All Issue

2021 Vol.37, Issue 2 Preview Page

Research Article

3-D Numerical Analysis for the Verification of Bearing Mechanism and Bearing Capacity Enhancement Effect on the Base Expansion Micropile

선단 확장형 마이크로파일의 3차원 수치해석을 통한 지지 메커니즘 및 지지력 증대효과 검증

Seokhyung Lee1
,
Jin-Tae Han2
,
Hyun-Sik Jin3
,
Seok-Jung Kim4†
이 석형1
,
한 진태2
,
진 현식3
,
김 석중4†
1Member, Postdoctoral Researcher, Dept. of Infrastructure Safety Research, Korea Inst. of Civil Eng. and Building Tech.
2Member, Research Fellow, Dept. of Infrastructure Safety Research, Korea Inst. of Civil Eng. and Building Tech.
3Member, CEO, Hydraulic and Geotechnical Consultants
4Member, Senior Researcher, Dept. of Infrastructure Safety Research, Korea Inst. of Civil Eng. and Building Tech.
1정회원, 한국건설기술연구원 인프라안전연구본부 박사후연구원
2정회원, 한국건설기술연구원 인프라안전연구본부 연구위원
3정회원, ㈜에이치앤지컨설턴트 대표이사
4정회원, 한국건설기술연구원 인프라안전연구본부 수석연구원
*seokjungkim@kict.re.kr
28 February 2021. pp. 19-31
PDF XML Citation
Abstract

Micropiles are cast-in-place piles with small diameters. The advantage of micropile is low construction expense and simple procedures, so it is widely applied to existing buildings and structures for the reinforcement of foundation and seismic performances. The base expansion structure has been developed following the original mechanism of horizontal expansion steps under compressive loading. This kind of structure can be installed at the pile end to improve the bearing capacity by tip area enlargement and horizontal force increment to the pile surface area. However, ‘Micropile with base expansion structure’ cannot be put into practical use, because detailed verification for the developed technique has not been conducted so far. In this research, 3-D numerical analysis was conducted to figure out the bearing mechanism of base expansion micropile and to verify the bearing capacity improvement compared to the general micropiles. 3-D modelling of micropile with base expansion structure was carried out and input parameter was determined. Bearing mechanism induced by base expansion structure was analyzed by lab-scale modelling, and bearing capacity improvement was verified by field-scale analysis.

Keywords
Base expansion
Foundation reinforcement
Micropile
Numerical analysis
Seismic design

마이크로파일은 소구경 현장타설말뚝으로 간단한 시공법과 비교적 저렴한 공사비용으로 각종 건축물 및 구조물 기초보강 및 내진보강 등에 활용되고 있다. 말뚝 선단에 단순한 메커니즘의 고정 지압 구조체를 장착하여, 상부하중 작용 시 지압구가 압축·팽창하면서 선단 면적의 확대와 주면으로의 쐐기수평력을 발휘하여 지지력을 증대시키는 “선단 확장형 마이크로파일”이 개발되었으나, 개발된 공법에 대한 정확한 검증이 부족하여 실제 현장에서 활용되지 못하고 있는 실정이다. 이에 본 연구에서는, 선단 확장형 마이크로파일의 지지 메커니즘과 일반 마이크로파일 대비 지지력 증대효과를 검증하고자 3차원 수치해석을 수행하였다. 선단 확장형 마이크로파일을 모델링하고 수치해석을 위한 입력 물성치를 산정하였으며, Lab-scale 수치해석을 통하여 고정 지압 구조체가 압축·팽창되면서 발현되는 수평력에 의한 지지 메커니즘을 확인하였다. 이와 더불어 Field-scale 수치해석을 통해 일반 마이크로파일과의 지지력을 비교·검증한 결과, 압축 및 인발지지력이 각각 20.0%와 38.9% 증대되는 것을 확인하였다.

References
1
Babu, G.L.S. and Murthy, B.S. and Murthy, D.S.N. and Nataraj, M.S. (2004), "Bearing Capacity Improvement Using Micropiles: A Case Study", Geotechnical Special Publications, No.124, pp.0895-0563. 10.1061/40713(2004)14
2
Construction Information Studies Institute (2011), Status and Analysis of Domestic Pile Market, pp.4-22.
3
Fadeev, A.B., Inozemtsev, V.K., and Lukin, V.A. (2003), "Effective Micropiles for the Strengthening of Foundations", Soil Mechanics and Foundation Engineering, Vol.40, No.2, pp.69-71. 10.1023/A:1024492203444
4
Farouk, A. (2009), "Behavior of Micropiles under Vertical Tension and Compression Loads", Proceedings of the international conference on soil mechanics and geotechnical engineering, pp.1243-1246.
5
FHWA (2005), "Micropile Design and Construction", Publication No. FHWA NHI-05-039, U.S Department of Transportation, Washington, D.C.
6
Hill, R. (1950), "The Mathematical Theory of Plasticity", Oxford University Press, London, U.K.
7
Hwang, G.C., Ahn, U.J., Lee, J.S., and Ha, I.S. (2018), "A Study on the Bearing Characteristics of No-grouted and End-compressed Micropile Adopting Wedge Horizontal Force", Journal of The Korean Geotechnical Society (KGS), Vol.34, No.3, pp.67-75.
8
Hwang, T.H., Mun, K.R., Shin, Y.S., and Kwon, O.Y. (2012), "Installation of Micro-piles Appropriate to Soil Conditions", Journal of The Koran Geotechnical Society (KGS), Vol.28, No.4, pp.55-65. 10.7843/kgs.2012.28.4.55
9
Murthy, B.S., Babu, G.L.S., and Srinivas, A. (2002), "Analysis of Bearing Capacity Improvement Using Micropiles", Ground Improvement, Vol.6, No.33, pp.121-128. 10.1680/grim.2002.6.3.121
10
Sabatini, P.J. and Burak T. (2005), "Micropile Design and Construction Reference Manual", FHWA-NHI-05-039, U.S Department of Transportation, Washington, D.C.
11
Smith, I.M. and Griffiths, D.V. (1982), Programming the Finite Element Method, John Wiley & Sons, Chisester, U.K., 2nd edition.
12
Vermeer, P.A. and Borst, R. (1984), Non-associated plasticity for soils, Concrete and rock, Heron, 29(3).
Information
  • Publisher :The Korean Geotechnical Society
  • Publisher(Ko) :한국지반공학회
  • Journal Title :Journal of the Korean Geotechnical Society
  • Journal Title(Ko) :한국지반공학회 논문집
  • Volume : 37
  • No :2
  • Pages :19-31
  • Received Date : 2021-02-09
  • Revised Date : 2021-02-19
  • Accepted Date : 2021-02-20
  • DOI :https://doi.org/10.7843/kgs.2021.37.2.19
Journal Informaiton Journal of the Korean Geotechnical Society Journal of the Korean Geotechnical Society
Archives
: Vol.23~28 (2007~2012)
  • NRF
  • KOFST
  • KISTI Current Status
  • KISTI Cited-by
  • crosscheck
  • orcid
  • open access
  • ccl
Journal Informaiton Journal Informaiton - close