Landslide-debris avalanches always cause disastrous catastrophes because their high speed and long runout. Their complex movement mechanisms make the prediction of runout very difficult. Laboratory experiments are used to investigate some factors influencing the movement of rock fragments

including size of fragments

bed roughness and scrap. Flume tests show that the runout of rock fragments is decided by front part and increased with the increasing size of rock fragments. The runout becomes smaller when the bed roughness increasing or scrap is added. The movement mechanism of landslide-debris avalanche is also discussed based the physical properties of granular material and previous studies: the force between particles is much smaller than intact rock in high speed

so the “cohesion” of particles can not ensure the landslide maintain an fixed shape

and the friction reduces when transferred by the particles at bottom

making the result of long run out.