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Research Article

Assessment of p-y Behaviors of a Cyclic Laterally Loaded Pile in Saturated Dense Silty Sand

조밀한 포화 실트질 모래지반에서 횡방향 반복하중을 받는 말뚝의 p-y 거동 평가

Sung-Ha Baek1
,
Changho Choi2
,
Jinwoo Cho3
,
Choong-Ki Chung4*
백 성하1
,
최 창호2
,
조 진우3
,
정 충기4*
1Member, Senior Researcher, Korea Institute of Civil Engr. and Building Tech.
2Member, Research Fellow, Korea Institute of Civil Engr. and Building Tech.
3Member, Senior Researcher, Korea Institute of Civil Engr. and Building Tech.
4Member, Prof., Dept. of Civil & Environmental Engrg., Seoul National Univ.
1정회원, 한국건설기술연구원 미래융합연구본부 수석연구원
2정회원, 한국건설기술연구원 미래융합연구본부 연구위원
3정회원, 한국건설기술연구원 미래융합연구본부 수석연구원
4정회원, 서울대학교 건설환경공학부 교수
* Corresponding Author
30 November 2019. pp. 97-110
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Abstract

해상풍력 구조물을 지지하는 말뚝기초는 바람, 파랑, 조류 등에 의한 횡방향 반복하중을 지배적으로 받는다. 해상풍력 구조물의 안정적인 성능확보를 위해서 횡방향 반복하중을 받는 말뚝기초의 지지거동을 적절히 평가해 설계에 적용할 필요가 있으며, 말뚝 및 지반을 각각 탄성빔과 비선형 스프링으로 가정하는 p-y 곡선방법이 가장 널리 활용되고 있다. 본 연구에서는 조밀한 포화 실트질 모래지반에 설치되어 횡방향 반복하중을 받는 말뚝기초의 p-y 거동을 평가하기 위해서, 1g 모형말뚝시험을 수행했다. 모형시험 결과, 말뚝에 횡방향 반복하중 재하 시 p-y 곡선의 강성(초기기울기 및 최대지반반력)이 점차 감소했다. p-y 곡선의 강성감소는 반복하중의 크기가 크고 지표면에 가까운 위치에서 더 명확하게 나타났는데, 상기조건에서 말뚝 주변지반의 교란효과가 크게 발생해 지반의 지지능력이 더욱 크게 감소했기 때문이다. 모형시험 결과를 활용해 조밀한 포화 실트질 모래지반에 설치되어 횡방향 반복하중을 받는 말뚝기초의 p-y 곡선을 제안했다. 등가정적해석을 통해 예측된 말뚝거동을 모형시험결과와 비교한 결과, 제안된 식을 통해 비교적 조밀하고 포화된 실트질 모래지반에서 반복하중을 받는 말뚝의 횡방향 지지거동을 적절히 평가할 수 있음을 확인했다.

Piles that support offshore wind turbine structures are dominantly subjected to cyclic lateral loads of wind, waves, and tidal forces. For a successful design, it is imperative to investigate the behavior of the cyclic laterally loaded piles; the p-y curve method, in which the pile and soil are characterized as an elastic beam and nonlinear springs, respectively, has been typically utilized. In this study, model pile tests were performed in a 1 g gravitational field so as to investigate the p-y behaviors of cyclic laterally loaded piles installed in saturated dense silty sand. Test results showed that cyclic lateral loads gradually reduced the overall stiffness of the p-y curves (initial stiffness and ultimate soil reaction). This is because the cyclic lateral loads disturbed the surrounding soil, which led to the decrement of the soil resistance. The decrement effects of the overall stiffness of the p-y curves became more apparent as the magnitude of cyclic lateral load increased and approached the soil surface. From the test results, the cyclic p-y curve was developed using a p-y backbone curve method. Pseudo-static analysis was also performed with the developed cyclic p-y curve, confirming that it was able to properly predict the behaviors of cyclic laterally loaded pile installed in saturated dense silty sand.

Keywords
Cyclic lateral load
Dense silty sand
Model pile test
Offshore pile foundation
p-y curve

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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 : 35
  • No :11
  • Pages :97-110
  • Received Date : 2019-10-30
  • Revised Date : 2019-11-12
  • Accepted Date : 2019-11-13
  • DOI :https://doi.org/10.7843/kgs.2019.35.11.97
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