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2013 Vol.29, Issue 12
Evaluation of Unit Side Resistance of Drilled Shafts by Revised SPT N Value

환산SPT N값을 이용한 현장타설말뚝의 단위주면마찰지지력 산정

Min-Seung Yoon1*
,
Chea-Keon Lee2
,
Myung-Hak Kim3
윤 민승1*
,
이 채건2
,
김 명학3
1Graduate Student, Dept. of Civil Engrg., Inje Univ.
2Section Chief, Dept. of Road Division, Gyeongsangnamdo
3Prof., Dept. of Civil Engrg., CTRC, Inje Univ.
1인제대학교, 토목공학과 박사과정
2경남도청, 도로과 도로과장
3인제대학교, 토목공학과 정교수
*교신저자. *Corresponding Author. 
31 December 2013. pp. 5-10
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Abstract

Bearing capacity of a drilled shaft can be separated into side resistance and base resistance. But in domestic design procedure side resistance is usually underestimated compared with base resistance. Results of bi-directional test showed that measured side resistances in each different layers are larger than those evaluated from several suggested methods. In this study, measured side resistances in each different layer of drilled shafts installed in domestic sites are analyzed and compared with evaluated side resistances from the method using revised SPT N value. For weathered rock and soft rock layer, from which rock core can hardly be obtained, we suggested new evaluated methods using revised SPT N value instead of the method using uniaxial compressive strength of rock. Resuts showed that the ranges of side resistance of cohesive and non-cohesive layer are and respectively. Range of side resistance in weathered rock is and that in soft rock .

Keywords
Unit side resistance
SPT N value
Uniaxial compression strength
Pile load test

말뚝의 지지력은 주면마찰력과 선단지지력으로 구분할 수 있고 설계지지력을 산정 시에는 말뚝의 지지형식에 따라 두 지지력을 모두 고려하거나 둘 중의 하나만을 고려하기도 한다. 본 연구에서는 국내 현장타설말뚝의 양방향재하시험을 결과를 분석하여 각 지층별로 측정된 단위주면마찰지지력 값을 국내외의 제안식으로 산정된 값과 비교분석하였다. 토사층의 경우 SPT N 값을 이용하는 제안식 값들이 재하시험을 통하여 실측된 단위주면마찰력에 비해 작아 과소평가되고 있음을 알 수 있었고, 암반층의 경우 국내외 제안식들이 암반의 일축압축강도를 기반으로 되어있어 코아시료 채취가 어려운 국내 풍화암이나 연암층에는 적용이 곤란하여 환산된 SPT N값을 이용한 산정식을 제안하였다. 그 결과 점성토의 단위주면마찰지지력은 , 사질토의 단위주면마찰지지력은 의 상한값을 제안할 수 있었다. 암반층에서는 수정 SPT N값에 따라 단위주면마찰력을 제안하였는데 풍화암층은 , 연암층은 으로 나타났다.

References
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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 : 29
  • No :12
  • Pages :5-10
  • Received Date : 2013-01-17
  • Revised Date : 2013-05-20
  • Accepted Date : 2013-12-16
  • DOI :https://doi.org/10.7843/kgs.2013.29.12.5
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