Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
권호 표지
DOI QR코드

DOI QR Code

Evaluation of Soil Disturbance Due to Bucket Installation in Sand

모래지반에서 버켓기초 설치에 의한 지반교란 평가

  • Kim, Jae-Hyun (Dept. of Infrastructure Safety Research, Korea Institute of Civil Engrg. and Building Technology) ;
  • Lee, Seung-Tae (Investment Planning & Engrg. Office, POSCO) ;
  • Kim, Dong-Soo (Dept. of Civil and Environ. Eng., KAIST)
  • 김재현 (한국건설기술연구원 인프라안전연구본부) ;
  • 이승태 (포스코 광양제철소 투자엔지니어링실) ;
  • 김동수 (한국과학기술원 건설및환경공학과)
  • Received : 2018.09.22
  • Accepted : 2018.10.11
  • Published : 2018.11.30
Download PDF
⟨ Previous Next ⟩

Abstract

Bucket foundations are widely used in offshore areas due to their various benefits such as easy and fast installations. A bucket is installed using self-weight and the hydraulic pressure difference across the lid generated by pumping out water from inside the bucket. When buckets are installed in high permeable soil such as sands, upward seepage flow occurs around the bucket tip and interior, leading to a decrease in the effective stress in the soil inside the buckets. This process reduces the penetration resistance of buckets. However, the soil inside and outside the bucket can be disturbed due to the upward seepage flow and this can change the soil properties around the bucket. Moreover, upward seepage flow can create significant soil plug heave, thereby hindering the penetration of the bucket to the target depth. Despite of these problems, soil disturbance and soil plug heave created by suction installation are not well understood. This study aims to investigate the behavior of soil during suction installation. To comprehend the phenomena of soil plug heave during installation, a series of small-scale model tests were conducted with different testing conditions. From a series of tests, the effects of tip thickness of bucket, penetration rate, and self-weight were identified. Finally, soil properties inside the bucket after installation were approximated from the measured soil plug heave.

버켓기초(bucket foundation)는 해상 구조물 지지를 위해 사용되는 구조물로 간편하고 빠르게 지반에 설치할 수 있어 종래의 기초를 대체하여 해양에서 널리 활용되고 있다. 버켓기초는 기초 자중과 버켓 내부의 물을 외부로 배출시킴으로써 발생하는 내외부 압력차를 이용해 설치된다. 버켓기초가 모래지반과 같이 투수성이 높은 지반에 설치될 경우에는 석션압에 의해 버켓 외부지반에서 내부방향으로 침투수류(seepage flow)가 형성된다. 석션압에 의해 발생하는 상향의 침투수류는 내부지반의 유효응력을 감소시켜 버켓기초의 관입저항력을 낮추는 역할을 하지만 내부지반이 연약해 지고융기(heaving)되는 현상이 발생할 수 있다. 이는 버켓기초가 목표 깊이까지 설치되는 것을 저해하고 장기거동에 영향을 줄 수 있다. 하지만 현재까지도 이에 대한 연구가 미진한 실정이다. 따라서 본 연구에서는 축소모형실험을 통해 버켓기초 설치 중 발생하는 석션압과 지반 교란현상을 실험적으로 평가하였다. 이를 위해 버켓기초의 선단부 두께, 관입속도와 자중이 각각 석션설치 및 지반교란에 미치는 영향을 실험적으로 확인하고 교란된 지반의 물성을 추정하였다.

Keywords

GJBGC4_2018_v34n11_21_f0001.png 이미지

Fig. 1. Experimental setup of suction bucket installation test

GJBGC4_2018_v34n11_21_f0002.png 이미지

Fig. 2. Comparison of jacking and suction installation

GJBGC4_2018_v34n11_21_f0003.png 이미지

Fig. 3. Installations with different wall thickness: (a) suction pressure with depth; (b) seepage flow with depth

GJBGC4_2018_v34n11_21_f0004.png 이미지

Fig. 4. soil plug heave with different wall thickness

GJBGC4_2018_v34n11_21_f0005.png 이미지

Fig. 5. Installations with different flow rate: (a) suction pressure with depth; (b) seepage flow with depth

GJBGC4_2018_v34n11_21_f0006.png 이미지

Fig. 6. soil plug heave with different flow rate

GJBGC4_2018_v34n11_21_f0007.png 이미지

Fig. 7. Installations with self weight: (a) suction pressure with depth; (b) soil plug heave

GJBGC4_2018_v34n11_21_f0008.png 이미지

Fig. 8. Variation of permeability ratio due to suction installation

Table 1. Geotechnical properties of tested soils (after Kim et al., 2016)

GJBGC4_2018_v34n11_21_t0001.png 이미지

Table 2. Testing conditions

GJBGC4_2018_v34n11_21_t0002.png 이미지

References

  1. Allersma, H.G.B., Plenevaux, F.J.A., and Wintgens, J.F. (1997), "Simulation of Suction Pile Installation in Sand in a Geocentrifuge", Proceedings of the 7th International Offshore and Polar Engineering Conference, Honolulu, USA, pp.761-766.
  2. Andersen, K.H., Murff, J.D., Randolph, M.F., Clukey, E.C., Erbrich, C.T., Jostad, H.P., Hansen, B., Aubeny, C., Sharma, P., and Supachawarote, C. (2005), "Suction Anchors for Deepwater Applications", Proceeding of International Symposium on Frontiers in Offshore Geotechnics, Perth, Australia, pp.3-30.
  3. Andersen, K.H., Jostad, H.P., and Dyvik, R. (2008), "Penetration Resistance of Offshore Skirted Foundations and Anchors in Dense Sand", Journal of Geotechnical and Geoenvironmental Engineering, Vol.134, No.1, pp.106-116. https://doi.org/10.1061/(ASCE)1090-0241(2008)134:1(106)
  4. American Society for Testing and Materials (ASTM). (2006), "Standard Test Method for Minimum Index Density and Unit Weight of Soils and Calculation of Relative Density", ASTM D4254-00, West Conshohoken, PA.
  5. American Society for Testing and Materials (ASTM). (2011), "Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)", ASTM D2487-11, West Conshohoken, PA.
  6. American Society for Testing and Materials (ASTM). (2014), "Standard Test Methods for Maximum Index Density and Unit Weight of Soils Using a Vibratory Table", ASTM D4253-14, West Conshohoken, PA.
  7. Bang, S., Cho, Y., Preber, T., and Thomason, J. (1999), "Model Testing and Calibration of Suction Pile Installation in Sand", Proceedings of the 11th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, Seoul, Korea, pp.235-256.
  8. Bang, S., Preber, T., Cho, Y., Thomason, J., Karnoski, S.R., and Taylor, R.J. (2000), "Suction Piles for Mooring of Mobile Offshore Bases", Marine Structures, Vol.13, No.5. pp.367-382. https://doi.org/10.1016/S0951-8339(00)00012-5
  9. Cotter, O. (2010), "Installation of Suction Caisson Foundations for Offshore Renewable Energy Structures", PhD thesis, Oxford University, UK.
  10. Erbrich, C.T. and Tjelta, T.I. (1999), "Installation of Bucket Foundations and Suction Caissons in Sand-geotechnical Performance", Offshore Technology Conference, Houston, USA, paper OTC 10990.
  11. Houlsby, G.T. and Byrne, B.W. (2005), "Design Procedures for Installation of Suction Caissons in Sand", Proceedings of the Institution of Civil Engineers. Geotechnical Engineering, Vol.158, No.3, pp.135-144. https://doi.org/10.1680/geng.2005.158.3.135
  12. Iskander, M., El-Gharbawy, S., and Olson, R. (2002), "Performance of Suction Caissons in Sand and Clay", Canadian Geotechnical Journal, Vol.39, No.3, pp.576-584. https://doi.org/10.1139/t02-030
  13. Kim, J.H. (2016), "Model Testing of Bucket Foundations for Offshore Structure in the Centrifuge and Development of Miniature Cone", PhD thesis, Korea Advanced Institute of Science and Technology (KAIST), Korea.
  14. Kim, J.H., Choo, Y.W., Kim, D.J., and Kim, D.S. (2016), "Miniature Cone Tip Resistance on Sand in a Centrifuge", Journal of Geotechnical and Geoenvironmental Engineering, Vol.142, No.3, 04015090. https://doi.org/10.1061/(ASCE)GT.1943-5606.0001425
  15. Kim, J.H., Lee, S.T., and Kim, D.S. (2017), "Observation of Sand Movement during Bucket Installation", International Journal of Physical Modelling in Geotechnics (ahead of print).
  16. Kumara, J. J., Kikuchi, Y., and Kurashina, T. (2016), "Effects of the Lateral Stress on the Inner Frictional Resistance of Pipe Piles Driven into Sand", International Journal of Geo-Engineering, Volume 7, Paper no. 1, DOI 10.1186/s40703-016-0015-x
  17. Larsen, K.A., Ibsen, L.B., and Barari, A. (2013), "Modified Expression for the Failure Criterion of Bucket Foundations Subjected to Combined Loading", Canadian Geotechnical Journal, Vol.50, No.12, pp.1250-1259. https://doi.org/10.1139/cgj-2012-0308
  18. Senpere, D. and Auvergne, G.A. (1982), "Suction Anchor Piles - A Proven Alternative to Driving or Drilling", Offshore Technology Conference, Houston, USA, Paper OTC 4206.
  19. Tjelta, T.I. (1995), "Geotechnical Experience from the Installation of the Europipe Jacket with Bucket Foundations", Offshore Technology, Conference, Houston, USA, Paper OTC 7795.
  20. Tjelta, T.I., Guttormsen, T.R., and Hermstad, J. (1986), "Large-scale Penetration Test at a Deepwater Site", Offshore Technology Conference, Houston, USA, Paper OTC 5103.
  21. Tran, M.N. (2005), "Installation of Suction Caissons in Dense Sand and the Influence of Silt and Cemented Layers", PhD thesis, University of Sydney, Australia.
  22. Tran, M.N. and Randolph, M.F. (2008), "Variation of Suction Pressure during Caisson Installation in Sand", Geotechnique, Vol.58, No.1, pp.1-11. https://doi.org/10.1680/geot.2008.58.1.1
  23. Tran, M.N., Randolph, M.F., and Airey, D.W. (2005), "Study of Seepage Flow and Sand Plug Loosening in Installation of Suction Caissons in Sand", Proceeding of the 15th International Offshore and Polar Engineering Conference (ISOPE), Seoul, Korea, pp. 516-521.
  24. Villalobos, F. (2007), "Installation of Suction Caissons in Sand", Proceeding of 6th Chilean Conference of Geotechnics.

Cited by

  1. 실트질 모래지반에 설치된 해상풍력 석션버켓기초의 신뢰성 해석 vol.20, pp.12, 2019, https://doi.org/10.14481/jkges.2019.20.12.41
  2. 모형실험을 활용한 저수심 사질토 지반에서 원형강관 설치 석션압 평가 vol.22, pp.2, 2021, https://doi.org/10.5762/kais.2021.22.2.1