A series of model experiments have been carried out for a caisson covered with wave dissipating blocks. The characteristics of random wave forces and the force
due to blocks on the upright section and the stability of the caisson against sliding are investigated.
　Wave pressure reduction by the blocks depends on the wave height and the width of covering blocks. Wave pressure reduce greatly for large waves, but the reduction is not significant for small waves.
　The static block force on the upright section depends on the height of piled blocks and the degree of compaction of blocks. During wave action, the block force
become smaller than the static block force because of increasing buoyancy and the rotational and horizontal movement of caisson.
　For usual design conditions the caisson stability against sliding can be judged without considering the block forces.