土石流等天然災害可以被認定為顆粒流，為了解在土石流中，巨大顆粒與顆粒流整體的差異，本研究以PFC3d數值模式模擬，渠道中不同位置障礙物受到顆粒流撞擊的情況，並加入三個位置不同之大顆粒，比較共計八組模擬中的各項參數變化，並透過實驗與模擬的輪廓比較驗證模擬是否精確。
在障礙物所受的衝擊力中可以發現，在加入大顆粒之後，對於不同位置的障礙物的衝擊力最大值，並非全部上升。反而在大顆粒被抬升至顆粒流表面之後，顆粒流對位障礙物位在較下游情況下的衝擊力峰值較未加入大顆粒前低。同時我們也比較了不同位置的障礙物對於阻擋顆粒流流動的效果。

The movements of debris flows, landslides and debris avalanches can be regarded as granular flows. In order to understand the effect of the large particles in the debris flow, this study uses PFC3D to simulate the impact force upon the obstacles located at different locations in the channel by allocating three large particles in the source area prior to the mass movement. The results of numerical simulation were verified by the flume experiment with good agreement. The impact force of large particles upon obstacles depends on the location of the obstacles. We also compare the blocking effect of the obstacles at different locations.

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