Abstract:

The instability and failure of surrounding rock in water-bearing weak strata are often closely related to the effects of water. To deeply reveal the influence and mechanical mechanism of water saturation on rock damage and failure, uniaxial compression tests on white sandstone under dry and water-saturated conditions were carried out. Through comparative analysis, the effects and mechanisms of water saturation on strength, deformation, stress thresholds, strain energy, and acoustic emission characteristics were studied. The results showed the following when the white sandstone was water-saturated: (1) Uniaxial compressive strength and elastic modulus decrease, while Poisson’s ratio increases.(2) The normalized crack initiation stress (σ_ci/σ_f) decreases. The analysis shows that the softening effect of water weakens the bonding between mineral particles, making new cracks easier to initiate, thus leading to a decrease in σ_ci/σ_f.(3) The normalized crack damage stress (σ_cd/σ_f) decreases. Based on the analysis of the AE b-value, the proportion of small-scale ruptures increases. The increase in the proportion of small-scale fractures makes it easier for microcracks to coalesce into macrofractures, leading to a decrease in σ_cd/σ_f.(4) The total energy (U), elastic energy (U_e), and dissipated energy (U_d) at peak strength decrease, and the ratio of elastic energy to total energy (U_e/U) also decreases.(5) The analysis based on AE RA value (ratio of rise time to amplitude) and AF value (average frequency) shows that the proportion of shear fractures increases after water saturation, making it easier to produce intragranular fractures. The research results provide important insights into the failure mechanisms of water-saturated rocks.

Key words: white sandstone, water saturation, stress thresholds, energy evolution, damage failure, acoustic emission