KSCE Journal of Civil and Environmental Engineering Research (대한토목학회논문집)

Korean Society of Civil Engeneers (대한토목학회)
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Reinforcing Effect of Buildings Considering Load Distribution Characteristics of a Pre-compressed Micropile

선압축 보강마이크로파일의 하중분담 특성을 고려한 건물 보강효과에 대한 연구

  • 이광훈 (수원대학교 건설환경공학과) ;
  • 박용찬 ((주)비티엠이엔씨 기술연구소) ;
  • 문성진 ((주)이도가컨설턴트 기술연구소) ;
  • 유광호 (수원대학교 건설환경공학과)
  • Received : 2021.11.24
  • Accepted : 2022.06.10
  • Published : 2022.12.01
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Abstract

Micropiles can be used to support additional load in extended building structures. However, their use brings about a risk of exceeding the bearing capacity of existing piles. In this study, pre-compression was applied to distribute the load of an existing building to micropiles, and an indoor loading test was performed to confirm the structural applicability of a wedge-type anchorage device designed to improve its capacity. According to the test results, the maximum strain of the anchorage device was 0.63 times that of the yield strain, and the amount of slip generated at the time of anchorage was 0.11 mm, satisfying structural standards. In addition, using MIDAS GTS, a geotechnical finite element analysis software, the effect of the size of the pre-compression, the thickness of the soil layer, and the ground conditions around the tip on the reaction force of the existing piles and micropiles were analyzed. From the numerical analysis, as the size of the pre-compression load increased, the reaction force of the existing pile decreased, resulting in a reduction rate of up to 36 %. In addition, as the soil layer increased by 5 m, the reduction rate decreased by 4 %, and when the ground condition at the tip of the micropile was weathered rock, the reduction rate increased by 14 % compared with that of weathered soil.

건물이나 구조물 증축 시 사용되는 마이크로파일은 추가하중의 일부만을 지지하여 기존 말뚝의 경우 허용지지력을 초과하는 문제가 발생할 수 있다. 본 논문에서는 건물의 하중을 마이크로파일에 분배하고자 선압축 공법을 적용하였고, 정착성능을 개선한 웨지형 정착장치의 적용성을 확인하고자 실내재하시험을 수행하였다. 시험결과, 정착장치의 최대변형률은 항복변형률의 0.63배였고, 웨지와 콘크리트 사이 슬립발생량은 0.11 mm로 구조적인 기준을 만족하였다. 또한, 지반범용 해석프로그램인 MIDAS GTS를 활용하여 선행 압축하중, 토사층 두께, 선단 지반조건이 기존 말뚝과 마이크로파일의 반력에 미치는 영향을 분석하였다. 해석결과, 선압축 하중의 크기가 증가할수록 기존말뚝의 반력이 감소하여 최대 36 %의 저감효과를 보였다. 토사층 두께가 5 m 증가됨에 따라 반력저감률은 4 % 감소하였고, 마이크로파일의 선단이 풍화암에 놓일 경우 풍화토와 비교하여 반력저감율이 14 % 증가하였다.

Keywords

Acknowledgement

본 연구는 '리모델링시 하중배분 기초보강용 프리컴프레션 마이크로파일 제품의 개발(S2973921)' 과제의 일환으로 2020년도 중소벤처기업부 구매조건부 신제품 개발사업의 지원으로 이루어졌습니다. 이에 감사드립니다. 본 논문은 2021 CONVENTION 논문을 수정·보완하여 작성되었습니다.

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