Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
권호 표지

A Proposition of Site Coefficients and Site Classification System for Design Ground Motions at Inland of the Korean Peninsula

국내 내륙의 설계 지반 운동 결정을 위한 지반 증폭 계수 및 지반 분류 체계 제안

  • Sun Chang-Guk (Highway & Transp. Tech. Inst., Korea Highway Corp.,) ;
  • Chung Choong-Ki (School of Civil, Urban & Geosystem Eng., Seoul National Univ.) ;
  • Kim Dong-Soo (Dept. of Civil & Evbironmental Eng., Korea Adanced Inst. Of Science & Tech.)
  • 선창국 (한국도로공사 도로교통기술원) ;
  • 정충기 (서울대학교 지구환경시스템공학부) ;
  • 김동수 (한국과학기술원 건설및환경공학과)
  • Published : 2005.08.01
Download PDF
⟨ Previous Next ⟩

Abstract

For the site characterization at two inland areas, Gyeongju and Hongsung, which represent geomorphic and geologic characteristics of inland region in Korea, in-situ seismic tests containing borehole drilling investigations and resonant column tests were peformed and site-specific seismic response analyses were conducted using equivalent linear as well as nonlinear scheme. The soil deposits in Korea were shallower and stiffer than those in western US, from which the site coefficients and site classification system in Korea were derived. Most sites were categorized as site classes C and D based on the mean shear wave velocity $(V_s)$ of the upper 30 m $(V_s30)$, ranging between 250 and 650 m/s. According to the acceleration response spectra determined from the site response analyses, the site coefficients specified in the current Korean seismic design guide underestimate the ground motion in the short-period band and overestimate the ground motion in mid-period band. These differences can be explained by the differences in the bedrock depth and the soil stiffness profile between Korea and western US. The site coefficients, $F_a$ for short-period and $F_v$ for mid-period, were re-evaluated and the site classification system, in which sites C and D were subdivided according to $V_s20,\;V_s15,\;and\;V_s10$ together with the existing $V_s30$ was introduced accounting for the local geologic conditions at inland region of the Korean peninsula. The proposed site classification system in this paper is still rudimentary and requires modification.

국내 내륙의 지형 및 지질 특성을 대표하는 두 지역인 경주와 홍성을 대상으로 전단파 속도$(V_s)$ 획득 목적의 현장 탄성파 시험을 포함한 다양한 지반 조사를 실시하여 지반 특성을 평가하고, 이를 토대로 등가 선형 및 비선형 기법의 부지 응답 해석을 수행하였다. 현행 국내 내진 설계의 근간인 미국 서부 지역과의 지반 특성 비교 결왔 국내 내륙 지역의 기반암 심도는 매우 얕고 강성은 다소 컸다. 지반 분류 기준인 심도 30m까지의 평균 전단파 속도$V_s30$는 대상 지역 내에서 $250\sim650m/s$의 좁은 범위의 분포를 보였고, 그에 따라 대부분의 부지가 C와 D 지반 조건으로 분류되었다. 부지 응답 해석 결과로부터 현행 국내 내진 설계를 위한 단주기 증폭 계수$(F_ㅁ)$는 지반 운동을 과소평가하고 중장주기 증폭계수$(F_v)$는 과대평가하고 있음을 확인하였다. 이에 따라 국내 내륙 지역에 대한 지반 증폭 계수를 재산정하고, 지역적 지반 특성을 고려하여 기존 지반 분류 C 및 D의 세부 분류와 지표면 부근 심도까지의 평균 $V_s$인 $V_s20,\;V_s15,$ 와 $V_s10$의 추가 분류 기준이 적용된 합리적 지반 분류 체계를 제안하였다. 제안된 지반 분류 체계는 현재로서는 예비적인 방안이므로 향후 보완 및 개선이 필요할 것으로 판단된다.

Keywords

References

  1. 건설교통부 (1999), 내진설계기준연구(II)
  2. ANSS Technical Integration Committee (2001), Technical Guideline for the Implementation of an Advanced National Seismic System, Advanced National Seismic System, http://www.anss.org/ticplan, Accessed in 14 April 2002
  3. Bardet, J. P. and Tobita, T. (2001), NERA: A Computer Program for Nonlinear Earthquake Site Response Analyses of Layered Soil Deposits, University of Southern California
  4. Borcherdt, R. D. (1994), 'Estimates of site-dependent response spectra for design (methodology and justification)', Earthquake Spectra, Vol.10, pp.617-653 https://doi.org/10.1193/1.1585791
  5. BSSC (2000), NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures, Part 1-Provisions, Building Seismic Safety Council, Washington D. C
  6. Dobry, R., Ramos, R., and Power, M. S. (1999), Site Factor and Site Categories in Seismic Codes, Technical Report MCEER-99-0010, Multidisciplinary Center for Earthquake Engineering Research
  7. ICBO (1997), 1997 Uniform Building Code, Volume 2 - Structural Engineering Design Provisions, International Conference of Building Officials
  8. Idriss, I. M., and Sun, J. I. (1992), User's Manual for SHAKE91: A Computer Program for Conducting Equivalent Linear Seismic Response Analyses of Horizontally Layered Soil Deposits, University of California, Davis
  9. Imai, T. and Tonouchi, K. (1982), 'Correlation of N-value with S-wave Velocity and Shear Modulus', Proceedings of the 2nd European Symposium on Penetration Testing, Amsterdam, pp.57-72
  10. Kim, D. S., Chung, C. K., Sun, C. G., and Bang, E. S. (2002), 'Site assessment and evaluation of spatial earthquake ground motion of Kyeongju', Soil Dynamics and Earthquake Engineering, Vol.22, pp.371-387 https://doi.org/10.1016/S0267-7261(02)00023-4
  11. Sun, C. G. (2004), Geotechnical Information System and Site Amplification Characteristics for Earthquake Ground Motions at Inland of the Korean Peninsula, Ph.D. Dissertation, Seoul National University