Field experimental verifications of 3D DDA and its applications to kinematic evolutions of rockfalls

As a frequent occurring geomorphological process characterized by high energy and mobility, the rockfall movement is the basis of the disaster prediction and mitigation. In this study, the kinematic evolution behaviors of rockfalls are investigated using three-dimensional discontinuous deformation analysis (3D DDA) based on block kinematics. A series of field experiments are designed by orthogonal experimental method to study the block movement considering the influence of the slope angle, the characteristics of the block itself and the initial falling conditions. Selecting the combination of factors that have the most significant influence on the block movement, the 3D DDA numerical model is established and the effectiveness of 3D DDA is verified by comparing the displacement and kinetic energy evolutions obtained by experiments. Then, the 3D DDA is applied to simulate the rockfalls of Wangxia slope in Chongqing, and the kinematic evolutions of the entire rockfall processes are further studied by analyzing the rock mass instability and the movement trajectory and kinetic energy evolutions of blocks. The experimental results show that slope angle has the greatest influence on block kinematics, followed by block mass, falling height, block shape and falling angle. In the practical slope analysis, the rockfall processes consist of sliding failure, oblique projectile movement, flying over or colliding with the highway, and flying away from the slope, showing 3D movement characteristics due to lateral translation and rotation. The rockfall kinematic evolutions induce slope disasters to the highway, and pose a threat to shipping in Yangtze River channel. The 3D DDA method can quantitatively analyze the failure of dangerous rock masses and the kinematic evolutions of rockfalls after instability, which is helpful to provide revealing insights into the rockfall disaster processes and mechanisms.