Saturation effect on storage-dissipation properties and failure characteristics of red sandstone: Energy mechanism of water in preventing rockburst

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To investigate the effect of saturation on the storage-dissipation properties and failure characteristics of red sandstone, as well as the energy mechanism of rockburst prevention by water, a series of uniaxial compression and uniaxial loading–unloading tests were conducted under five saturation levels. The effect of saturation on the mechanical properties and elastic energy density was analyzed, and a method for obtaining peak energy density was proposed. The effect of saturation on the energy evolution was examined, and the energy mechanism of water in preventing rockburst was revealed. The results indicate that an increase in saturation of red sandstone decreases the input energy density, elastic energy density, dissipated energy density, peak strength and peak strain; the compaction phase of the stress–strain curve becomes shorter; the failure mode transitions from X-conjugate oblique shear to single oblique shear; the variation in the debris ejection trajectory is as follows: radiation → X-ray → oblique upward parabola → horizontal parabola → oblique downward parabola; the degree of failure intensity and fragmentation is decreased gradually. Elastic energy density is interconnected with both saturation and stress but independent of the loading path. Saturation exhibits a dual effect on the energy storage property, i.e., increasing saturation increases the energy storage efficiency and reduces the energy storage capacity. The ratio of peak elastic energy density to peak input energy density remains constant irrespective of saturation levels. Water prevents rockburst by decreasing the energy storage capacity of surrounding rock, alleviating the stress of surrounding rock to reduce energy storage, and elevating the energy release threshold of high-energy surrounding rock. The findings of this study contribute to understanding the effect of water on rock failure from an energy perspective, as well as provide theoretical guidance for rockburst prevention by water in deep tunnels.