QUANTITATIVE PREDICTION OF ROCKBURST RISK IN SEJILA TUNEL OF ONE RAILWAY

Rockburst is one of the main risks in the process of underground tunnel construction in high geostress area, which is characterized by sudden occurrence and high harmfulness. The quantitative prediction of rockburst damage degree is of great guiding significance to the design and construction of underground engineering in high in-situ stress area. By collecting a large number of characteristic parameters of typical rockburst tunnels at home and abroad and conducting statistical analysis, this paper establishes a quantitative rockburst risk prediction model that can predict the maximum depth of rockburst pit. At the same time, combined with the laboratory test, rock strength damage criterion and multiple linear regression inversion method for geostress field, the rockburst risk of Sejila Tunnel of one railway is quantitatively predicted, and the rockburst risk is compared and analyzed with similar engineering cases of Bayu tunnel in China. The conclusions are as follows: (1)The rockburst prediction model based on the linear statistical relationship between the depth of rockburst tunnel and the stress intensity ratio can realize the quantitative prediction and evaluation of rockburst risk. (2)The geostress field of Sejila Tunnel is obviously controlled by tectonic action, and the geostress along the whole line is generally high. In addition, the hard rock section along the tunnel accounts for a large proportion and the rockburst tendency is high, so the rockburst risk of high geostress is prominent. (3)It is predicted that the rock burst risk section of medium grade or above in Sejila Tunnel can reach 12 188 m, accounting for 32.1% of the total length of the tunnel. The rock burst will mainly occur in the section of weakly weathered granite, diorite and gneiss with large burial depth. (4)The predicted maximum pit depth of Sejila Tunnel is 3.42 m, which is less than the measured maximum pit depth(3.5 m) of the already connected Bayu tunnel. Under reasonable construction and prevention and control measures, the rock burst risk of Sejila Tunnel is generally controllable.