Influence Of Rock-shape On Rockfall Movement Characteristics Under Earthquake

Rockfall is a common disaster in mountain areas,which causes serious consequences in terms of home destoryed and property lost throughout the world.Compared with other rockfall disasters,earthquake-induced rockfall can causes serious consequences because its strong movement and large scale.In addition,it is apparent that particular geological environments produce characteristic rock shape,and different rock shapes may produce different characteristic of rockfall movement.These aspects of rockfall are poorly understood.Therefore,in order to mitigate rockfall risk,it is important to estimate the movement characteristics of rockfall.In this paper,in order to explore the rock shape and earthquake on the characteristics of rockfall movement,the rock shape were characterized and reconstructed from two dimensional(2-D)and three dimensional(3-D),based on discontinuous deformation analysis(DDA)method,more than 7000 times of rockfall movement processes have been simulated.Based on the discrete Fourier transform(DFT)to study the shape characteristics of rockfall,the result show that:(1)Comparing the reconstructed rockfall by DFT and railway ballast for three levels of shape,it was found that the reconstructed rockfall can be used to represent the real rockfall.(2)The three kinds of Fourier descriptors has strong correlation with the three levels of shape,and the three kinds of Fourier descriptors are defined as the overall shape index(W-index),the concave-convexity index(P-index)and the roughness index(D-index)respectively.More than 7000 rockfall simulations by 2-D DDA and 3-D DDA,the results show that:(1)Four basic examples of DDA for rockfall simulation are designed,including free fall,rolling,sliding and collision rebound,it was found that the DDA method is suitable for the movement characteristics analysis of rockfall.(2)Both earthquake and non-earthquake conditions,the horizontal and lateral movement of rockfall are negatively correlated with three shape index.The influence of shape index of rockfall on its movement ability is as follows:the W index,the P index and the D index.(3)With the increase of seismic amplitude,the horizontal movement and lateral movement of rockfall will increase significantly,while the influence of frequency on rockfall movement is not obvious.The influence of rock shape on rockfall movement is even more than that of earthquake.(4)Compared with the 2-D DDA and3-D DDA rockfall simulation,the horizontal distance of the 2-D DDA simulation result is larger than the simulation result of 3-D DDA,and the rockfall jumping height of the 3-D DDA simulation is higher than 2-D DDA simulation.