Abstract: With the main mechanisms of energy guiding and energy dissipation, the rockfall attenuator barrier has become a flexible structure to control rockfall disaster. The problems of difficult maintenance and high cost hinder the wide application of classic rockfall attenuator barriers in the field of rockfall protection. Therefore, combining with the lower open-ended design concept, we optimize the extension length and propose an improved rockfall attenuator barrier. In this study, the energy dissipation mechanism of the improved rockfall attenuator barrier under different extension lengths was investigated, by carrying out in-situ tests of the rockfall impact. The results show that the improved rockfall attenuator barrier is effective in cleaning up the rockfall stopped in the mesh. The constraint and friction effect of the improved rockfall attenuator barrier can effectively exert its flexible energy dissipation characteristics, thus reducing the impact energy of the rockfall. When the extension length of the improved rockfall attenuator barrier increases from 3 m to 7 m, the energy attenuation rate of the rockfall increases by approximately 20%. However, the increment of the energy attenuation rate gradually decreases with the increase of the extension length. To further improve the energy dissipation effect of the improved rockfall attenuator barrier, the influence of impact positions and angles of the rockfall on the energy dissipation effect of the improved rockfall attenuator barrier was studied by numerical simulation. The simulation results show that the energy attenuation rate was the highest when the rockfall impacted the middle position of the improved rockfall attenuator barrier, and the energy attenuation rate was increased by 20% compared with the position at the side of the impact edge. The energy attenuation rate of the rockfall reached the highest at 74.1%, when the angle between the impact direction of the rockfall and the improved rockfall attenuator barrier was approximately 45o. Therefore, the energy dissipation effect of the rockfall attenuator barrier can be maximized by reasonably setting extension length, installation location and inclination angle in engineering practice.

Key words: rockfall impacts, improved rockfall attenuator barrier, energy dissipation mechanism, in-situ test, numerical simulation