Abstract:Rockfall is one of the main geological disasters in mountainous areas,and the range of its distribution is very wide.It always occurs suddenly and hard to be forecasted, which can damage structures,obstruct transportation,threaten human lives and cause other serious consequences.The design of protective structure is based on the analysis of rockfall trajectories.However,the researches about the rockfall are limited,resulting in poor prevention treatments of rockfall.Based on a variety researches of rockfall cases the three-dimensional discontinuous deformation analysis(3-D DDA)was used to study the rockfall prevention subject.Compared with the two-dimensional model,the three dimensional model can take 3-D terrain into consideration,and analyze divergence angle.Rockfall on a rock slope was analyzed using 3-D DDA for countermeasures.The movement characteristics were investigated by numerical analysis with consideration of collisions between rockfall blocks.The results showed that wether to consider the collisions between rockfall blocks would cause a huge difference,and the collisions among falling rocks would usually cause the total energy loss, but some blocks would obtain the kinetic energy through collisions and move a longer distance.The interactions among falling rocks couldn’t be ignored.Compared with the existing methods,3-D DDA could directly simulate the collisions among the rocks,which was correspond to multi-blocks rockfall events. Effect of protective measure was verified by the movement characteristics.This method can be used to predict the multi-blocks rockfall movement characteristics on rock slopes,and offer a reference for planning and designing rockfall countermeasures.