On the stability of submerged rigid breakwaters against solitary waves

The stability of submerged rigid breakwaters subject to the action of solitary waves is here investigated by an experimental and numerical approach. Attention is paid to the features of the horizontal and vertical hydrodynamic forces which could make these marine structures unstable. The current work considers submerged barriers with square and rectangular sections and three different relative heights. Experimental tests were undertaken in a wave flume, adopting twelve pressure sensors along the external contour of the barriers in order to calculate the hydrodynamic loads. Numerical simulations were performed using the weaklycompressible delta-LES-SPH model. The aim of these simulations was to enlarge the laboratory cases in order to achieve potential critical conditions against sliding, overturning and bearing capacity of foundation. It was found that, by increasing the relative height of the breakwaters, the wave loads tended to grow, particularly for the horizontal ones. This aspect implied that the barrier with the highest relative height represents the most disadvantageous configuration for its stability. For the square barrier, the critical conditions against sliding and overturning appeared in correspondence of the highest wave amplitudes, while an effective area at the foundation/soil interface occurred starting from moderate wave amplitudes. Practical semi-empirical equations to determine the minimum safety factors as a function of wave amplitude, water depth, barrier geometry and materials were deduced.