Journal of Korean Society of Coastal and Ocean Engineers (한국해안·해양공학회논문집)

Korean Society of Coastal and Ocean Engineers (한국해안·해양공학회)
권호 표지
DOI QR코드

DOI QR Code

Numerical Analysis on Liquefaction Countermeasure of Seabed under Submerged Breakwater Using Concrete Mat Cover (for Irregular Waves)

콘크리트매트 피복을 이용한 잠제하 해저지반에서의 액상화 대책공법에 관한 수치해석 (불규칙파 조건)

  • Lee, Kwang-Ho (Dept. of Energy Resources and Plant Eng., Catholic Kwandong University) ;
  • Ryu, Heung-Won (Dept. of Civil and Environmental Eng., Graduate School, Korea Maritime and Ocean University) ;
  • Kim, Dong-Wook (Dept. of Civil and Environmental Eng., Graduate School, Korea Maritime and Ocean University) ;
  • Kim, Do-Sam (Dept. of Civil Eng., Korea Maritime and Ocean Univ.) ;
  • Kim, Tae-Hyung (Dept. of Civil Eng., Korea Maritime and Ocean Univ.)
  • 이광호 (가톨릭관동대학교 에너지자원플랜트공학과) ;
  • 류흥원 (한국해양대학교 대학원 토목환경공학과) ;
  • 김동욱 (한국해양대학교 대학원 토목환경공학과) ;
  • 김도삼 (한국해양대학교 건설공학과) ;
  • 김태형 (한국해양대학교 건설공학과)
  • Received : 2017.01.12
  • Accepted : 2017.02.20
  • Published : 2017.02.28
Download PDF
⟨ Previous Next ⟩

Abstract

In the case of the seabed around and under gravity structures such as submerged breakwater is exposed to a large wave action long period, the excess pore pressure will be significantly generated due to pore volume change associated with rearrangement soil grains. This effect will lead a seabed liquefaction around and under structures as a result of the decrease in the effective stress, and eventually the possibility of structure failure will be increased. The study of liquefaction potential for regular waves had already done, and this study considered for irregular waves with the same numerical analysis method used for regular waves. Under the condition of the irregular wave field, the time and spatial series of the deformation of submerged breakwater, the pore water pressure (oscillatory and residual components) and pore water pressure ratio in the seabed were estimated and their results were compared with those of the regular wave field to evaluate the liquefaction potential on the seabed quantitatively. Although present results are based on a limited number of numerical simulations, one of the study's most important findings is that a safer design can be obtained when analyzing case with a regular wave condition corresponding to a significant wave of the irregular wave.

잠제와 같은 중력식구조물 하부 해저지반에 고파랑이 장시간 작용하는 경우 토립자내 간극의 체적변화를 일으키는 과정에서 과잉간극수압이 크게 발생될 수 있고, 이에 따른 유효응력의 감소에 의하여 구조물 근방 및 하부의 해저지반에 액상화가 발생될 수 있으며, 종국에는 구조물이 침하파괴될 가능성이 있다. 또한, 액생화를 방지하기 위한 대책공법으로 규칙파의 경우 콘크리트매트를 해저지반상에 포설하여 구조물의 동적변위 및 지반내 간극 수압 및 간극수압비가 감소하는 것을 규명하였다. 본 연구에서는 실해역을 모사한 불규칙파랑을 대상으로 규칙파 해석에서 적용된 동일한 수치해석법을 적용하여 잠제의 동적변위 및 해저지반내 간극수압, 간극수압비 등과 같은 지반거동의 시 공간변화를 규칙파의 경우와 대비하면서 액상화 가능성을 검토하였다. 이로부터 불규칙파동장하에서도 콘크리트매트하의 해저지반내에서 액상화 가능성을 크게 줄일 수 있고, 한정된 본 결과이지만 콘크리트매트가 포설된 경우에도 액상화 평가시 불규칙파의 유의파에 해당하는 파랑조건을 적용한 규칙파 해석이 더욱 안정적인 설계로 된다는 것을 확인할 수 있었다.

Keywords

References

  1. Biot, M.A. (1941). General theory of three-dimensional consolidation, J. of Applied Physics, 12, 155-165. https://doi.org/10.1063/1.1712886
  2. CDIT(2001). Research and development of numerical wave channel( CADMAS-SURF), CDIT library, 12.
  3. Goda, Y. (2010). Random seas and design of maritime structures, World Scientific.
  4. Godbold, J., Sackmann, N. and Cheng, L. (2014). Stability design for concrete mattresses, Proceedings of 24 th International Ocean and Polar Engineering Conference, ISOPE, 302-308.
  5. Hirt, C.W. and Nichols, B.D. (1981). Volume of fluid(VOF) method for the dynamics of free boundaries, J. of Computational Physics, 39, 201-225. https://doi.org/10.1016/0021-9991(81)90145-5
  6. Hsu, T.J., Sakakiyama, T., and Liu, P.L.F. (2002). A numerical model for wave motions and turbulence flows in front of a composite breakwater. Coastal Engineering, 46(1), 25-50. https://doi.org/10.1016/S0378-3839(02)00045-5
  7. Iai, S., Matsunaga, Y. and Kameoka, T. (1992a). Strain space plasticity model for cyclic mobility, Soils and Foundations, Japanese Society of Soil Mechanics and Foundation Eng., 32(2), 1-15.
  8. Iai, S., Matsunaga, Y. and Kameoka, T. (1992b). Analysis of undrained cyclic behavior of sand under anisotropic consolidation, Soils and Foundation, Japanese Society of Soil Mechanics and Foundation Eng., 32(2), 16-20.
  9. Jeng. D.S., Ye, J.H., Zhang, J.S., and Liu, P.F. (2013). An integrated model for the wave-induced seabed response around marine structures : Model verifications and applications. Coastal Engineering, 72, 1-19. https://doi.org/10.1016/j.coastaleng.2012.08.006
  10. Lee, K.H., Park, J.H., and Kim, D.S. (2012). Numerical simulation of irregular airflow within wave power converter using OWC by action of 3-dimensional irregular waves, J. of Korean Society of Coastal and Ocean Engineers, 24(3), 189-202 (in Korean). https://doi.org/10.9765/KSCOE.2012.24.3.189
  11. Lee, K.H., Park, J.H., Cho, S. and Kim, D.S. (2013). Numerical simulation of irregular airflow in OWC generation system considering sea water exchange, J. of Korean Society of Coastal and Ocean Engineers, 25(3), 128-137 (in Korean). https://doi.org/10.9765/KSCOE.2013.25.3.128
  12. Lee, K.H., Ryu, H.W., Kim, D.W, Kim, D.S. and Kim, T.H. (2016a). Regular waves-induced seabed dynamic responses around submerged breakwater, J. of Korean Society of Coastal and Ocean Engineers, 28(3), 132-145 (in Korean). https://doi.org/10.9765/KSCOE.2016.28.3.132
  13. Lee, K.H., Ryu, H.W., Kim, D.W, Kim, D.S. and Kim, T.H. (2016b). Irregular waves-induced seabed dynamic responses around submerged breakwater, J. of Korean Society of Coastal and Ocean Engineers, 28(4), 177-190 (in Korean). https://doi.org/10.9765/KSCOE.2016.28.4.177
  14. Lee, K.H., Ryu, H.W., Kim, D.W, Kim, D.S. and Kim, T.H. (2016c). Numerical analysis on liquefaction countermeasure of seabed under submerged breakwater using concrete mat cover (for regular waves), J. of Korean Society of Coastal and Ocean Engineers, 28(6), 361-374 (in Korean). https://doi.org/10.9765/KSCOE.2016.28.6.361
  15. Losada, I.J., Silva, R. and Losada, M.A. (1996). 3-D non-breaking regular wave interaction with submerged breakwaters, Coastal Engineering, 28, 229-248. https://doi.org/10.1016/0378-3839(96)00019-1
  16. Mitsuyasu, H. (1970). On the growth of spectrum of wind-generated waves (2)-spectral shape of wind waves at finite fetch, Proc. 17 th Japanese Conf. Coastal Eng., 1-7 (in Japanese).
  17. Mizutani, N., Mostafa, A.M. and Iwata, K. (1998). Nonlinear regular wave, submerged breakwater and seabed dynamic interaction. Coastal Engineering, 33, 177-202. https://doi.org/10.1016/S0378-3839(98)00008-8
  18. Morita, T., Iai, S., Hanlong, L., Ichii, Y. and Satou, T. (1997). Simplified set-up method of various parameters necessary to predict liquefaction damage of structures by FLIP program, Technical Note of the Port and Harbour Research Institute Ministry of Transport, PARI, Japan, 869, 1-36.
  19. Sakakiyama, T. and Kajima, R. (1992). Numerical simulation of nonlinear wave interaction with permeable breakwater, Proceedings of the 22nd ICCE, ASCE, 1517-1530.
  20. Sekiguchi, H., Sassa, S., Miyamoto, J. and Sugioka, K. I. (2000). Wave-induced liquefaction, flow deformation and particle transport in sand beds, ISRM International Symposium, International Society for Rock Mechanics.
  21. Sumer, B. M., Dixen, F. H. and Fredsoe, J. (2010). Cover stones on liquefiable soil bed under waves. Coastal Engineering, 57(9), 864-873. https://doi.org/10.1016/j.coastaleng.2010.05.004
  22. Yasuda, S. (1988). From investigation to countermeasure for liquefaction, Kajima Press, 256p (in japanese).