Journal of the Korea Academia-Industrial cooperation Society (한국산학기술학회논문지)

The Korea Academia-Industrial cooperation Society (한국산학기술학회)
권호 표지
DOI QR코드

DOI QR Code

Study on Bearing Capacity of Ultra High Strengh End Extended PHC Pile by Loading Test

재하시험을 통한 초고강도 선단확장 PHC말뚝의 적용성 연구

  • 황의성 (서울시립대학교 토목공학과)
  • Received : 2018.12.31
  • Accepted : 2019.03.08
  • Published : 2019.03.31
Download PDF
⟨ Previous Next ⟩

Abstract

As the national industry is developing gradually due to the expansion of the economic scale, the construction of large and super high-rise structures for building social infrastructure has been increasing, and studies have been conducted actively to transmit the large loads at the upper portion to the lower bedrock. In this study, the PHC was extended to an ultra-high strength PHC, which increased the concrete compressive strength of the PHC from the conventional 80 MPa to 110 MPa, and the PHC, which extended the tip of the pile. After construction with the driving method and injected pile method, the tendency of the bearing capacity was tested through a load test. Measurements of the bearing capacity of the extended PHC using the pile driving method revealed the main surface friction force to be smaller than that of the general PHC, and the stet-up effect was also insignificant. On the other hand, the effect of the friction force on the ground surface when the injected pile method was applied is expected to increase the bearing capacity when the gap between the main surface and the ground is wide and the cement paste is filled tightly. In addition, the ultrahigh strength PHC showed higher bearing capacity than the conventional PHC, and the permissible pile stress was less than 60%. Therefore, it is possible to reduce the number of piles and reduce the construction cost and effect of shortening the length of the pile by designing the tip of the pile on the ground with the intensity of soft rock as a method for utilizing the increased strength of the ultra-high strength PHC.

경제 규모의 확장으로 국가 산업이 점차 발전해 나갈수록 사회 인프라를 구축하기 위한 대형 초고층 구조물의 건설이 증가함에 따라 상부의 큰하중을 하부의 암반지지층까지 안전하게 전달할 수 있는 연구가 활발히 이루어지고 있다. 본 연구에서는 우리나라의 단단한 암반층을 활용하여 지지력을 극대화 할 수 있도록 PHC의 콘크리트 압축강도를 기존 80 MPa에서 110 MPa로 높인 초고강도PHC에, 말뚝의 선단을 확장시킨 선단확장PHC를 항타공법과 매입공법으로 시공한 후 재하시험을 통해 지지력의 경향성을 확인해 보았다. 항타공법을 사용하여 선단확장PHC의 지지력을 측정해 본 결과 주면마찰력이 일반 PHC에 비해 작게 나타났으며, Stet-up 효과도 미미하게 나타나 지지력 측면에서 우위를 가질 수 없었다. 그러나 매입공법 적용시 주면마찰력의 발휘 효과는 주면부와 지반의 간격이 넓어 시멘트페이스트가 밀실히 채워질 경우 지지력 증가효과가 기대된다. 또한 초고강도PHC가 일반PHC에 비해 높은 지지력이 나타났으며, 허용항타응력도 60% 이내로 나타나 좀 더 견고한 지반까지 안전한 시공이 가능하였다. 따라서 초고강도PHC의 높아진 강도를 활용하기 위해서는 말뚝의 선단부를 연암의 강도를 지닌 지반에 설계하는 것이 말뚝 본수를 크게 절감 할 수 있으며, 시공비 절감과 공기단축의 효과도 얻을 수 있을 것이다.

Keywords

SHGSCZ_2019_v20n3_269_f0001.png 이미지

Fig. 1. Various piles of Japan (a) SC Pile (b) Nondular cylinder pile

SHGSCZ_2019_v20n3_269_f0002.png 이미지

Fig. 2. End expansion pile Foreground

SHGSCZ_2019_v20n3_269_f0003.png 이미지

Fig. 5. UФ4550 pile construction foreground

SHGSCZ_2019_v20n3_269_f0004.png 이미지

Fig. 3. Graph of bearing capacity change by time [UФ4550 vs HФ500]

SHGSCZ_2019_v20n3_269_f0005.png 이미지

Fig. 4. Graph of bearing capacity change by time [UФ600 vs HФ600]

Table 1. Types and amounts of pile load tests

SHGSCZ_2019_v20n3_269_t0001.png 이미지

Table 2. Test pile types by construction method

SHGSCZ_2019_v20n3_269_t0002.png 이미지

Table 3. Site investigation results

SHGSCZ_2019_v20n3_269_t0003.png 이미지

Table 4. Allowable bearing capacity by dynamic tests [UФ4550 vs HФ500]

SHGSCZ_2019_v20n3_269_t0004.png 이미지

Table 5. Allowable bearing capacity by dynamic tests [UФ600 vs HФ600]

SHGSCZ_2019_v20n3_269_t0005.png 이미지

Table 6. Allowable bearing capacity by dynamic tests [UФ500 vs HФ500]

SHGSCZ_2019_v20n3_269_t0006.png 이미지

Table 7. Allowable bearing capacity by dynamic tests [UФ5055 vs HФ5055]

SHGSCZ_2019_v20n3_269_t0007.png 이미지

References

  1. Korea Professional Construction Association Scaffolding & Construction Dismantling Construction Industry Council, Advanced pile construction method study, pp.9-22, Korea Professional Construction Association, 2005.
  2. D. J. AN, Structural characteristics of hybrid FRPconcrete, Ph.D dissertation, Hongik University, pp.1-3, 2012.
  3. J. S. Kim, Study on the behavior characteristics of hybrid concrete filled fiber reinforced plastic piles, Ph.D dissertation, Hongik University, pp.1-4, 2013.
  4. J. W. Bang, C. K. Park, S. Y. Yang, Y. Y. Kim, "Flexural Behavior of Large-Diameter Composite PHC pile Using In-Filled Concrete", Journal of The Korea Institute for Structural Maintenance and Inspection, The Korea Institute For Structural Maintenance and Inspection, Seoul, Korea, Vol.20. No.5 pp.109-115, Sep 2016. DOI: https://doi.org/10.11112/jksmi.2016.20.5.109
  5. KOREAN GEOTECHNICAL SOCIETY, Load test method and commentary on foundation, pp.137-152, Goomibook, 2010.
  6. KOREAN GEOTECHNICAL SOCIETY, Explanation of Design Criteria for Structures, p.326, Goomibook, 2009.
  7. KOREAN GEOTECHNICAL SOCIETY, Design and construction of PHC pile, pp.291-293, 2006.