The columnar dangerous rock mass is well developed in the Three Gorges Reservoir area. The change of water level accelerates the deterioration of the pedestal rock mass of the columnar dangerous rock mass and increases the risk of its crushing failure collapse. The potential surge disaster threatens the safety of shipping. According to the survey data of relevant dangerous rock masses in the Three Gorges Reservoir area

a dynamic observation system and experiment platform for particle column collapse was constructed

and physical model experiments on granular column collapse surge were carried out. The experiment results show that the crushing failure mode of dangerous rock mass is similar to that of the composite movement of collapsing-sliding of the experimental granular column. The staged motion of the granular column can be analyzed by the velocity of gravity center

which can represent the velocity of the particles. Formulas are derived by the nonlinear regression to estimate the water entry velocity of the particle and the maximum amplitude of surge. The Froude number is the main sensitive factor of the formula. Compared with the prediction formula of rigid block subsidence

the experimental formula in this paper is more suitable for crushing failure mode and has higher prediction accuracy. This research will provide the technical support for the prediction of the surge caused by the instability of the columnar dangerous rock mass in the reservoir area.