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Evaluation on Partially Drained Strength of Silty Soil With Low Plasticity Using CPTU Data

CPTU 데이터를 이용한 저소성 실트 지반의 부분배수 강도 평가

Ju-Hyun Kim1*
김 주현1*
1Member, Adjunct Professor, Department of Civil Engineering, Dongshin University
*교신저자. *Corresponding Author. 
30 June 2017. pp. 55-66
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Abstract

The standard piezocone penetration rate of 2 cm/s is proposed in specifications regardless of soil type. However, conditions of standard Piezo Cone Penetration (CPTU) Testings in silty soils with low plasticity vary from undrained to partially drained or fully drained penetration conditions. The partially drained shear strengths of Incheon, Hwaseong and Gunsan silty soils were estimated from the analysis results of the distributions of CPTU-based shear strengths. The CPTU-based shear strengths were compared between the undrained shear strength line and the fully drained shear strength line, which were determined from approximately φ'=3° and φ'=15°, respectively. The internal friction angles obtained from the back analysis and UU-tests tended to increase with decreasing plasticity index, which range approximately from φ'=2° to φ'=14°. The results matchs well with CPTU-based estimation results.

Keywords
Partially drained shear strength
Silty soil
Low plasticity
CPTU data
Cone factor

본 연구에서는 지반 특성에 관계없이 일률적으로 적용되는 피에조콘 관입속도 2cm/s 조건 하에서, 저소성 실트 지반의 경우 부분배수 내지는 완전 배수 현상이 발생된다는 관점에서 저소성 실트 지반의 비배수전단강도선과 완전배수 전단강도선 사이 에서의 피에조콘계수(Nkt)에 의한 전단강도 분포 경향을 기준으로 부분배수 전단강도를 평가하였다. 그 결과, 인천, 화성 및 군산 저소성 실트 지반의 부분배수 내부마찰각(φ′)은 3∼15°에서 분포하는 것으로 분석되었다. 한편, 강제치환 역해석 결과 및 비압밀비배수 삼축시험으로부터 얻어진 내부마찰각(φ′)은 소성지수 감소에 따라 2～14°의 범위에서 분포되어, CPTU 데이 터에 의한 부분배수 내부마찰각(φ′)과 유사한 경향을 나타내어 이에 대한 적용성을 확인할 수 있었다.

References
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Information
  • Publisher :Korean Geosythetics Society
  • Publisher(Ko) :한국지반신소재학회
  • Journal Title :Journal of the Korean Geosynthetics Society
  • Journal Title(Ko) :한국지반신소재학회 논문집
  • Volume : 16
  • No :2
  • Pages :55-66
  • Received Date : 2017-05-21
  • Revised Date : 2017-06-10
  • Accepted Date : 2017-06-13
  • DOI :https://doi.org/10.12814/jkgss.2017.16.2.055
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