Journal of the Earthquake Engineering Society of Korea (한국지진공학회논문집)

Earthquake Engineering Society of Korea (한국지진공학회)
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LPI-based Assessment of Liquefaction Potential on the West Coastal Region of Korea

액상화 가능 지수를 이용한 국내 서해안 지역의 액상화 평가

  • 서민우 (일리노이주립대학교 토목환경공학과) ;
  • 선창국 (한국지질자원연구원 지진연구센터) ;
  • 오명학 (한국해양연구원 연안개발.에너지연구부)
  • Published : 2009.08.31
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Abstract

Liquefaction is a significant threat to structures on loose saturated sandy soil deposits in the event of an earthquake, and can often cause catastrophic damage, economic loss, and loss of life. Nevertheless, the Korean peninsula has for a long time been recognized as a safe region with respect to the hazard of liquefaction, as the peninsula is located in a moderate seismicity region, and there have been no reports of liquefaction, with the exception of references in some historical documents. However, some earthquakes that have recently occurred in different parts of the world have led to liquefaction in non-plastic silty soils, a soil type that can be found in many of the western coastal areas of Korea. In this study, we first present procedures for evaluating the liquefaction potential, and calculate the liquefaction potential index (LPI) distribution at two western coastal sites using both piezocone penetration test (CPTu) data and standard penetration test (SPT) data. The LPI is computed by integrating liquefaction potential over a depth of 20m, and provides an estimate of liquefaction-related surface damage. In addition, we compared the LPI values obtained from CPTu and SPT, respectively. Our research found that the CRR values from CPTu were lower than those from the SPT, particularly in the range between 40 and 120 for the corrected tip resistance, (qc1N)CS, from the CPTu, or in the range of CRR less than 0.23, resulting in relatively high LPI values. Moreover, it was observed that the differences in the CRR between the two methods were relatively higher for soils with high fine contents.

느슨한 포화 사질토 층에 위치한 구조물은 지진 시 액상화로 인해 막대한 인적 경제적 피해가 발생하기 때문에 액상화 발생 가능 지반으로 분류된 지역은 구조물의 설계 및 운영 시 액상화 발생 가능성에 주의를 기울어야 한다. 한반도의 경우 중진 지역에 해당되고 역사 문헌의 발생 기록을 제외한 어떤 액상화 피해도 보고되지 않음에 따라 오랫동안 액상화에 대해서는 안전지대로 여겨져 왔다. 하지만, 최근 해외 지진 사례에 의하면 국내 서해안 지역 지반과 유사한 비소성 실트질 흙에서의 액상화 발생과 이로 인한 피해 사례가 종종 보고되고 있다. 본 연구에서는 국내에서의 액상화 가능성 평가 기법 합리화의 일환으로 서해안 두 부지를 대상으로 피에조콘 관입시험(CPTu)과 표준관입시험(SPT) 결과를 이용하여 액상화가능지수(LPI)를 산정하였다. LPI는 심도 20m까지의 액상화 가능성을 통합 적분하여 액상화로 인한 지표면 피해 발생 정도를 지수로 제시한다. 먼저 대상 현장에 대해 시나리오별 액상화 발생 가능성을 평가한 후, CPTu와 SPT로부터 산정된 LPI 값을 비교하였다. 액상화 저항 강도를 의미하는 진동저항응력비(CRR) 값에 의하면, CPTu로부터 구한 보정 콘 선단저항력 (qc1N)CS가 40에서 120 사이인 경우 또는 CRR이 0.23 이하인 경우에 SPT로부터의 산정된 값보다 작게 평가되었다. 또한 CRR 차이는 세립질 함유량이 큰 흙에서 두 방법 간의 차이가 더 크게 나타났다.

Keywords

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