Abstract: Herein, based on the statistical analysis results of collapse cases, the basic characteristics of tunnel collapse accidents are revealed to investigate the typical model and evolution law of tunnel collapse accidents. Then, the longitudinal curve of the virtual support force is obtained, and the relationship between the virtual support force and collapse accidents is determined according to the release characteristics of the virtual support force. Finally, the control requirements of collapse accidents are given. The following results are found: (1)Collapse accidents caused by surrounding rock failure, including excavation face failure collapse and closed collapse, account for a significant number of accidents (68%), deaths (53.7%), and human in risk (68%); the closed collapse accident has the largest number of human in risk in a single accident with the greatest potential harm. (2) The virtual support force of surrounding rock at the tunnel face decreases with decreasing cohesion of surrounding rock; the virtual support force of surrounding rock at two times the radius behind excavation face is mostly released (less than 5%〖WT５《TNR#I》〗pi〖WT５《TNR》〗). (3) In the second stage of deformation and virtual support force release, the surrounding rock deforms sharply, and the virtual support force is also rapidly released with a large release amount. Therefore, the second stage is the key step in controlling the tunnel collapse.

Key words: tunnel collapse, tunnel face failure, closed collapse, virtual support force, longitudinal distribution characteristics, control measures