DOI QR코드

DOI QR Code

An Empirical Formula of Bearing Capacity on Prebored and Precast Steel Piles

강관 매입말뚝의 지지력 공식 제안

  • 박종전 (연세대학교 토목환경공학과) ;
  • 김도현 (매사추세츠공과대학교 토목환경공학과) ;
  • 정경자 (한국도로공사 도로교통연구원) ;
  • 정상섬 (연세대학교 토목환경공학과)
  • Received : 2021.02.08
  • Accepted : 2021.04.14
  • Published : 2021.06.30

Abstract

In this study, a modified empirical formula for estimating the bearing capacity of the steel pipe prebored and precast pile was proposed by performing 20 cases of real-scale field pile loading tests. The proposed formula will be based on expanded SPT N-value in order to consider the realistic condition of the surrounding soil. The formula is proposed based on a statistic approach of the data points from the field pile loading test, in order to ensure safe engineering practice while finding a reliable formula. The statistical analysis of the data points from the loading test indicated that the existing formula has been underestimated the bearing capacity of the prebored and precast pile. The proposed formula estimates 15% and 20% higher pile End bearing capacity (qt=230Pdriven(kN/m2)) and the shaft resistance (fmax=3.0NsE(kN/m2)) compared to the existing formula. The accuracy and the stability of the proposed formula was verified by comparing the estimated results with additional field test data. The verification process showed that the proposed formula was estimated to be more accurate than the existing formula.

본 연구에서는 풍화암에 근입된 강관 매입말뚝의 지지력 공식 제안을 위하여 정재하시험 20본과 확인지반조사를 수행하였다. 기존 공식의 표준관입저항치를 50으로 제한하는 문제를 극복하기 위해 지반 현장 상태를 고려할 수 있도록 확장된 표준관입저항치를 기반으로 새로운 지지력 공식을 제안하였다. 재하시험 데이터는 통계적 처리를 수행하였다. 이때, 통계적 처리를 수행하여 얻어진 지지력과 기존공식을 이용한 지지력을 비교한 결과 기존공식이 지지력을 보수적으로 평가하고 있는 것으로 나타났다. 제안된 공식은 기존공식에 비해 지지력은 선단 15%, 주면 20% 더 높게 (qt=230Pdriven(kN/m2), fmax=3.0NsE(kN/m2)) 평가되는 것으로 확인되었다. 제안식은 여타 현장에 대해 재하시험 결과와 검증을 수행하였으며, 검증 과정에서 제안된 공식이 기존 공식보다 정확히 평가하는 것으로 나타났다.

Keywords

Acknowledgement

본 연구는 국토교통부/국토교통과학기술진흥원을 통하여 지원된 건설기술연구사업 '케이블 교량 글로벌경쟁력 강화를 위한 전주기 엔지니어링 가설공법 개발(20SCIP-B119947-05)'과 정부(교육부)의 재원으로 '한국연구재단의 기초연구사업(2018R1A6A1A08025348)'의 지원을 받아 수행되었으며, 이에 감사드립니다.

References

  1. AIJ (2004), Recommendations for design of building foundations, Architectural Institute of Japan, Tokyo.
  2. American Society for Testing and Materials D1143-87. (2009). Standard Test Method for Piles Under Static Axial Compressive Load.
  3. Boresi, A. (1965), "Elasticity in engineering mechanics", Prentice Hall, N.J.
  4. Briaud, J.L., Jeong, S., and Bush R. (1991), "Group Effect in the Case of Downdrag", Geotechnical Engineering Congress, Geotechnical Special Publication, No.27, pp.505-518.
  5. Broms, B. (1979), "Negative Skin Friction", Proceedings of the 6th Asian Regional Conference of Soil Mechanics and Foundation Engineering, Singapore, Vol.2, pp.41-75.
  6. De Beer, E. (1986), "Different behavior of Bored and Driven Piles", Proceeding of 6th Danubian Conference on Soil Mechanics and Foundation Engineering, pp.307-318.
  7. Ghionna, N., Jamiolkowski, M., Lancellotta, R., and Pedroni, S. (1993), "Base Capacity of Bored Piles in Sands from in Situ Tests", Proceeding of 2nd International Geotechnical Seminar on Deep Foundation on Bored and Auger Piles, A. A. Balkema, Rotterdam, Brookfield, pp.67-75.
  8. Jeong, S., Ahn, S., and Seol, H. (2010), "Shear Load Transfer Characteristics of Drilled Shafts in Rocks", Rock Mechanics and Rock Engineering, Vol.43, No.1, pp.41-54. https://doi.org/10.1007/s00603-009-0026-4
  9. Jeong, S. and Kim, D. (2018), "Estimation of the Load Sharing Ratio of Pre-installed Columns in Top-down Buildings on Korean Rock", KSCE Journal of Civil Engineering, Vol.22, No.12, pp. 4852-4861. https://doi.org/10.1007/s12205-017-1102-z
  10. Johnston, I. and Lam, T. (1989), "Shear behavior of Regular Triangular Concrete/rock Joints-analysis", ASCE Journal of Geotechnical Engineering, Vol.115, No.5, pp.711-727. https://doi.org/10.1061/(ASCE)0733-9410(1989)115:5(711)
  11. Jung, G., Kim, D., Lee, C., and Jeong, S. (2017), "Analysis of Skin Friction behavior in Prebored and Precast Piles based on Field Loading Test", Journal of Korean Geotechnical Society, Vol.33, pp.31-38. https://doi.org/10.7843/kgs.2017.33.1.31
  12. Kim, D. (2018), "Proposed Shaft Resistance of Prebored and Precast Pile using Field Loading Test", Doctoral Dissertation, Yonsei University, Seoul, Korea.
  13. Kim, D., Park, J., Chang, Y., and Jeong, S. (2018), "Proposed Shear Load-transfer Curves for Prebored and Precast Steel Piles", Journal of the Korean Geotechnical Society, Vol.34, No.12, pp.43-58 https://doi.org/10.7843/KGS.2018.34.12.43
  14. Kim, D., Jeong, S., Jung, G., and Park, J. (2018), "Load-sharing Ratio of Prebored and Precast Pile in Top-down Method Construction Process", Structural Design of Tall and Special Buildings, Vol.27, No.10, pp.1-14 (doi: 10.1002/tal.1472).
  15. Kim, D., Jeong, S., and Park, J. (2020), "Analysis on Shaft Resistance of the Steel Pipe Prebored and Precast Piles based on Field Load-transfer Curves and Finite Element Method", Soils and Foundations, Vol.60, No.2, pp.478-495 (https://doi.org/10.1016/j.sandf.2020.03.011).
  16. Kim, S., Jeong, S., Cho, S., and Park, I. (1999), "Shear Load Transfer Characteristics of Drilled Shafts in Weathered Rocks", ASCE Journal of Geotechnical and Geoenvironmental Engineering, Vol.125, No.11, pp.999-1010. https://doi.org/10.1061/(ASCE)1090-0241(1999)125:11(999)
  17. Korean Land and Housing Corporation Structural Design Manual (2008), Korean Land and Housing Corporation, Jinju, Korea.
  18. Setting up Design Criteria of Bored Pile for Bridge Foundations as Enforcement of Limit State Design (2018), Korean Land and Housing Corporation, Jinju, Korea.
  19. Korean Geotechnical Society. (2018), Standards for Foundation Design of Structures, CIR.
  20. Korean Structure Foundation Design Standards (2018), Korean Geotechnical Society, Seoul, Korea.
  21. Ministry of Land, Infrastructure and Transportation (2014), Infrastructure R&D report on PHC prebored and precast piles, Seoul, Korea.
  22. Ng, C., Zhang, L., and Nip, D. (2001), "Response of Laterally Loaded Large-Diameter Bored Pile Groups", ASCE Journal of Geotechnical and Geoenvironmental Engineering, Vol.127, No.8, pp.658-669. https://doi.org/10.1061/(ASCE)1090-0241(2001)127:8(658)
  23. O'Neill, M., Townsend, F., Hassan, K., Buller, A., and Chan, P. (1996), "Load Transfer for Drilled Shafts in Intermediate Geomaterials", Federal Highways Administration.
  24. Park, J. (2004), "Strength and Friction behavior of Cement Paste Pou red in the Bored Pile", Journal of the Korean Geoenvironmental Society, Vol.5, No.3, pp.31-39.
  25. Reese, L. and O'Neill, M. (1988), "Drilled Shafts: Construction Procedures and Design Methods", Publication No. FHWA-HI-88-042, Federal Highway Administration, Washington, D.C.
  26. Seol, H., Jeong, S., and Cho, S. (2009), "Analytical Method for Load-transfer Characteristics of Rock-socketed Drilled Shafts", ASCE's Journal of Geotechnical and Geoenvironmental Engineering, Vol.135, No.6, pp.778-789. https://doi.org/10.1061/(ASCE)1090-0241(2009)135:6(778)
  27. Woo, G., Park, J., Seo, M., and Lee, J. (2016), "Evaluation of Allowable Bearing Capacity of 600 mm Diameter Preboring PHC Piles Using Dynamic Load Test", Journal of the Korean Geotechnical Society, Vol.32, No.11, pp.61-72. https://doi.org/10.7843/kgs.2016.32.11.61
  28. Yamagata, K., Ito, A., Tanaka, T., and Kuramoto, Y. (1992), "Statistical Study on Ultimate Point Load and Point Load-settlement Characteristics of Bored Precast Piles", AIJ Journal of Structural and Construction Engineering, Vol.436, No.6, pp.778-789.
  29. Yun, J., Yea, G., Kim, H., and Choi, Y. (2019), "Case Study on Design Efficiency and Bearing Capacity Characteristics of Bored PHC Piles", Journal of Korean Geosynthetics Society, Vol.18, No.3, pp.45-53.