• Distinct influence of mineral content on damage mechanisms: Quartz primarily influences tensile damage, while feldspar governs shear damage. An unequal ratio between quartz and feldspar significantly increases crack complexity. Under non-uniform mineral distribution, the number of intergranular shear cracks far exceeds that of intergranular tensile cracks. • Progressive effect of mineral type on crack development: With a fixed total mineral content , the influence of quartz, feldspar, mica, and clay on the peak strength and elastic modulus of the specimen decreases successively. The number of cracks follows a descending order: matrix > clay > mica > feldspar > quartz. • Stage-controlled influence of mineral grain size on crack evolution: Mineral grain size affects different crack types at various stages: intragranular tensile cracks in the initial stage, intergranular shear cracks emerging in the stable propagation stage, dominant intergranular shear cracks in the unsteady propagation stage, and both intergranular shear and tensile cracks in the failure stages. The non-homogeneity of rocks mainly stems from the uneven distribution of mineral content and grain size, which affects the crack extension evolution and rock mass engineering stability. Taking coarse-grained sandstone as the research object, the mineral crystal models were established by polarizing microscopy test and PFC particle flow simulation. Uniaxial compression simulation tests were carried out to reveal the influence mechanism of mineral content and particle size on crack growth and evolution. The results show that when the total mineral content is 30%, quartz, feldspar, mica and clay have decreasing effects on the peak strength and modulus of elasticity of the specimens. Quartz affects tensile damage. The feldspar affects shear damage. The unequal ratio of quartz and feldspar aggravates the complexity of cracks. In the case of uneven distribution of the mineral content, the number of intergranular shear cracks is significantly larger than that of intergranular tensile cracks. The total number of cracks shows a decreasing trend of matrix>clay>mica>feldspar>quartz. There is a significant grain size effect on crack growth. The mineral grain size affects the intragranular tensile cracks in the initial stage. Intergranular shear cracks appear in the stable expansion stage. The effect is intensified in the unsteady expansion stage, mainly affecting the intergranular shear crack. In the stage of destruction and the complete destruction stage, the mineral grain size mainly affecting the intergranular shear cracks and intergranular tensile cracks. The results provide an essential basis for a deeper understanding of rock mechanical behavior and rock engineering stability assessment.
Liu et al. (Wed,) studied this question.