Study on Effects of Mineral and Pore Characteristics on Mechanical Behavior and Acoustic Emission of Sandstone

This study conducts acoustic emission (AE) tests on five types of medium-grained sandstones under uniaxial compression coupled with analysis using nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) techniques. We systematically investigated the relationship among mineral content, pore structure (porosity and pore type), mechanical properties, damage mechanisms, and AE characteristics. The results show that the uniaxial compressive strength (UCS) and modulus of elasticity (E) of sandstones are positively correlated with the content of feldspar and other minerals, while exhibiting an inverse relationship with quartz content. Simultaneously, they are negatively correlated with the porosity and influenced by the percentage of mesopores. The AE energy and cumulative AE energy characteristics are jointly influenced by the pore structure and fracture mechanism. The correspondence between SEM fracture morphological features and the change rule of fractal dimension (D) was established based on fractal theory. Additionally, the crack classification results based on the ratio of rise time to amplitude (RA) and average frequency (AF) align with the macroscopic failure mode. However, the cumulative number of cracks and their corresponding cumulative AE energy are jointly influenced by both the pore structure and the fracture mechanism. The distribution characteristics of the AE dominant frequency are influenced by porosity and correlated with the complexity of internal fracture patterns. Furthermore, the "three-frequency synergistic growth phenomenon" occurs during macroscopic damage. The research findings provide a scientific basis for the assessment and monitoring of sandstone rock stability.