Characteristics of Undrained Shear Strength and Development of Modified SPT on Very Soft Ground in Korea

국내 초연약지반의 비배수전단강도 특성 및 개량표준관입시험기 개발

  • Jung, Hyuksang ;
  • Cho, Changkoo ;
  • Chun, Byungsik
  • 정혁상 (한양대학교 대학원 건설환경공학과) ;
  • 조창구 (한양대학교 대학원 건설환경공학과) ;
  • 천병식 (한양대학교 공과대학 건설환경공학과)
  • Received : 2009.08.10
  • Accepted : 2009.09.17
  • Published : 2009.10.01


In this study, SPT, FV, and CPT tests were performed at five very soft grounds in southern coast of Korea to characterize the $S_u$ of very soft ground. In addition, a new modified SPT that is applicable to very soft ground was developed. Tests results showed that in very soft ground (N<2), the $S_u$ was lower than 12.5 kPa using the empirical N-Su correlation, and lower than 50 kPa and 65 kPa using vane shear test and CPT, respectively. It was shown that the results of in-situ tests were higher than those estimated from the N-Su correlation, and it was also demonstrated that the range of estimated $S_u$ was quite wide. New correlations that relate the modified SPT $N_m$ with Su from FV and CPT were developed, which are $S_u=1.76N_m-10.47$ and $S_u=1.82N_m-9.71$, respectively.


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