Experimental study of 2D scour and its protection at a rubble-mound breakwater

Abstract This study deals with the 2D scour at the trunk section of a rubble-mound breakwater. Two breakwater models with slopes of 1:1.2 and 1:1.75 are employed for the experimental study of the scour in a wave flume. 2D scour at a vertical-wall breakwater was also included as a reference case. Tests were conducted with both regular waves and irregular waves. It was found that the scour/deposition pattern in front of the rubble-mound breakwater emerges in the form of alternating scour and deposition areas lying parallel to the breakwater, similar to the case of the vertical-wall breakwater. The maximum scour depth, however, was found to be smaller in the present case than that of the vertical-wall breakwater case. In the case of the irregular waves, the scour depth at the breakwater decreases with respect to that experienced in the case of the regular waves. Countermeasures for toe protection were also investigated for the following cases: (1) the protection apron with one layer of stones and (2) that with several layers of stones. The mechanism of slumping down of stones of the protection apron was also considered. The results of the toe protection study are given in the form of diagrams.

[1]  John B. Herbich,et al.  Handbook of coastal and ocean engineering , 1990 .

[2]  Jørgen Fredsøe,et al.  CROSS-FLOW VIBRATIONS OF CYLINDER IN IRREGULAR OSCILLATORY FLOW , 1994 .

[3]  Steven A Hughes,et al.  Scour Hole Problems Experienced by the Corps of Engineers; Data Presentation and Summary , 1993 .

[4]  Gert Klopman,et al.  Random Wave Measurements in Front of Reflective Structures , 1999 .

[5]  J. Richard Weggel.  Coastal Structures ’83 , 1983 .

[6]  Jørgen Fredsøe,et al.  Turbulent Boundary Layer in Wave‐current Motion , 1984 .

[7]  Toru Sawaragi,et al.  Scouring Due to Wave Action at the Toe of Permeable Coastal Structures , 1966 .

[8]  Isao Irie,et al.  LABORATORY REPRODUCTION OF SEABED SCOUR IN FRONT OF BREAKWATERS , 1984 .

[9]  Miguel A. Losada,et al.  Flow characteristics on rough, permeable slopes under wave action , 1980 .

[10]  J. Herbich,et al.  Scour of Sand Beaches in Front of Seawalls , 1968 .

[11]  Steven A. Hughes,et al.  Estimating Wave-Induced Kinematics at Sloping Structures , 1995 .

[12]  J. Eckert.  Design of Toe Protection for Coastal Structures , 1983 .

[13]  B. M. Sumer,et al.  Time Scale For Wave/Current Scour Below Pipelines , 1991 .

[14]  Jørgen Fredsøe,et al.  Scour at the round head of a rubble-mound breakwater , 1997 .

[15]  Steven A. Hughes,et al.  Wave-Induced Scour Prediction at Vertical Walls , 1991 .

[16]  Tom O'Donoghue,et al.  Wave phase shift at coastal structures , 1998 .

[17]  S. L. Xie,et al.  Scouring patterns in front of vertical breakwaters and their influences on the stability of the foundation of the breakwaters , 1981 .

[18]  Jørgen Fredsøe,et al.  Scour at the head of a vertical-wall breakwater , 1997 .

[19]  Chiang C. Mei,et al.  Mass Transport by Waves and Offshore Sand Bedforms , 1973 .

[20]  Jørgen Fredsøe,et al.  INFLUENCE OF CROSS SECTION ON WAVE SCOUR AROUND PILES , 1993 .

[21]  Iehisa Nezu,et al.  Turbulence in open-channel flows , 1993 .

[22]  R. Bagnold.  An approach to the sediment transport problem from general physics , 1966 .

[23]  Jimmy E. Fowler,et al.  Scour problems and methods for prediction of maximum scour at vertical seawalls , 1992 .

[24]  H. Oumeraci,et al.  Review and analysis of vertical breakwater failures — lessons learned , 1994 .

[25]  S Xie.  SCOURING PATTERNS IN FRONT OF VERTICAL BREAKWATERS , 1985 .