Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Numerical Study on the Stress-distribution Ratio of Grouting Pile for Reinforced Ground

지반보강용 그라우팅 말뚝의 응력분담비에 대한 수치해석적 연구

  • 이경주 (인하대학교 토목공학과, 에스큐엔지니어링) ;
  • 이준규 (서울시립대학교 토목공학과 ) ;
  • 張維維 (인하대학교 토목공학과) ;
  • 송기일 (인하대학교 토목공학과 )
  • Received : 2022.12.12
  • Accepted : 2023.02.17
  • Published : 2023.02.28
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Abstract

Underground structures, such as compacted sand piles applied as soft ground countermeasures, are analyzed for settlement and stability by the composite ground design method. The basic principle of the composite ground design method is the arching effect. The reinforcing effect of the pile is evaluated as the stress-distribution ratio. When applying grouting piles with elastic properties using the ground reinforcement method, the existing stress-distribution ratio was only considered when the pile was installed. This study shows that the method of applying the stress-distribution ratio applied in previous studies should be changed when the ground reinforcement pile is installed at an arbitrary location in the ground without raising it to the ground surface. When high strength jet routing is applied, the stress-distribution ratio (n) to the in-situ ground generally ranges from 30 to 50. However, if the pile is located far from the surface and the depth goes down to the boundary depth of the stress sphere, the stress-distribution effect rapidly decreases, and the stress-distribution ratio converges to 1.5.

연약지반 대책공법으로 적용되는 다짐모래말뚝과 같은 지중구조물은 주로 복합지반 설계법에 의해 침하 및 안정성을 분석한다. 복합지반 설계법의 기본원리는 아칭효과이며 말뚝의 보강효과는 응력분담비로 평가한다. 탄성적 특성을 갖는 그라우팅 말뚝을 지반보강공법으로 적용할 때 기존의 응력분담비 평가는 말뚝이 지표까지 설치되어 상재하중이 말뚝과 원지반에 같이 직접 재하되는 경우만을 고려해 왔다. 본 연구에서는 지반보강 말뚝의 설치를 지표까지 올리지 않고 지중 어느 위치에서 마감할 때에는 지금까지의 연구들에 의해 적용된 응력분담비 적용 방법이 달라져야 한다는 것을 보여주었다. 고강도 Jet grouting이 적용되었을 때 원지반에 대한 그라우팅 말뚝의 응력분담비(n)는 통상 30~50 범위의 값을 적용한다. 그러나 이는 지표까지 말뚝이 놓이는 경우이고 말뚝 상단의 위치가 지표로부터 멀리 깊게 위치될 경우 응력분담 효과가 급격히 저감되며 응력구(stress bulb) 경계가 되는 깊이부터는 정량적 값 1.5에 수렴했다.

Keywords

Acknowledgement

본 논문은 행정안전부 "산지(경사지) 태양광 발전시설의 전주기 스마트 안전관리 기술 개발(20018265)"의 지원을 받아 작성되었으며 이에 감사드립니다.

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