The invention relates to a risk-based tunnel supporting structure design method, comprising three links: determining the initial design scheme of a tunnel supporting structure, evaluating the risk of each supporting scheme, and making decision and analyzing the supporting schemes. In the method, a probability method and a risk analysis model are applied to carry out quantitative description to physical
mechanics indexes of a surrounding rock and the uncertainty in
geological exploration; the initial design scheme for supporting is given according to the level of the surrounding rock; space effect of tunnel excavation is considered and a convergence-confinement method is improved through the hardening process for pneumatically placed concrete supporting, the calculation procedures of the improved convergence-confinement method are used for analyzing the determined supporting design scheme, and the
failure probability of the supporting and the surrounding rock is given under different construction parameters; and then the
risk evaluation is carried out to the supporting design scheme,
accident risk acceptance criteria is determined, and proper supporting design scheme is determined by a
decision maker. In the method, the risk ideal is led in
engineering practice for
processing various uncertain problems in the tunnel structure design, so as to be beneficial to carrying out quantitative analysis and evaluation to the effect of the uncertain factors in the tunnel supporting structure design and ensure the safety and the investment control of the tunnel forcefully and comprehensively.