Effect Comparison of Environmental and Structural Parameters Affecting on Deformation and Hydraulic Stability of Reshaping Berm Breakwaters

Abstract

Berm breakwaters are reshaping rubble mound breakwaters, which as a result of impact with wave attacks, the seaside profile of these breakwaters reach a stable condition after erosion and reshaping. Berm recession (Rec) is one of the most important parameters that should be controlled for designing a stable berm breakwater. Failure of a berm breakwater is typically defined when the berm recession exceeds the initial berm width. Based on experimental tests, the effect of sea state and structural parameters on berm recession was investigated in this study. The berm recession was recorded under different number of waves through performing 34 experiments. The results showed that a berm breakwater experiences more than appproximately 90% of its final recession during exposing to the first 3000 waves. In addition, rising the berm elevation had less effect on reducing the berm recession in comparison with both increasing the berm width and decreasing the water depth. On the other hand, increasing the berm width was the most effective parameter in controlling the berm recession. So that, 20% increase in the berm width had a greater effect on decreasing the berm recession, than 45% increase in the berm elevation. By the way, especially in the absence of suitable stone materials, increasing the berm elevation can be yet a good alternative in order to design a stable structure with simple construction activities.

Keywords

• berm breakwaters
• berm elevation
• berm recession
• berm width
• stability