Assessment of Rockfall Impact Force by Particle Flow Code Numerical Simulation Based on Discrete Element Model

To make a reasonable and effective assessment of rockfall impact force, a study on the impact force of falling down rockfall to a structure was carried out by using the method of PFC(particle flow code) based on the theory of DEM(discrete element model). The effects of rockfall height and gravity,and backfill soil thickness on the impact force were analyzed. The results of PFC numerical simulation were compared with those reached by other kinds of calculation methods. The results show that there is an obvious linear relationship between the impact force and the rockfall height or gravity. The linear variation range of the impact force with the changing of the rockfall height relates to the rockfall gravity, while the linear variation range of the impact force with the changing of the rockfall gravity relates to the backfill soil thickness. The impact force reduces by 50%-60% when the backfill soil thickness is 0.6 meter compared with no backfill soil. it tends to be stable when the backfill soil thickness is more than 2 meters, showing that there is a reasonable range of the backfill soil thickness. The total load of structure will increase if the backfill soil thickness exceeds the range. The method of PFC numerical simulation can simulate the effect of air acting on rockfall by setting damping coefficient, which makes the assessment of bigger size rockfall impact force more reasonable.