A new evaluation index of rockburst tendency considering tunnel excavation and fracture distribution

Rockburst risk and tendency analysis of fractured rock mass after excavation and unloading has been gaining importance. Within the framework of a constitutive model based on internal variable thermodynamics, the energy dissipation rate is proposed as a new evaluation index of rockburst tendency. Taking the numerical simulation of a traffic tunnel in western China as an example to carry out the rockburst tendency analysis, the models with parallel fractures of different dip angles were established in FLAC^3D by Monte-Carlo method and MATLAB programming. Combined with the estimated in-situ stress of the deep-buried tunnel and the inversion results of constitutive parameters of rock mass, the influence of fracture dip angles on rockburst tendency of the surrounding rock is analyzed. The analysis results under different calculation conditions show that with the increase of fracture dip angle, the possible location of rockburst gradually transfers from the vault to the left arch waist. In addition, the comparison with the stress index verifies that the energy dissipation rate index can effectively evaluate the potential dangerous areas and rockburst positions after excavation and unloading of fractured rock mass, which has a reference value for the rockburst risk assessment in deep-buried tunnels.