<p>To minimize the influence of particle morphology and fragmentation on the strength and deformation evolution of coarse-grained soils, spherical glass beads were employed in isotropic consolidation and conventional triaxial compression tests. These experiments aimed to investigate the effects of particle size, mass ratio, and confining pressure. The results indicate that during shear processes, the void ratio gradually decreases with increasing confining pressure. Under identical confining pressures, the compaction capacity varies significantly among specimens with different mass ratios. Specifically, the compaction capacities of the void ratios (<i>e</i>_cap) in the 1:1 and 4:1 mass ratios are notably higher than that of the 1:4 mass ratio. Based on the strength parameters and deformation characteristics (<i>q</i>, <i>ε</i>_r, <i>ε</i>_v) of the specimens with mass ratios of 1:1, 4:1, and 1:4, it is evident that a well-balanced combination of coarse and fine particles with better interlocking (1:1 and 4:1) demonstrates higher shear strength and more uniform deformation. Conversely, the 1:4 mass ratio exhibits inferior stability. This phenomenon may be attributed to the complexity of particle arrangement and the evolution of pore structure. Accordingly, a fractal model incorporating correlations between pore-size and particle-size distributions was employed to investigate the underlying mechanisms of the specimen. The results indicate that specimens exhibiting minor variations in <i>D</i>_c (the consolidation-state fractal dimension) and <i>D</i>_cap (the compaction-induced fractal dimension) demonstrate superior structural stability, whereas <i>D</i>_0.25 displays pronounced variation amplitudes and a marked tendency for slippage occurrence. The results establish the fractal dimensions (<i>D</i>_c, <i>D</i>_cap) as indicators of structural stability, providing theoretical and practical guidance for optimizing fill material design in geotechnical engineering.</p>