Abstract: To explore the influence of tunnel axis stress on rockburst, rockburst model tests were performed to reproduce the rockburst process of the tunnel. Under different intermediate principal stress conditions, the tests were carried out on cubic granite specimens with prefabricated holes by using the true triaxial rockburst test system. The whole rockburst process was monitored by a real-time video observation system and an acoustic emission system under true triaxial loading conditions. The test results show that no macroscopic damage, particle ejection, rock fracturing and block ejection are the four main stages of the whole rockburst process. The higher the intermediate principal stress is, the shorter the time between the ejection of the particles and the block injection is, the longer the splitting duration is, the shorter the ejection duration but more severe is. With a higher intermediate principal stress, the splitting failure is more obvious under the Poisson effect resulting from the tangential first principal stress and the axial intermediate principal stress. Besides, a higher stress level is required for rockburst, and the risk of rockburst in the tunnel is reduced. However, once the stress concentration level is high enough to induce rockburst, the rockburst intensity is higher.

Key words: tunnel, rockburst, model test, intermediate principal stress