Reliability-based design and sensitivity analysis of rock armors for rubble-mound breakwater

Predicting the stability of armor blocks placed on breakwaters is one of the main challenges in coastal and ocean engineering. However, the armor layer’s damage mechanism is very complicated so that there are many uncertainties in the estimation of different parameters in armor design. The inherent uncertainties in these parameters necessitate reliability analysis to ensure the stability of the breakwaters. This study proposed a reliability-based framework for estimating the rock armors weight based on the probabilistic analysis. The effect of different sources of uncertainties in determining effective parameters such as wave height, wave period, water-level changes and armor density was introduced and applied in calculating rock armors weight. Moreover, the correlations between breakwater life span, its probability of failure and stable armor weight were also considered in the analysis. Based on this method, armor weight could be computed according to any desired reliability level and breakwater life span. Results of sensitivity analysis showed that the most critical parameters affecting the reliability of armor weight are wave height and dimensionless damage level. Finally, the presented case study in this article addressed the use of this method in the design of armor weight for a breakwater constructed in the southern part of the Caspian Sea. Results showed that the stable armor weight to maintain a probability of failure equal to 0.005 placed on a breakwater with 50-year life span under a 100-year design storm condition in the Caspian Sea is about 24.28 ton. Moreover, by increasing the breakwater life span from 50 to 100 years, the armor weight increases only by about 10%.