore, 10 empirical equations that convert SPT-N values measured at critical depth of liquefaction into Vs values to confirm the validity of geotechnical information measured at 12 m points uniformly are used to assess the liquefaction possibility and the results were compared with the actual liquefaction results to confirm the accuracy. As a result, 7 out of 10 cases considering critical depth for liquefaction show higher accuracy than those not considered.

최근 포항 및 주변 지역에서 지진 발생에 따른 액상화 현상 관측으로 인해 액상화 발생 가능성을 예측하는 연구의 중요성이 대두되고 있다. 액상화 발생 가능성은 지반정보를 활용하여 평가할 수 있는데 평가에 활용되는 전단저항강도비(CRR)값은 두 가지 지반정보인 SPT-N값과 Vs값을 활용하여 결정할 수 있다. 이 두 가지 지반정보를 활용하여 평가한 액상화 발생 가능성의 정확도를 비교하는 연구가 수행된 바 있으며 해당 연구에서는 SPT-N값을 활용한 결과가 Vs값을 활용한 결과보다 정확하다는 결론을 지었다. 또한 Vs값을 활용한 결과의 정확도가 낮은 이유는 Vs값이 액상화에 취약한 심도를 고려하지 않고 일률적으로 12m 심도에서 측정되었기 때문인 것으로 판단하였다. 따라서 본 연구에서는 일률적으로 12m 지점에서 측정된 지반정보의 타당성을 확인하고자 액상화에 취약한 심도에서 측정된 SPT-N값을 Vs값으로 환산하는 총 10가지의 경험식을 활용하여 환산된 Vs값을 통해 액상화 발생 가능성을 평가하고 실제 액상화 발생 결과와 비교하여 정확도를 확인하는 작업을 수행하였다. 그 결과 액상화에 취약한 심도를 고려한 10가지 경우 중 7가지 경우에 대하여 고려하지 않은 결과에 비해 정확도가 높게 나타났다.

Keywords

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