The effects of rockfall volume on runout distance

The main goal of this paper is to clarify the effects of rockfall volume on its fluidization. For this purpose, outdoor rockfall experiments were carr ied out to analyze runout distances and individual movements of rockfall bl ocks and numerical simulations were conducted for these experiments to lear n more about the mechanism of rockfall fluidization. The rockfall experimen ts were conducted using an artificial slope on which granite slabs were sur faced and overlaid with cubiformed granite blocks. The size and number of b locks were varied in this series of experiments. Further, numerical simulat ions were carried out in which the coordinates of individual rockfall block s were traced in three-dimensional space from rockfall initiation to final deposition. It became clear from the experiments and simulations that the r unout distance had a positive correlation with the rockfall volume (number of rockfall blocks) and the runout distance of the gravity center of deposi ted rockfall mass had a negative correlation with the rockfall volume. To c larify the mechanism of these two phenomena, the positions of individual bl ocks from initial arrangements to final depositions were traced in the expe rimental and numerical simulations. This revealed that the relative positio ns of each block along the slope direction were not changed during rockfall movement. The reason for the block-sequence preservation was that front fa cing blocks in the initial cube arrangement accelerated and rear facing blo cks decelerated along the slope by internal collision between blocks. Furth er, as the rockfall volume increased, the opportunities for impact among th e rockfall blocks increased with the front facing blocks pushed farther. Wh ereas the gravity-center of the deposited rockfall mass had an inclination to travel shorter distances as rockfall blocks increased according to the i ncrease of kinetic energy dispersed by the collision of blocks. (C) 2000 El sevier Science B.V. All rights reserved.