The present study features on the detail analysis of wave force and the stability of armor units of Rubble Mound Breakwater (RMB) through a numerical model. A two-dimensional numerical reshaping model of uniform sphere units' breakwater was developed to illustrate the phenomenon.

Calculation results show the time history of change of water surface, pressures, velocities, wave-induced forces, and the displacement of armor units. Significant relation between wave induced force distribution on the surface armor units and the surface elevations of wave at certain phase has been found. It is understood that the resultant forces during wave rundown are greater than during wave runup. The resultant forces are greater at the surface units located near the water surface. The model also shows the relation between the displacement area and water line oscillation on the slope. The effective area of dislodged armor units is found to be between the maximum runup and the maximum rundown. The maximum depth until where the effectice wave induced forces work onto the armor units is between 1.5 to 2 times of wave height. The influence of wave height on the wave induced force magnitude is not unique, but in combination with other factors, such as the slope angle. Under the same attacking wave characteristics, the steeper the slope of rubble mound breakwater, the higher the quantity of the dislodge armor units.