Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Evaluation of the Effect of Waveform Micropiles on Reinforcement of Foundation Structures Through Field Load Tests

현장 재하시험을 통한 파형 마이크로파일의 기초보강 효과 분석

  • Baek, Sung-Ha (School of Civil and Environmental Engineering & Construction Engineering Research Institute, Hankyong National Univ.) ;
  • Han, Jin-Tae (Department of Geotechnical Engineering, Korea Institute of Civil Engr. and Building Tech.) ;
  • Kim, Seok-Jung (Planning and Coordination Department, Korea Institute of Civil Engr. and Building Tech.) ;
  • Kim, Joonyoung (Department of Artificial Intelligence, Hannam Univ.)
  • 백성하 (한경국립대학교 건설환경공학부) ;
  • 한진태 (한국건설기술연구원 지반연구본부) ;
  • 김석중 (한국건설기술연구원 경영기획실) ;
  • 김준영 (한남대학교 AI융합학과)
  • Received : 2023.03.07
  • Accepted : 2023.03.16
  • Published : 2023.03.31
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Abstract

In this study, we investigated the reinforcing effects of waveform micropiles in a stratigraphic setting comprising buried soil, weathered soil, and weathered rock. We conducted a series of field load tests and determined that waveform micropiles exhibited sufficient bearing capacity through frictional resistance in the soil layer and demonstrated favorable constructability in conditions with deep bedrock layers. Moreover, the vertical stiffness of waveform micropiles was approximately 2.2 times higher than that of conventional micropiles when subjected to the same design load. Pile group load tests comprising conventional and waveform micropiles showed that micropiles with higher stiffness carried a greater proportion of the load. Although there was no significant difference in the bearing capacity between conventional and waveform micropiles under the same design load, waveform micropiles with higher stiffness showed a load-carrying capacity 1.7 to 3.2 times greater than that of conventional micropiles. These findings suggest that waveform micropiles can be effectively used for foundation reinforcement and reduce the risk of foundation failure when increased loads due to modifications such as expansion remodeling are expected.

본 연구에서는 파형 마이크로파일의 기초보강 효과를 분석하기 위해서, 매립토-풍화토-풍화암의 지층구조를 보이는 지반에 마이크로파일을 설치한 뒤 현장 재하시험을 수행했다. 단일 마이크로파일 재하시험 결과, 파형 마이크로파일은 토사층에서 발현되는 주면마찰력만으로도 충분한 지지력을 가져 암반층의 심도가 깊은 지반 조건에서 유리한 시공성을 가질 수 있음을 확인하였다. 또한 동일한 설계하중이 적용되었음에도, 단일 마이크로파일 재하시험 시 설계 하중 범위 내에서 평가된 파형 마이크로파일의 연직강성이 일반 마이크로파일의 연직강성에 비해 약 2.2배 큰 것으로 나타났다. 일반 및 파형 마이크로파일로 구성된 무리말뚝 재하시험 결과, 강성이 큰 마이크로파일이 높은 하중을 분담하는 것으로 나타났다. 일반 및 파형 마이크로파일 모두 동일한 설계하중이 적용되어 지지력에는 큰 차이를 보이지 않았음에도, 강성이 큰 파형 마이크로파일이 작게는 1.7배에서 크게는 3.2배 큰 하중 분담율을 보였다. 파형 마이크로파일은 대부분 보강기초로 활용될 것으로 예상되는데, 증축 리모델링 등을 통해 추가적인 하중 작용 시 많은 하중을 분담함으로써 기존 기초의 지지력 파괴 가능성을 낮출 수 있을 것으로 기대된다.

Keywords

Acknowledgement

본 연구는 과학기술정보통신부 한국건설기술연구원 연구운영비지원(주요사업)사업으로 수행되었으며(과제번호 20230132-001, 건축물 내진성능 확보를 위한 삼축내진말뚝 개선 연구), 이에 깊은 감사를 드립니다.

References

  1. ASTM (1994), Standard test method for piles under static axial compressive load. ASTM standard D1143-81, In Annual book of ASTM standards.
  2. Bruce, D.A. and DiMillo, A.F. (1995), A Primer on Micropiles, Civil Engineering, 65(12), 51-54.
  3. Cappello, C., Zonta, D., Ait Laasri, H., Glisic, B., and Wang, M. (2018), Calibration of Elasto-magnetic Sensors on In-service Cable-stayed Bridges for Stress Monitoring, Sensors, Vol.18, No.2, p.466.
  4. FHWA (2005), Micropile Design and Construction: Reference Manual. FHWA-NHI-05-039, Federal Highway Administration, Vol.1, No.1, pp.7-28.
  5. Gomez, J., Cadden, A., and Bruce, D.A. (2003), Micropiles Founded in Rock: Development and Evolution of Bond Stresses under Repeated Loading, Proc. of the 12th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, Germany, pp.1911-1916.
  6. Han, J.T., Kim, S.R., Jang, Y.E., and Lee, S.H. (2013), Evaluation of Bearing Capacity of Waveform Micropile by Numerical Analyses, Journal of the Korea Academia-Industrial cooperation Society, Vol.14, No.11, pp.5906-5914. https://doi.org/10.5762/KAIS.2013.14.11.5906
  7. Jang, D.U. (2013), Seismic Reinforcement Techniques and Examples for Vertical/Horizontal Expansion of Apartment House Remodeling, Construction Engineering and Management, Vol.14, No.6, pp.34-39.
  8. Jang, Y.E. and Han, J.T. (2016), A Field Study on the Constructability and Performance Evaluation of Waveform Micropile, Journal of the Korean Geotechnical Society, Vol.32, No.10, pp.67-79. https://doi.org/10.7843/kgs.2016.32.10.67
  9. Jang, Y.E. and Han, J.T. (2018), Field Study on Axial Bearing Capacity and Load Transfer Characteristic of Waveform Micropile, Canadian Geotechnical Journal, Vol.55, No.5, pp.653-665. https://doi.org/10.1139/cgj-2017-0155
  10. Jang, Y.E. and Han, J.T. (2019), Analysis of the Shape Effect on the Axial Performance of a Waveform Micropile by Centrifuge Model Tests, Acta Geotechnica, 14, pp.505-518. https://doi.org/10.1007/s11440-018-0657-2
  11. Jang, Y.E., Kim, B., Wang, C., and Han, J.T. (2019), Prediction of Vertical Bearing Capacity of Waveform Micropile, Geotechnique Letters, Vol.9, No.3, pp.198-204.
  12. Jang, Y.E., Han, J.T., Kim, J.H., Park, H.J., and Kim, S.H. (2015), Evaluation of Axial Bearing Capacity of Waveform Micropile by Centrifuge Test, Journal of the Korean Geotechnical Society, Vol.31, No.8, pp.39-49. https://doi.org/10.7843/KGS.2015.31.8.39
  13. Juran, I., Benslimane, A., and Hanna, S. (2001), Engineering Analysis of Dynamic behavior of Micropile Systems, Transportation Research Record, 1772, pp.91-106.
  14. KGS (2009), Standard Guideline for the Design of Foundation Structures, Korean Geotechnical Society.
  15. KGS (2018), Commentary on Standard Guideline for the Design of Foundation Structures, Korean Geotechnical Society.
  16. Sadek, M. and Isam, S. (2004), Three-dimensional Finite Element Analysis of the Seismic behavior of Inclined Micropiles, Soil Dynamics and Earthquake Engineering, Vol.24, No.6, pp.473-485. https://doi.org/10.1016/j.soildyn.2004.02.002
  17. Skempton, A.W. and MacDonald, D.H. (1956), The Allowable Settlements of Buildings, Proceedings of the Institution of Civil Engineers, Vol.5, No.6, pp.727-768. https://doi.org/10.1680/ipeds.1956.12202
  18. Sumitro, S., Jarosevic, A., and Wang, M.L. (2002), Elasto-magnetic Sensor Utilization on Steel Cable Stress Measurement. In The First fib Congress, Concrete Structures in the 21th Century, Osaka, pp. 13-19.
  19. Tsukada, K., Miura, Y., Tsubokawa, Y., and Otani, G.L. (2006), Mechanism of Bearing Capacity of Spread Footings Reinforced with Micropiles, Soils and Foundations, Vol.46, No.3, pp.367-376. https://doi.org/10.3208/sandf.46.367
  20. You, G.L., Miura, K., and Ishito, M. (2003), Behavior of Micropile Foundation under Inclined Loads in Laboratory Tests, Journal of Lowland Technology International, Vol.5, No.2, pp.16-26.