DOI QR코드

DOI QR Code

Scour around vertical piles due to random waves alone and random waves plus currents on mild slopes

  • Received : 2015.11.17
  • Accepted : 2016.05.07
  • Published : 2016.06.25

Abstract

This paper provides a practical stochastic method by which the maximum equilibrium scour depth around a vertical pile exposed to random waves plus a current on mild slopes can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Battjes and Groenendijk (2000) wave height distribution for mild slopes including the effect of breaking waves, and using the empirical formulas for the scour depth on the horizontal seabed by Sumer and Fredsøe (2002). The present approach is valid for wave-dominant flow conditions. Results for random waves alone and random wave plus currents have been presented and discussed by varying the seabed slope and water depth. An approximate method is also proposed, and comparisons are made with the present stochastic method. For random waves alone it appears that the approximate method can replace the stochastic method, whereas the stochastic method is required for random waves plus currents. Tentative approaches to related random wave-induced scour cases on mild slopes are also suggested.

Keywords

scour depth;vertical pile;mild slope;random waves;current;stochastic method

References

  1. Abramowitz, M. and Stegun, I.A. (1972), Handbook of Mathematical Functions, Dover, New York.
  2. Battjes, J.A. (1974), "Surf similarity", Proceedings of the 14th Int. Conf. On Coastal Eng., ASCE, New York.
  3. Battjes, J.A. and Groenendijk, H.W. (2000), "Wave height distributions on shallow foreshores", Coast. Eng., 40, 161-182. https://doi.org/10.1016/S0378-3839(00)00007-7
  4. Bijker, E.W. and de Bruyn, C.A. (1988), "Erosion around a pile due to current and breaking waves", Proceedings of the 21st Coastal Engineering Conf., Costa del Sol, Malaga, Spain.
  5. Carreiras, J., Larroude, P., Seabra-Santos, F. and Mony, M. (2000), "Wave scour around piles", Proceedings of the 20th Int. Conf. on Coastal Engineering, Sydney, Australia, ASCE, Reston VA, USA.
  6. Dey, S., Helkjaer, A., Sumer, B.M. and Fredsoe, J. (2011), "Scour at vertical piles in sand-clay mixtures under waves", J. Waterway, Port, Coastal, Ocean Eng., 137(6), 324-331. https://doi.org/10.1061/(ASCE)WW.1943-5460.0000095
  7. Goda, Y. (1979), A review on statistical interpretation of wave data, Report of the Port and Harbour Research Institute, Japan.
  8. Jensen, J.J. (2002), "Conditional short-crested waves in shallow water and with superimposed current", Proceedings of the 21st Int. Conf. on Offshore Mech. and Arctic Eng., Oslo, Norway. Paper No. OMAE2002-28399.
  9. Lillycrop, W.J. and Hughes, S.A. (1993), Scour hole problems experienced by the corps of engineers; data presentation and summary. Miscellaneous papers, US Army Engineer Waterways Experiment Station Coastal Engineering Research Center, Vicksburg, MS, Paper No. CERC-93-2.
  10. Myrhaug, D. (1995), "Bottom friction beneath random waves", Coast. Eng., 24(3), 259-273. https://doi.org/10.1016/0378-3839(94)00023-Q
  11. Myrhaug, D. and Holmedal, L.E. (2002), "Bottom friction in nonlinear random waves plus current flow", Proceedings of the 28th Int. Conf. Coastal Eng., ASCE, Cardiff, Wales.
  12. Myrhaug, D. and Ong, M.C. (2009a), "Random wave-induced scour at the trunk section of a breakwater", Coast. Eng., 56(5-6), 688-692. https://doi.org/10.1016/j.coastaleng.2009.01.003
  13. Myrhaug, D. and Ong, M.C. (2009b), "Burial and scour of short cylinders under combined random waves and currents including effects of second order wave asymmetry", Coast. Eng., 56(1), 73-81. https://doi.org/10.1016/j.coastaleng.2008.07.006
  14. Myrhaug, D. and Ong, M.C. (2010), "Random wave-induced onshore scour characteristics around submerged breakwaters using a stochastic method", Ocean Eng., 37(13), 1233-1238. https://doi.org/10.1016/j.oceaneng.2010.04.008
  15. Myrhaug, D. and Ong, M.C. (2011a), "Long- and short-crested random wave-induced scour below pipelines", Proceedings of the Institution of Civil Engineers : Maritime Engineering, 164(4), 173-184.
  16. Myrhaug, D. and Ong, M.C. (2011b), Random wave-induced scour around marine structures using a stochastic method. I: Marine Technology and Engineering : CENTEC Anniversary Book, CRC Press.
  17. Myrhaug, D. and Ong, M.C. (2013a), "Scour around vertical pile foundations for offshore wind turbines due to long-crested and short-crested nonlinear random waves", J. Offshore Mech. Arctic Eng., 135(1), 011103. https://doi.org/10.1115/1.4007048
  18. Myrhaug, D. and Ong, M.C. (2013b), "Effects of sand-clay mixtures on scour around vertical piles due to long-crested and short-crested nonlinear random waves", J. Offshore Mech. Arctic Eng., 135(3), 034502. https://doi.org/10.1115/1.4023801
  19. Myrhaug, D. and Rue, H. (2003), "Scour below pipelines and around vertical piles in random waves", Coast. Eng., 48(4), 227-242. https://doi.org/10.1016/S0378-3839(03)00029-2
  20. Myrhaug, D. and Rue, H. (2005), "Scour around groups of slender vertical piles in random waves", Appl. Ocean Res., 27(1), 56-63. https://doi.org/10.1016/j.apor.2005.06.001
  21. Myrhaug, D., Foien, H. And Rue, H. (2007), "Tentative engineering approach to scour around breakwaters in random waves", Appl. Ocean Res., 29, 80-85. https://doi.org/10.1016/j.apor.2007.04.001
  22. Myrhaug, D., Holmedal, L.E., Simons, R.R. and MacIver, R.D. (2001), "Bottom friction in random waves plus current flow", Coast. Eng., 43(2), 75-92. https://doi.org/10.1016/S0378-3839(01)00007-2
  23. Myrhaug, D., Ong, M.C. and Gjengedal, C. (2008), "Scour below marine pipelines in shoaling conditions for random waves", Coast. Eng., 55(12), 1219-1223. https://doi.org/10.1016/j.coastaleng.2008.03.006
  24. Myrhaug, D., Ong, M.C., Foien, H., Gjengedal, C. and Leira, B.J. (2009), "Scour below pipelines and around vertical piles due to second-order random waves plus a current", Ocean Eng., 36(8), 605-616. https://doi.org/10.1016/j.oceaneng.2009.02.007
  25. Myrhaug, D., Rue, H. and Torum, A. (2004), "Tentative engineering approach to scour around breakwaters in random waves", Coast. Eng., 51(10), 1051-1065. https://doi.org/10.1016/j.coastaleng.2004.07.022
  26. Nielsen, A.W., Sumer, B.M., Ebbe, S.S. and Fredsoe, J. (2012), "Experimental study on the scour around a monopole in breaking waves", J. Waterway Port Coastal and Ocean Eng., 138(6), 501-506. https://doi.org/10.1061/(ASCE)WW.1943-5460.0000148
  27. Ong, M.C., Myrhaug, D. and Hesten, P. (2013), "Scour around vertical piles due to long-crested and short-crested nonlinear random waves plus a current", Coast. Eng., 73, 106-114. https://doi.org/10.1016/j.coastaleng.2012.10.005
  28. Soulsby, R.L. (1997), Dynamics of Marine Sands. A Manual for Practical Applications. Thomas Telford, London, UK.
  29. Sumer, B.M, Christiansen, N. and Fredsoe, J. (1992a), "Time scale of scour around a vertical pile", Proceedings of the 2nd Int. Offshore and Polar Eng. Conf., San Francisco, ISOPE, Golden CO, USA.
  30. Sumer, B.M. and Fredsoe, J. (1996), "Scour below pipelines in combined waves and current", Proceedings of the 15th OMAE Conf., Florence, Italy, ASME, New York.
  31. Sumer, B.M. and Fredsoe, J. (1998), "Wave scour around group of vertical piles", J. Waterway Port Coastal Ocean Eng., 124(5), 248-255. https://doi.org/10.1061/(ASCE)0733-950X(1998)124:5(248)
  32. Sumer, B.M. and Fredsoe, J. (2001), "Scour around pile in combined waves and current", J. Hydraulic Eng., 127(5), 403-411. https://doi.org/10.1061/(ASCE)0733-9429(2001)127:5(403)
  33. Sumer, B.M. and Fredsoe, J. (2002), The Mechanics of Scour in the Marine Environment, World Scientific, Singapore.
  34. Sumer, B.M., Christiansen, N. and Fredsoe, J. (1993), "Influence of cross-section on wave scour around piles", J. Waterway Port Coastal and Ocean Eng., 119(5), 477-495. https://doi.org/10.1061/(ASCE)0733-950X(1993)119:5(477)
  35. Sumer, B.M., Fredsoe, J. and Christiansen, N. (1992b), "Scour around vertical pile in waves", J. Waterway Port Coastal and Ocean Eng., 114(5), 599-614.
  36. Sumer, B.M., Fredsoe, J., Lamberti, A., Zanuttigh, B., Dixen, M., Gislason, K. and Di Penta, A.F. (2005), "Local scour at roundhead and along the trunk of low crested structures", Coast. Eng., 52(10-11), 995-1025. https://doi.org/10.1016/j.coastaleng.2005.09.012
  37. Testik, F.Y., Voropayev, S.I., Fernando, H.J.S. and Balasubramanian, S. (2007), "Mine burial in the shoaling zone: Scaling of laboratory results to oceanic situations", IEEE. J. Oceanic Eng., 32(1), 204-213. https://doi.org/10.1109/JOE.2007.890970
  38. Whitehouse, R.J.S. (1998), Scour at Marine Structures. A Manual for Practical Applications. Thomas Telford, London, UK.
  39. Young, I.R. (1999), Wind Generated Ocean Waves, Elsevier, Amsterdam.