Abstract: To further study the occurrence process and mechanism of rockburst induced by excavation of deep caverns, the true triaxial electro-hydraulic servo mutagenesis test system was used to carry out experimental research on granite with strong rockburst tendency and simulated the three-dimensional stress state at a depth of 500 meters. The excavation process near the cavern was simulated by unloading the unilateral load of the surrounding rock, and ultimately inducing rockbursts due to stress redistribution of the surrounding rock. In the experiment, monitoring equipment observed real-time tunnel wall failures. The test results revealed: (1) the rockburst process under single-side unloading can be divided into six stages - stress redistribution post-unloading, preparation period, initial cuttings ejection and spalling, calm period, secondary cuttings ejection and spalling, and severe damage; (2) Rockbursts in the cave wall exhibited distinct temporal and spatial characteristics and asymmetry under unloading influence, with cracks initially appearing at the cave roof's base post-unloading, followed by severe rockbursts on the side opposite the unloading surface, forming a V-shaped trough along the axis during subsequent loading; (3) The defined hysteresis effect coefficient indicated that compared to rockbursts under three-direction loading, single-side unloading-induced rockbursts displayed greater abruptness and were more prone to cavern collapse. To mitigate such rockbursts, support and reinforcement measures should be implemented on the existing cavern side opposite the unloading surface when excavating adjacent caverns.

Key words: experimental simulation, adjacent cavern excavation, rockburst, true triaxial test system, single-side unloading