Abstract
Run-out distances of rockfall mass had been investigated on granitic rock blocks by means of a large-scale rockfall apparatus. Rockfall specimens had been prepared under dry and water-saturated conditions. Longitudinal run-out distances between gravity centres before experiments and at depositions were 10 % longer in water-saturated specimens than dry specimens when the specimens were with the same number of rock blocks in our rockfall experiments. Lateral expansions at deposition were larger in experiments with larger number of rock blocks. However, the standard deviations in lateral direction at deposition normalised by those at initial arrangements before experiments became smaller in experiments with larger number of blocks. Equivalent coefficients of friction between gravity centres were in positive correlation with number of rock blocks, which were contradicted to the fact of a negative correlation between landslide mass and equivalent coefficient friction in the classic studies on the landslide run-out distances. These were likely attributable to the facts that pore-structures were not formed in the rock-mass and no excess of pore-pressure was built-up during the downslope motion regardless of the rock-mass volume in our experiments, and rock blocks made inelastic collisions much more when the specimens consisted of larger number of rock blocks, in which much kinetic energy was consumed.
