Wave Runup and Reflection at Rubble Mound Breakwaters with BPPT-Lock Armor Layer

Breakwaters play a crucial role in protecting coastlines, ports, and harbors from the impact of oceanic waves, ensuring safe navigation and cargo handling while minimizing erosion risks. The design of breakwater rubble-mound armor units requires meticulous attention to stone dimensions and shape to maintain structural stability. Investigating wave-induced runup and transmission is paramount in coastal structure design, driving comprehensive research into the performance of various armor units to enhance protective measures. A recently introduced type of armor units, termed BPPT-lock, lacks comprehensive assessments regarding wave runup and reflection, highlighting a gap in existing research literature. Physical experiments in wave flumes investigated reflections and runup, considering variations in wave height, period, front slope, and layer thickness coefficient. The Momentum Flux parameter achieved a coefficient of determination (R²) of 0.6654, lower than the surf similarity approach’s R² of 0.7258. However, Momentum Flux outperformed surf similarity for waves with periods between 1.88 and 2.82 s, yielding an R² of 0.8657. Experiments on slope variations showed that the steepest structure had the highest runup, while the structure with the smallest layer coefficient exhibited the greatest runup overall. Higher wave steepness correlated with shorter runup distances. A pronounced frontal slope on the breakwater increased the reflection coefficient, while a gentler slope reduced it. The layer thickness coefficient affected reflection: more armor units with a thickness of k∆1.6 improved wave dissipation and lowered the reflection coefficient, with no significant difference between k∆1.11 and k∆1.3. In comparison with other armor units, BPPT-lock armor units demonstrated effective run-up performance, achieving a relative runup lower than crushed stones and other units in the range of ξ to 6.5, and a reflection coefficient lower than A-Jack but higher than Dolos and Cobs.