Meso-structural evolution of sandstone under uniaxial loading: A study on microdefect compaction and transgranular crack formation mechanisms

Rock deterioration under uniaxial compression is significantly influenced by changes in meso-structure, which plays a key role in determining the mechanical behavior and stability of rock materials. Understanding how different loading stresses affect the evolution of meso-structure is crucial for assessing rock stability in engineering applications, such as tunneling and landslide prevention. This study investigates the damage mechanisms and meso-structural evolution of sandstone subjected to uniaxial compression at different loading stresses (0, 5, 15, 30, and 40 MPa). Utilizing Nuclear Magnetic Resonance (NMR), Scanning Electron Microscopy (SEM) and quantitative statistical analysis (e.g., Single-factor analysis of variance (ANOVA), Pearson correlation coefficients), the study analyzes how different stress levels influence the internal structural changes within the sandstone. The results revel that low loading stresses (5 and 15 MPa) primarily induce microdefect compaction and limited intergranular crack propagation, causing notable changes in failure strain without significant structural damage. In contrast, higher loading stresses (30 and 40 MPa) induce the formation of transgranular cracks, drastically reducing both failure strength and overall structural integrity. Meso-mechanical analysis identifies mineral rotation and crack propagation as critical factors driving these structural transformations. These findings demonstrate that rock deterioration is stress-dependent, with distinct characteristics at low versus high loading conditions. This research enhances the understanding of the underlying mechanisms of rock deterioration, providing valuable insights into rock stability evaluation. The findings are essential for predicting and mitigating geological hazards, offering critical implications for engineering practices aimed at enhancing rock stability and preventing disasters.