Mechanical and microstructural responses of yellow sandstone with prefabricated fissures to tailings water immersion
摘要
To elucidate the degradation mechanism of fissured sandstone under the immersion of tailings water, uniaxial compression tests and acoustic emission monitoring were conducted on samples soaked in tailings water and distilled water for different durations. Additionally, low-field nuclear magnetic resonance (NMR) technology was employed to investigate changes in their pore structures. The results indicate that the uniaxial compressive strength and elastic modulus of sandstone decrease exponentially with prolonged immersion time, with the chemical components in tailings water accelerating the degradation process. During immersion, the failure mode of sandstone gradually transitions from tensile failure to a mixed tensile-shear failure. Concurrently, the acoustic emission ring-down count and the proportion of events in the active phase decrease, while the proportion of events in the burst phase increases. Significant changes occur in the pore structure of sandstone after immersion, with the T2 spectrum shifting from a bimodal to a trimodal distribution. The proportion of micropores decreases, mesopores increases, and macropores remains basically unchanged. The increase in porosity is less pronounced in samples soaked in tailings water compared to those in distilled water. NMR imaging reveals that pores develop from the exterior towards the interior of the rock, and prefabricated fissures accelerate this process. These findings enhance our understanding of long-term water-induced weakening mechanisms, aiming to provide scientific references for optimizing the operational strategies and updating the design concepts of tailings dams.