Abstract:
The coal body contains multi-scale primary cracks and filling minerals. The anisotropy of the spatial distribution of the two is significant, and the relative positional relationship is diverse, which affects the mechanical properties and mining dynamic behavior of the coal body. Based on CT scanning and digital core technology, the spatial distribution characteristics of fracture-mineral in coal samples were identified, and the typical combination scenes of typical fracture-mineral spatial distribution in coal samples were constructed. On this basis, the influence mechanism of different fracture-mineral spatial combination distribution modes on the mechanical behavior of coal was further revealed.The results indicate that:(1) Based on the limited sample analysis of this study, the fracture-mineral spatial fabric exhibits two typical spatial positional relationships: parallel and vertical.(2) The vertical spacing between fractures and minerals exerts a significant influence on the direction of fracture propagation, and there exists a Spacing Critical Value (SCV). When the spacing is less than the SCV, fracture propagation tends to approach the mineral boundary along the development direction of primary fractures. When the spacing exceeds the SCV, fracture propagation continues to extend further along the direction of primary fractures, and the mineral's control over the fracture propagation direction is weakened.(3) The presence of filled minerals alters the mechanical properties of the specimens (including uniaxial compressive strength, stress-strain behavior, and elastic modulus), and the degree of such alteration is still correlated with the SCV. When the spacing is less than the SCV, the uniaxial compressive strength of the specimens is positively correlated with the spacing, but all values are lower than that of coal without filled minerals. When the spacing is greater than the SCV, the uniaxial compressive strength of the specimens has no significant correlation with the spacing, but all values are higher than that of coal without filled minerals. On this basis, the judgment criteria for the four "modes" (Parallel Separation, Parallel Coplanar, Vertical Intersection, Vertical Separation) are further quantified according to the SCV.(4) The fracture-mineral spatial fabric mode dominates the mechanical properties and behavioral responses of coal. The "Parallel Coplanar" and "Vertical Intersection" modes weaken coal strength; compared with specimens without filled minerals, their uniaxial compressive strengths decrease by 8.42% and 8.96%, respectively. The "Parallel Separation" and "Vertical Separation" modes enhance coal strength; compared with specimens without filled minerals, their uniaxial compressive strengths increase by 7.17% and 10.42%, respectively.