한국지반공학회논문집 (Journal of the Korean Geotechnical Society)

  • 제36권3호
  • /
  • Pages.15-23
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  • 2020
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  • 1229-2427(pISSN)
  • /
  • 2288-646X(eISSN)
한국지반공학회 (Korean Geotechnical Society)
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얕은 심도 VS주상도를 활용한 VS30 예측 방법론 비교 및 최적 계수 제시

Comparison of Methods Predicting VS30 from Shallow VS Profiles and Suggestion of Optimized Coefficients

  • 최인혁 (한양대학교 대학원 건설환경시스템공학과) ;
  • 곽동엽 (한양대학교 공학대학 건설환경공학과)
  • 투고 : 2020.01.23
  • 심사 : 2020.03.10
  • 발행 : 2020.03.31
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초록

지표면에서의 지반운동을 예측하는 지반운동예측모델은 30m까지의 평균전단파속도인 VS30을 부지효과를 나타내는 주요한 변수로 사용한다. VS30은 만약 VS주상도 깊이(z)가 30m 이상이면 주상도로부터 바로 계산할 수 있다. 하지만, 모든 부지에서 z가 30m 까지 있는 것은 아니다. 따라서, z < 30m일 경우 30m까지 연장하는 모델로부터 VS30을 예측할 필요가 있다. 이번 연구에서는 국내 지반 환경에 맞게 z가 30m 미만인 부지에서 VS30을 추정하는 예측 모델에 대한 새로운 계수를 제안하였다. 분석 자료로 기상청과 국토지반정보 통합DB센터에서 획득한 297개의 VS주상도를 활용하였고, 선행연구에서 제안한 식의 계수들을 회귀분석을 통해 새롭게 제시하였다. 분석 결과, z ≥ 15m 일 경우 대수로그 잔차의 표준편차가 약 0.061이내이므로 신뢰성 높은 VS30를 예측하는 것으로 확인하였다. z < 15m 일 경우 σ가 계속 증가하며, z = 5m일 경우 σ = 0.1으로 나타났다. 따라서, 매우 얕은 심도의 VS주상도를 모델에 적용하는 경우 주의를 요하며, 가능하다면 30m깊이까지 지반조사를 실시하여 VS30을 계산하는 것을 추천한다.

Ground motion models predicting intensity measures on surface use a time-averaged shear wave velocity, VS30, as a key variable simulating site effect. The VS30 can be directly estimated from VS profiles if the profile depth (z) is greater than or equal to 30 m. However, some sites have VS profiles with z < 30 m. In this case VS30 can be predicted using extension models. This study proposes new coefficient sets for existing prediction equations using 297 Korea VS profiles. We have collected VS profiles from KMA and Geoinfo database. Fitting six existing methods to data, we suggest new coefficients for each method and evaluate their performance. It turns out that if z ≥ 15 m, the standard deviation (σ) of residual in log10 is 0.061, which indicates that the estimated VS30 is nearly accurate. If z < 15 m, the σ keeps increasing up to 0.1 for z = 5 m, so we caution the use of models at very low z. Nonetheless, we recommend investigating up to 30 m depth for VS30 calculation if possible.

키워드

참고문헌

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