Study on the evolution of microscopic damage and mechanisms underlying mechanical deterioration of diorite under water action: Comparison of clay-containing and clay-free mineral fractions

The evolution of both macroscopic and microscopic damage in diorite under the influence of water action is critical for the design and stability assessment of related geological engineering projects. In particular, the strong interaction between clay minerals and water is a crucial factor contributing to the deterioration of the mechanical properties of diorite. However, the influence of clay minerals on the microstructure and the evolution of microscopic damage in diorite necessitates further investigation. In this study, we conducted uniaxial compression tests, open porosity tests, acoustic emission (AE) tests, digital image correlation (DIC), and scanning electron microscopy (SEM) tests on both clay-containing and clay-free diorite at varying levels of water saturation. We systematically investigated the macroscopic mechanical properties, microscopic damage and deformation evolution, as well as the microscopic pore structure characteristics of diorite across multiple scales. The results indicate that clay minerals significantly enhance the hydrophilicity of rocks, prolong the hydration duration, and accelerate the evolution of microscopic damage, as evidenced by the AE energy jump points, while reducing global strain anisotropy. Furthermore, it was observed that the porosity of rocks devoid of clay minerals increases logarithmically, with the water-rock interaction process primarily characterized by the dissolution of mineral grains. In contrast, the porosity of rocks containing clay minerals exhibits exponential growth, and the damage mechanism transitions from the dissolution of mineral grains and minor swelling of clay minerals to intense swelling as water saturation increases. This study elucidates the macro-meso-micro mechanical response behavior of diorite under hydration and highlights the pivotal role of clay minerals in this process. The findings enhance the understanding of diorite hydration processes, providing a theoretical basis for evaluating the geotechnical stability of diorite in groundwater-rich areas and for designing effective disaster prevention measures. • Comparison of damage evolution in clay-bearing and clay-free diorite under water. • A method for describing spatial distribution anisotropy of the deformation field. • Mesoscopic damage model of diorite clay-bearing and clay-free minerals under water. • Deterioration caused by combined effects of mineral dissolution and clay swelling.