• Water immersion significantly degrades the mechanical properties of rectangular tunnel specimens, with average peak stress decreasing by up to 34% after 62 days.
• Energy dissipation analysis reveals that water reduces both elastic and dissipated strain energy, weakening the rock's energy storage capacity.
• AE monitoring shows that water immersion drastically reduces cumulative AE parameters, indicating suppressed microcracking activity.
• The proposed energy damage model outperforms the AE damage model in fitting experimental data, enhancing rockburst prediction accuracy.