Abstract: The influence of rock fragmentation on the trajectory of rolling rock on slopes is investigated using energy tracking method (ETM). Based on the impulse method, the ETM develops a multiple point energy conservation algorithm to improve the calculation accuracy. Compared with the traditional penalty function method, the advantage of the impulse method is that the ETM does not rely on penalty parameters, thus it improves the accuracy of simulation; ETM is a coupling algorithm of analytical solutions and numerical solutions, which improves the computational speed. Compared with traditional impulse methods, such as sequential impulse method and simultaneous impulse method, ETM can track the energy transfer between multiple blocks and multiple collision points during the collision process. Therefore, it can accurately simulate the high frequency collisions among hundreds and thousands of collision bodies. Failure pattern recognition simulation based on Weibull distribution is used to simulate the fragmentation of the rolling rock during the falling process. The results indicate that: (1) ETM is able to accurately simulate the three-dimensional trajectory of rolling rock on slopes; (2) when considering the rock fragmentation effect, the trajectory of the rolling stone fragments changes significantly compared to that of not considering the fragmentation of the rolling rocks. In this case, the horizontal lateral displacement increases obviously, so the slope protection scope needs to be enlarged horizontally. The effectiveness of the ETM and pattern recognition simulation in simulating falling rocks are verified in this paper, which is able to provide modelling tools for avoiding falling rock disasters.

Key words: energy tracking method(EMT), rockfall, rock fragmentation, pattern recognition simulation, slope protection