This paper investigates a debris flow impulsive load on open sabo dam already observed in preliminary experiments. In the experiments, the debris flow impulsive load was reduced 20 % by the energy dissipator. Moreover, the DEM is utilized for a numerical simulation to elucidate the load reduction mechanism of the experiment. Herein, the numerical results reproduced the load-time relation and sedimentary process of the experimental results. The load reduction mechanism by the energy dissipator, is analyzed by tracing the movement of elements around ‘Dead Zone' and/or area of colliding with facilities. Lastly, it's pointed out that collision of the ‘dead zone' formed by the energy dissipator reduces velocity of the flowing elements, then impact load between the structure and those elements is reduced.
