Numerical Investigation on the Influence of Rock Block Gradation on the Mechanical Behavior of Bimrocks

ABSTRACT Differences in block gradation are common in bimrocks and exert a significant influence on their mechanical behavior. This study employs the 3D discrete element method to investigate the effects of block gradation in specimens with volumetric block proportions (VBPs) between 30% and 60%. In addition, the roles of block shape and block distribution in modulating the influence of block gradation are examined. Results indicate that at 30% VBP, block gradation primarily affects the peak strength and corresponding strain of specimens. When VBP ranges from 40% to 60%, its influence on peak strength becomes more irregular; however, the elastic modulus is lower in specimens with a higher proportion of small blocks. Such specimens are also more prone to through‐going failure, whereas those containing larger blocks tend to exhibit localized failure. Specimens with ellipsoidal blocks are more susceptible to through‐going failure, as block shape strongly affects fracturing within the matrix, at matrix–block interfaces, and within the blocks themselves. Block distribution exerts the greatest influence when the proportions of blocks of different sizes are relatively balanced.