Journal of the Korean Geosynthetics Society (한국지반신소재학회논문집)

Korean Geosynthetics Society (한국지반신소재학회)
권호 표지
DOI QR코드

DOI QR Code

Analysis of Helical Pile Behavior in Sands Varying Helix Pitch Based on Numerical Analysis Results

사질토에 근입된 헬릭스 피치에 따른 헬리컬 파일의 수치해석적 거동분석

  • Bak, Jongho (Department of Civil and Environmental Engineering, Incheon National University) ;
  • Lee, Kicheol (Department of Civil and Environmental Engineering, Incheon National University) ;
  • Choi, Byeong-Hyun (Department of Civil and Environmental Engineering, Incheon National University) ;
  • Kim, Dongwook (Department of Civil and Environmental Engineering, Incheon National University)
  • Received : 2018.10.23
  • Accepted : 2018.11.08
  • Published : 2018.12.30
Download PDF
⟨ Previous Next ⟩

Abstract

Oil sands, which are largely distributed in Canada and Venezuela, are a mixture of crude oil and sandy soils. In order to extract crude oil from oil sands, construction of massive oil sand plants is required. Generally, the typically-used foundation types of the oil sand plant are driven piles and cast-in-place piles. Most of the oil sand plants are located in cold and remote regions. Installation of driven piles in frozen or organic surface soils is difficult due to high resistance and installation equipment accessability, while the cast-in-place pile has concrete curing problem due to cold temperature. Helical pile can be installed quickly and easily using rotation with a little help of vertical load. As the installation of helical pile is available using a small and light-weight installation equipment, accessibility of installation equipment is improved. The helical pile has an advantage of easy removal by rotation in reverse direction compared with that of installation. Furthermore, reuse of removed helical piles is possible when the piles are structurally safe. In this study, the behavior of helical piles varying helix pitch was analyzed based on the numerical analysis results. Numerical model was calibrated based on the results of model helical pile tests in laboratory. The ultimate helical pile loads, the displacement of each helix attached to the shaft of the helical pile, and the load sharing ratio of each helix were analyzed.

캐나다 및 베네수엘라에 주로 분포하는 오일샌드는 원유들이 모래질 흙의 간극에 존재한다. 이러한 오일샌드로부터 원유를 따로 추출하기 위해서는 규모가 큰 플랜트를 건설해야 한다. 일반적으로 오일샌드 플랜트의 기초는 주로 항타말뚝 혹은 현장타설말뚝이 사용되고 있다. 하지만 주로 극지에 위치한 오일샌드는 얼어있는 지반과 표층의 유기토 때문에 항타말뚝의 시공 및 장비 진입에 어려움이 있으며, 현장타설말뚝의 경우 기온이 낮기 때문에 콘크리트 양생에 문제가 있다. 이번 연구의 주제인 헬리컬 파일은 크지 않은 연직력에 기초한 회전력을 중심으로 빠르고 간편하게 시공이 가능하다. 따라서, 접근성이 떨어지는 극지환경에서도 소형장비를 사용하여 간단한 시공이 가능하며, 헬리컬 파일의 두부에 역회전을 가해 말뚝기초의 인발 및 재사용 또한 용이하다. 이번 연구에서는 헬릭스 피치를 변화시켜 헬리컬 파일 및 헬릭스의 거동을 수치해석으로 분석하였다. 수치해석의 검증은 모형 헬리컬 파일의 실내모형실험 결과와 비교하여 수행하였으며, 헬릭스의 피치에 따른 헬리컬 파일의 극한하중, 헬리컬 파일의 축에 부착한 각 헬릭스의 변위, 하중분담률을 분석하였다.

Keywords

HKTHB3_2018_v17n4_29_f0001.png 이미지

Fig. 1. Schematic of a helical pile [modified after Carol and Roy (2018)]

HKTHB3_2018_v17n4_29_f0002.png 이미지

Fig. 2. Load-Settlement curve of helical pile (modified after Kulhawy, 2004)

HKTHB3_2018_v17n4_29_f0003.png 이미지

Fig. 4. Sand pluviator; (a) Schematic of sand pluviator and (b) Relationship between relative density and falling height of sand (modified after Lee et al., 2017)

HKTHB3_2018_v17n4_29_f0004.png 이미지

Fig. 5. Modeling used in the numerical analysis: (a) integrated model of ground and pile and important dimensions and (b) enlarged helical pile model and its dimensions

HKTHB3_2018_v17n4_29_f0005.png 이미지

Fig. 6. Comparison of laboratory model test and numerical analysis

HKTHB3_2018_v17n4_29_f0006.png 이미지

Fig. 7. Four different pitches of helical piles (units in mm): Helix pitch equal to (a) 25 mm (0.5D), (b) 50 mm (1D), and (c) 75 mm (1.5D)

HKTHB3_2018_v17n4_29_f0007.png 이미지

Fig. 8. Load-settlement curves of helical piles with different helix pitches and the ultimate loads by different criteria

HKTHB3_2018_v17n4_29_f0008.png 이미지

Fig. 9. Linear, transition, and final linear regions from load-settlement curves varying helix pitches: helix pitch of (a) 25 m m (0.5D), (b) 50 mm (1D), and (c) 75 mm (1.5D)

HKTHB3_2018_v17n4_29_f0010.png 이미지

Fig. 11. Load sharing ratio with pitch of helix

HKTHB3_2018_v17n4_29_f0011.png 이미지

Fig. 3. (a)　Soil chamber and　(b) helical pile and their dimensions used for laboratory model test

HKTHB3_2018_v17n4_29_f0012.png 이미지

Fig. 10. Displacement of each helix with load at pile head; pitch of helix is (a) 25 mm (0.5D), (b) 50 mm (1D) and (c) 75 mm (1.5D)

Table 1. Estimation method of ultimate load of helical pile by researchers

HKTHB3_2018_v17n4_29_t0001.png 이미지

Table 2. Physical properties of crushed sands used in this study (Lee et al., 2017)

HKTHB3_2018_v17n4_29_t0002.png 이미지

Table 3. Material properties used for numerical analysis

HKTHB3_2018_v17n4_29_t0003.png 이미지

Table 4. Ultimate loads and the corresponding settlements for different helix pitches

HKTHB3_2018_v17n4_29_t0004.png 이미지

Table 5. Loads and corresponding settlements of turning points from linear to transition regions and those from transition to final linear regions

HKTHB3_2018_v17n4_29_t0005.png 이미지

Table 6. Average displacement of each helix when the equivalent load is applied

HKTHB3_2018_v17n4_29_t0006.png 이미지

References

  1. Abramov, O. V., Abramov, V. O., Myasnikov, S. K. and Mullakaev, M. S. (2009), "Extraction of Bitumen, Crude Oil and its Products from Tar Sand and Contaminated Sandy Soil under Effect of Ultrasound", Ultrasonics Sonochemistry, Vol.16, No.3, pp.408-416. https://doi.org/10.1016/j.ultsonch.2008.10.002
  2. Carol, M. and Roy, R. M. (2018), "Ultimate Load Bearing Capacity and Settlement of Triangular Screw Pile based on Desing Parameter", International Research Journal of Engineering and Technology, Vol.5, Issue.6, pp.475-477.
  3. Cho, C. (2007), "Next Decade of Pile Foundation in Korea", Journal of Korean Society of Civil Engineers, Vol.55, No.1, pp.74-83. (in Korean)
  4. Davisson, M. T. (1973). High Capacity Piles. Proceeding of the Lecture Series, Innovaions in Foundations Construcion. Illinois, ASCE.
  5. Elkasabgy, M. and El Naggar, M. H. (2014), "Axial Compressive Response of Large-CapacityHelical and Driven Steel Piles in Cohesive Soil", Canadian Geotechnical Journal, Vol.52, No.2, pp.224-243. https://doi.org/10.1139/cgj-2012-0331
  6. Helical Anchors, Inc., 2014, "Engineering Design Manual".
  7. Japanese Industrial Standards (JIS), (2009), Test method for minimum and maximum densities of sands, A 1224, Japanese Industrial Standards, Tokyo, Japanese.
  8. Korean Agency for Technology and Standards (KATS) (2002), The method for particle size distribution of soils, F 2302, Korean Agency for Technology and Standards, Chungcheongbuk-do, Korea.
  9. Korean Agency for Technology and Standards (KATS) (2007), Testing method for direct shear test of soils under consolidated drained conditions, F 2343, Korean Agency for Technology and Standards, Chungcheongbuk-do, Korea.
  10. Korean Agency for Technology and Standards (KATS) (2016), Standard test method for density of soil particles, F 2308, Korean Agency for Technology and Standards, Chungcheongbuk-do, Korea.
  11. Kulhawy, F. H. (2004), "On the Axial Behaviour of Drilled Foundations". American Society for Civil Engineering", GeoSupport Conference 2004:Drilled Shafts, Micropiling, Deep Mixing, Remedial Methods, and Specialty Foundation System, Florida, pp.34-51.
  12. Kurian, N. P. and Shah, S. J. (2009), "Studies on the Behaviour of Screw Piles by the Finite Element Method", Canadian Geotechnical Journal, Vol.46, No.6, pp.627-638. https://doi.org/10.1139/T09-008
  13. Lee, D., Na, K., Lee, W., Kim, H. N. and Choi, H. (2014), "Applicability of Bi-directional Load Test for Evaluating Bearing Capacity of Helical Piles", Journal of Korean Geosynthetics Society, Vol.13, No.4, pp.77-85. (in Korean) https://doi.org/10.12814/jkgss.2014.13.4.077
  14. Lee, J. (2016), "Construction Technology in Cold Regions", Journal of Korean Architecture and Building Science, Vol.60, No.5, pp.32-36. (in Korean)
  15. Lee, J., Lee, K. and Kim, D. (2017), "Analysis of Axial Capacity and Constructability of Helical Pile with Inner Cone Penetration", Journal of Korean Geosynthetics Society, Vol.16, No.4, pp.1-11. (in Korean) https://doi.org/10.12814/jkgss.2017.16.1.001
  16. Livneh, B. and El Naggar, M. H. (2008), "Axial Testing and Numerical Modeling of Square Shaft Helical Piles under Compressive and Tensile loading", Canadian Geotechnical Journal, Vol.45, No.8, pp.1142-1156. https://doi.org/10.1139/T08-044
  17. O'Neill, M. W. and Reese, L. C. (1999), Drilled Shaft: Construction, procedures and design methods. FHWA-IF-99-025.
  18. Park, K. Y., Han, S. D., Han, H. J., Kang, K. S., Bae, W. and Rhee, Y. W. (2009), "A Study on the Trend of Technology for the Treatment of Oil from Oilsands by Patent Analysis", Journal of Clean Technology, Vol.15, No.3, pp. 210-223. (in Korean)
  19. Park, Y., Choi, W. C., Jeong, S. Y. and Lee, C. W (2007), "High Value-added Technology of Oil Sand", Journal of Korean Chemical Engineering Research, Vol.45, No.2, pp. 109-116. (in Korean)
  20. Rao, S. N., Prasad, Y. V. S. N. and Shetty, M. D. (1991), "The behaviour of model screw piles in cohesive soils", Soils and Foundations, Vol.31, No.2, pp.35-50. https://doi.org/10.3208/sandf1972.31.2_35
  21. Sakr, M. (2009), "Performance of Helical Piles in Oil Sand", Canadian Geotechnical Journal, Vol.46, No.9, pp.1046-1061. https://doi.org/10.1139/T09-044
  22. Sakr, M. (2011), "Installation and Performance Characteristics of High Capacity Helical Piles in Cohesionless Soils", The Journal of the Deep Foundations Institute, Vol.5, No.1, pp. 39-57. https://doi.org/10.1179/dfi.2011.004
  23. SIMULIA (2014), 6.14 Documentation Collection, ABAQUS/CAE User' Manual.