Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Evaluation of Bearing Capacity Enhancement Effect of Base Expansion Micropile Based on a Field Load Test

현장재하시험을 통한 선단확장형 마이크로파일의 지지력 증대효과 분석

  • Kim, Seok-Jung (Planning and Coordination Department, Korea Institute of Civil Engineering and Building Technology) ;
  • Lee, Seokhyung (Department of Structure & Site Evaluation, Korea Institute of Nuclear Safety) ;
  • Han, Jin-Tae (Department of Geotechnical Engineering, Korea Institute of Civil Engineering and Building Technology) ;
  • Hwang, Gyu-Cheol (Jaesung Construction Co. Ltd.) ;
  • Lee, Jeong-Seob (Design Department, Sejin E&C Co. Ltd.) ;
  • Yoo, Mintaek (Dept. of Civil and Enviornmental Eng., Gachon Univ.)
  • 김석중 (한국건설기술연구원 경영기획실 ) ;
  • 이석형 (한국원자력안전기술원 구조부지평가실 ) ;
  • 한진태 (한국건설기술연구원 지반연구본부) ;
  • 황규철 (재성건설) ;
  • 이정섭 ((주)세진이엔시 설계부 ) ;
  • 유민택 (가천대학교 토목환경공학과 )
  • Received : 2023.03.14
  • Accepted : 2023.03.23
  • Published : 2023.04.30
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Abstract

A base expansion micropile was developed to improve the bearing capacity of the micropile, which bears a simple device installed at the pile base. Under an axial load, this base expansion structure radially expands at the pile tip and attaches itself around ground, compressing the boring wall in the construction stage. In this study, conventional and base expansion micropiles were constructed in the weathered rock where micropiles are commonly installed. Further, field load tests were conducted to verify the bearing capacity enhancement effect. From the load test results, it was revealed that the shaft resistance of base expansion micropiles was about 12% higher than that of conventional micropiles. The load transfer analysis results also showed that compared to conventional micropiles, the unit skin friction and unit end bearing of base expansion micropiles were 15.4% and 315.1% higher, respectively, in the bearing zone of the micropile.

선단확장형 마이크로파일은 시공시 강봉 선단에 확장 구조체를 설치하여, 강봉이 지중에 설치될 때 자중 등 압축하중이 작용하여 선단확장구가 팽창, 천공홀 주변 지반을 압착함으로써 선단부에서의 추가적인 마찰력 및 선단 지지력을 확보함으로써 지지력 증대효과를 유발하는 공법이다. 본 연구에서는 마이크로파일이 일반적으로 시공되는 풍화암 근입지반에 마이크로파일을 시공하고 재하시험을 수행하여 선단확장형 마이크로파일의 지지력 증대효과를 분석하였다. 정재하 시험 결과, 선단확장형 마이크로파일의 지지성능은 일반마이크로파일의 주면지지력 대비 약 12% 크게 발현됨을 확인하였다. 추가로, 하중전이분석을 통해 단위 주면지지력과 선단지지력을 비교한 결과, 최대 단위주면지지력은 일반 마이크로파일 대비 약 15.4%, 선단지지력의 경우, 약 315.1% 크게 나타나, 선단 지압구의 효과에 따라 지지력 증대효과가 발생함을 확인하였다.

Keywords

Acknowledgement

본 연구는 과학기술정보통신부 한국건설기술연구원 연구운영비지원(주요사업)사업으로 수행되었습니다(과제번호 20230132-001, 건축물 내진성능 확보를 위한 삼축내진말뚝 개선 연구).

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