Dynamic numerical simulation analysis of rockburst grade evaluation based on rock mass strength

The occurrence of rockbursts is closely related to the stress environment and structural characteristics of rock mass. The Lalin Railway Tunnel in China was taken as a case study, a modified method for evaluating rockburst grades was proposed based on the ratio of rock mass strength to maximum tangential stress at the tunnel wall, and the accuracy of this method was also validated. Furthermore, a three-dimensional numerical model of tunnel excavation was established using FLAC^3D (three-dimensional fast lagrangian analysis of continua). The rockburst grade of different locations (vault, arch waist and arch bottom) of the tunnel was then evaluated by using the modified method of rockburst grade evaluation. It shows that the modified method of rockburst grade evaluation has relatively high accuracy, and the evaluated results are in good agreement with the actual rockburst grades; The ratio of rock mass strength to maximum tangential stress of tunnel wall is greater than 0.0905, 0.0892 ~ 0.0905, 0.0300 ~ 0.0892, 0.0500 ~ 0.0300 and less than 0.0500 for no, slight, medium, strong and violent rockburst, respectively; when the distance between the monitoring section and the tunnel working face is less than 20 m, the surrounding rock is obviously affected by tunnel excavation activities and the risk of rockburst is relatively large; for tunnels with horizontal structural stress, the risk of rockburst in the surrounding rock of the arch is often higher than that of the waist and bottom of the arch. The results presented herein may provide reference for the evaluation of rockburst grade and the formulation of prevention and control measures.