Virtual Performance of Rubble Mound Structures

The previous numerical simulation of the performance of rubble mound structures under sequences of hurricanes is extended to compute the reduction of the minimum cover depth of the armor stone layer under sequences of storms. The computed cover depth is reduced episodically by several major storms but the reduction rate decreases as the damaged armor layer ages. The performance is compared for the two-layer thick armor layers with the high and low nominal stone diameters whose ratio is 1.5. The reduction and variability of the normalized cover depth is much smaller for the high nominal diameter D_n50. The quality of armor stone placement is less important than the difference between the high and low D_n50. To compare the performance of the high and low D_n50 for the same layer thickness, computation is also made for the performance of the three-layer thick armor layer with the low D_n50. The increase of the initial layer thickness for the low D_n50 does not reduce the damage and variability of the cover depth but increases the remaining capacity of the damaged armor layer for protecting the underlayer to the level of the two-layer thick armor layer with the high D_n50 if the three-layer thick stone layer is constructed well.