Abstract: The long-runout distance of rock avalanches is the largest accumulation range that sediment can reach, which has great significance in disaster warning and risk assessment. This paper describes a calculation model to predict the long-runout distance, which is of interest in connection with the motion of landslide and mass movement. By summarizing the research results of long-runout distance of rock avalanches and basing on dimensional analysis, it is considered that the potential energy of rock mass plays an important role on long-runout, and that the long-runout distance (L) is the function of potential energy. Then, experiments were performed with 4 different quartz granular materials, and masses of these granular materials with various initial volumes were released from rest in a chute. The front position of avalanches was recorded. The effect of mass volume(V), the slope angle of transport zone(?), fragments particle size(d) and maximum vertical travel distance(H) on the long-runout distance(L) were studied. The calculation model for long-runout distance on potential energy was established by stepwise regression method. The data of 38 landslide-avalanches triggered by the Wenchuan earthquake and other 17 typical landslide rock avalanches that are widely used internationally were taken to verify the calculation model. The results show that the transport distance calculation model established by potential energy of rock mass is reliable and that the transport distance calculation model is suitable for rock avalanche disaster warning and risk assessment in mountainous areas.

Key words: rock avalanche, long runout distance, calculation model, chute experiment, granular flow, stepwise regression