Failure characteristics and energy properties of red sandstone under uniaxial compression: water content effect and its application

To study the influence of water content (w) on the failure characteristics and energy properties of red sandstone, cylindrical specimens with varying w were prepared for uniaxial compression and single cyclic loading–unloading uniaxial compression tests. The effects of w on the mechanical properties, fractal dimension, failure intensity, energy properties, and acoustic emission (AE) of red sandstone were analyzed. The applicability of rockburst tendency indicators under different w conditions was examined, and the optimal w for preventing rockbursts was discussed. The findings indicate that water can weaken the strength and elasticity modulus of red sandstone. Water reduces the ultimate energy storage capacity while increasing energy storage efficiency. As the w increases, the fractal dimension of fragments, peak energy density, failure energy density, cumulative AE energy and count all decrease; the mean particle size increases, and these effects are significant at w ≤ 0.25w_s. The mean particle size decreases linearly with increasing peak elastic energy density. The rock fragmentation is primarily dependent on input energy; the more input energy, the more severe the rock fragmentation. The PES index can effectively characterize the rockburst proneness of red sandstone with different w. The optimal w to prevent rockburst is 0.25w_s achieved by injecting water for approximately 1.3 h. These results can provide theoretical guidance for the support design of caverns in water-bearing strata and disaster prevention in high-risk rockburst sections.