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2017 Vol.33, Issue 2 Preview Page
Evaluation of Permanent Lateral Displacement of a Cyclic Laterally Loaded Pile in Sandy Soil

모래지반에서 횡방향 반복하중을 받는 말뚝의 영구수평변위 평가

Sung-Ha Baek1
,
Joon-Young Kim2
,
Seung-Hwan Lee3
,
Choong-Ki Chung4*
백 성하1
,
김 준영2
,
이 승환3
,
정 충기4*
1Ph.D. Student, Dept. of Civil & Environmental Engrg., Seoul National Univ.
2Post Doc. Researcher, Eng. Research Institute, Seoul National Univ.
3Ph.D. Student, Dept. of Civil & Environmental Engrg., Seoul National Univ.
4Prof., Dept. of Civil & Environmental Engrg., Seoul National Univ.
1서울대학교 건설환경공학부 박사과정
2서울대학교 공학연구소 선임연구원
3서울대학교 건설환경공학부 박사과정
4서울대학교 건설환경공학부 교수
*교신저자. *Corresponding Author. 
28 February 2017. pp. 17-26
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Abstract

Pile foundations that support offshore structures or transmission towers are dominantly subjected to cyclic lateral loads due to wind and waves, causing permanent displacement which can severely affect stability of the structures. In this study, a series of cyclic lateral load tests were conducted on a pre-installed aluminum flexible pile in sandy soil with three different relative densities (40%, 70% and 90%) in order to evaluate the permanent displacement of a cyclic laterally loaded pile. Test results showed that the cyclic lateral loads accumulated the irreversible lateral displacement, so-called permanent displacement. As the number of cyclic lateral load increased, accumulated permanent displacement increased, but the permanent displacement due to one loading cycle gradually decreased. In addition, the permanent displacement of a pile increased with decrement of relative density and decreased by soil saturation. From the test results, the normalized permanent displacement defined as the cumulative permanent displacement to the initial permanent displacement ratio was investigated, and empirical equations for predicting the normalized permanent displacement was developed in terms of relative density of the soil and the number of cyclic lateral load.

Keywords
Pile foundation
Model pile test
Cyclic lateral load
Permanent lateral displacement
Relative density

해상구조물, 송전탑 등을 지지하는 말뚝기초는 바람, 조류, 파랑 등의 영향으로 횡방향 반복하중을 지배적으로 받으며, 이는 말뚝 주변 지반에 영구수평변위를 발생시켜 구조물의 안정성 및 기능성을 저해한다. 본 연구에서는 횡방향 반복하중에 의해 발생하는 말뚝의 영구수평변위를 평가하기 위하여, 서로 다른 세 가지 상대밀도(40%, 70%, 90%)로 조성된 건조 및 포화 모래지반에서 모형말뚝시험을 수행하였다. 모형시험 결과, 모든 시험조건에서 말뚝에 재하 된 횡방향 반복하중은 말뚝 주변 지반에 영구수평변위를 발생시켰다. 누적된 영구수평변위의 크기는 말뚝에 재하되는 횡방향 반복하중의 크기 및 재하횟수가 증가함에 따라 증가하였지만, 1회 재하로 인하여 발생되는 영구수평변위의 증가량은 점차 감소하였다. 또한, 말뚝에 발생하는 영구수평변위는 지반의 상대밀도가 클수록 작게 발생하고, 지반이 포화되면 크게 발생되는 것으로 평가되었다. 추가적으로, 누적 영구수평변위를 최초 재하 시 발생한 영구수평변위로 정규화한 영구수평변위를 평가하였으며, 이를 모래지반의 상대밀도, 횡방향 반복하중의 재하횟수에 관한 식으로 나타내었다.

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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 : 33
  • No :2
  • Pages :17-26
  • Received Date : 2016-11-16
  • Revised Date : 2017-01-10
  • Accepted Date : 2017-01-16
  • DOI :https://doi.org/10.7843/kgs.2017.33.2.17
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