In this paper the wave force damping effects due to the deformed artificial blocks are discussed through the model experiments.
　Up to now there have been no unificative understandings as to the wave force damping effects of the artificial blocks, so that it has been an usual method to take the wave force damping coe fficient from the results of simple model tests or from the experiences in the field. As for this point, someunderstaings have been derived from the several model experiments in the breakwater laboratory. That is, the effects of the wave force damping of the deformed artificial blocks are recognized in the case in which the breaking wave acts on the vertical wall, but on the other hand the vertical wall is exposed to the severe attack of waves in the case of standing wave because the mound of the deformed blocks will help the wave breaking.
　All discussions about the wave force have been made by using the peak point in the measuring record of the wave force, and there have been remained many problems as for this point. Namely, it is very ambiguous whether or not the peak value of the wave force in the measuring record can be connected with the sliding or the overturning of the breakwater. It is said that the initial shock breaking wave pressure has the pressure head which is 5 or 6 times through 100 times of the deep water wave height. But the value of the shock pressure is strongly related with the responsibility of measuring apparatus. So it may be expected that, if we use the new apparatus being able to record the large frequency number compared with the old apparatus, there are some possibilities to get the large initial shock wave pressure in the new apparatus.
　In this reserch, in order to get rid of such a confused problem which lay in the experiments measuring the wave force by wave force meter, we have discussed the
waveforce acting on the vertical wall by using the newwave force measureing equipment that was developed in the breakwater laboratory.
　From the experiments, we got the several usuful conclusions.
(1) In order to diminish the wave force acting on the vertical wall, it is necessary to accord the crown height of the wave absorbor and that of the breakwater, and the wave absorbor width at the still water level has to be equal to 4 layer width of the deformed blocks.
(2) The wave force acting on the verical wall is expressed as follows if the wave absorbor is constructed in the manner as was metioned in (1).
　　　p=1.0ωH1/3
where, p; wave pressure acting on unit ara of the vertical wall (t/m2), ω; unit weight of the water (t/m3), H1/3; signifcant wave height at the deposition point of the breakwater(m).