A STUDY ON MOTION CHARACTERISTICS OF ROCKFALL UNDER SEISMIC LOADINGS BY DDA

In order to research the failure of rock mass induced by earthquakes, we took the rock avalanche at Heyezhai, Sichuan, China as the research object. Firstly, we simulated the failure under self-weight by DDA and RocFall codes. The results show RocFall and DDA could coincide with each other well. Then we simulated the failure of the single rock under seismic loading with the influence of density, height, size and peak acceleration of horizontal simple harmonic waves. Finally, we simulated the failure of the rock with a set of parallel joints. In the simulation, we monitored some important parameters such as trajectories, horizontal displacement, velocity and the maximum bounce height at the slope foot. The simulation results show the follows. (1)The natural slope angle of rock zone 2 is at 65°~75°, the rockfall accelerated on the slope surface and then ejected at the height of about 132 m. The main motion modes are rolling, collision and bouncing. (2)The breakthrough time of weak structural plane decreases with increasing of the density, volume and peak acceleration of seismic waves. (3)The peak velocity increases with increasing of slope height, volume and peak acceleration of seismic waves. (4)The horizontal displacement increases with increasing of the density, slope height and peak acceleration of seismic waves. (5)The maximum jumping height of rockfall at the foot of slope is positively correlated with various factors. We continued to study the failure of rock mass with internal joints under seismic loading: (1)The horizontal displacement range of rockfall is 191.5~243.8 m. (2)The maximum bounce height at the slope foot was 13.8 m.