Abstract: The collapse of dangerous rock mass is one of the key problems in the field of geological hazards. At present, most of them evaluate the stability of dangerous rock mass from the perspective of limit equilibrium and fracture mechanics. In this paper, considering the impact force of rockfall collision, an estimation method for the stability coefficient of dangerous rock mass under the rockfall impact is proposed, and the stability coefficient of toppling dangerous rock mass is evaluated by using the limit equilibrium method and numerical analysis. The results show that the trends obtained by theoretical estimation and numerical simulation analysis are consistent. The stability coefficients under natural, rainstorm and rockfall impact are 4.85, 1.21, 0.78 and 2.2, 1.11, 0.8 respectively; The rainstorm and rockfall impact have a great impact on the stability of dangerous rock mass. The stability coefficients obtained from theoretical analysis and numerical analysis under rainstorm conditions have decreased by 75% and 54% respectively compared with the natural conditions; The stability coefficient decreases by 84% and 65% respectively under the action of rainstorm and rockfall impact. The research results can provide reference for the stability evaluation of similar projects.

Key words: Falling Rocks, Collision, Toppling Dangerous Rock Mass, Impact Force, FLAC3D