Abstract:

Research on failure criterion and evolution process of deformation instability of tunnels has been one of the hot issues and difficulties in underground engineering field. Based on the synergetic theory and chaotic dynamics, different stages of tunnel excavation and nonlinear dynamics evolution characteristics for the whole process of deformation failure on surrounding rocks are presented. The whole process is divided into three stages as equilibrium stage, nonequilibrium-linear stage and nonequilibrium- nonlinear stage. The fluctuation correlation mechanism of the whole tunnel system is revealed by systematical analysis; and then the nonlinear dynamic evolution model is established. By combining the practice project with the length of time sequence for general deformation monitoring data as well as the effective analysis by chaotic dynamics, the dynamical criterion of the stability evolution process of the tunnel system is conducted separately under different data sequence lengths (more than 3 000 and less than 3 000). According to unstable and failure features of each evaluating stage of the tunnel system, the dynamic criterion is proposed. This criterion is employed to get a stability judgment of an overlapped tunnel in Guangzhou metro, of which reasonability and reliability are testified. This research has a great significance for the stability judgment of the surrounding rocks of tunnels.

Key words: tunnel, deformation instability, nonlinear dynamics, evolution model, failure criterion