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2016 Vol.32, Issue 9 Preview Page
Partial Drainage Characteristics of Clayey Silt with Low Plasticity from the West Coast

서해안 저소성 점토질 실트 지반의 부분배수 특성

Seok-Jo Kim1
김 석조1
Sang-Duk Lee2
이 상덕2
Ju-Hyun Kim3*
김 주현3*
1Member, Ph. D. Student, Dept. of Civil and Transportation Eng., Ajou Univ.
2Member, Prof., Dept. of Civil and Transportation Eng., Ajou Univ.
3Member, Affiliated Prof., Dept. of Civil Eng., Dongshin Univ.
1정회원, 아주대학교 건설시스템공학과 박사과정
2정회원, 아주대학교 건설시스템공학과 교수
3정회원, 동신대학교 토목공학과 겸임교수
*교신저자. *Corresponding Author. 
30 September 2016. pp. 17-27
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Abstract

Parial drainage characteristics of clayey silt with low plasticity from the west coast (Incheon and Hwaseong) was analyzed using CPTU based existing correlation equations and compulsory replacement method. Generally, the estimated OCRs = κ･() using Powell and Quartman(1988) were higher than those obtained by the oeodometer tests. These trends were noticeable for the layers containing a lot of silty and sand soils. The assessment of partial drainage conditions was performed through Schnaid et al. (2004)’s equation; it is based on plotting the normalized cone resistance, Qt versus the pore pressure parameter, Bq in combination with the strength incremental ratio, to the CPTU data. It is evident that more than half of the data fall in the range where Bq < 0.3, corresponding to the domain in which the partial drainage prevails when testing normally consolidated soils at a standard rate of penetration (2 cm/s). To estimate the replacement depth of clayey silt with low plasticity, back analysis was carried out to evaluate the internal friction angle based on where the design depths are equal to the checked depths using bearing capacity equation. The internal friction angels obtained from the back analysis tended to increase as the plasticity index decreases, which is ranged approximately from φ'=2° to φ'=7°.

Keywords
Clayey silt with low plasticity
Partial drainage characteristics
Pore pressure parameter

서해안의 인천 및 화성지역에 분포하는 모래 및 실트 함유량이 많은 저소성 지반에 대해 피에조콘관입시험(CPTU) 데이터 및 강제치환 공법을 이용하여 부분배수 특성을 분석하였다. Powell과 Quarterman(1988)에 의한 과압밀비 OCR=κ() 경험식은 모래함유량이 많은 서해안 저소성 실트 지반에서는 상대적으로 투수성이 커서 표준관입속도(2cm/s)하에서 콘관입저항력(qt)이 크게 평가되어 과압밀비가 크게 산정되는 경향을 나타냈다. Schnaid et al. (2004)는 간극수압계수(Bq)-강도증가율()-정규화된 콘저항(Qt =)을 함께 도시하여, 부분배수 유무를 판단하도록 제시하였는데, 인천 및 화성 지역의 CPTU 데이터의 50% 이상이 부분배수 상태를 나타내는 Bq < 0.3에 분포하였다. 또한, 강제치환 시공과정 중 부분배수 현상으로 인해 원지반의 강도증가 현상이 발생되어 설계 예상 치환깊이보다 훨씬 작은 실측값이 얻어진다는 관점에서 실측 치환깊이와 동일한 값이 얻어지도록 원지반의 지지력에 대한 역해석을 수행하였다. 그 결과, 소성지수가 감소할수록 내부마찰각이 커지는 경향을 나타내며, 내부마찰각(φ')이 2∼7°의 범위에서 분포하는 것으로 분석되었다.

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Information
  • Publisher :The Korean Geotechnical Society
  • Publisher(Ko) :한국지반공학회
  • Journal Title :Journal of the Korean Geotechnical Society
  • Journal Title(Ko) :한국지반공학회 논문집
  • Volume : 32
  • No :9
  • Pages :17-27
  • Received Date : 2016-05-20
  • Revised Date : 2016-07-22
  • Accepted Date : 2016-09-01
  • DOI :https://doi.org/10.7843/kgs.2016.32.9.17
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