Effect of cleavage characteristics of mineral grains on the failure process of hard rock based on UDEC-GBM modeling

Based on the UDEC (Universal distinct element code) modeling and grain-based model (UDEC-GBM), the effects of mineral’s (e.g., feldspar) cleavage angle, the confining effect of the cleavage angle and cleavage spacing on mechanical properties, microcracking process and mechanism of hard rocks, and the resulting problems in engineering were investigated in the present study. Numerical results show that: (1) Mineral cleavage has a considerable angle effect. As the cleavage angle increases from 0° to 90°, the elastic modulus, uniaxial compressive strength, and post-peak characteristics of the rock are affected. The total number of transgranular cracks is obviously affected, which is mainly reflected by the increase in the number of feldspar tensile cracks and the number of feldspar shear cracks increases to a maximum at 60° and then decreases, and the number of quartz tensile cracks changes considerably. In general, the number of transgranular cracks increases, while the number of intergranular cracks decreases. However, tensile and intergranular cracking dominate the cracking process. (2) The cleavage effect is affected by the confining pressure. The confining pressure will cause the number and proportion of intergranular cracks and transgranular cracks to change. However, the confining pressure at different angles has different effects on the number and proportion of intergranular cracks and transgranular cracks. (3) As the cleavage spacing increases from 2 to 4 mm, the number of transgranular cracks increases and the number of intergranular cracks decreases. However, the ratio of the total shear and tensile cracks remains constant, indicating that microscopic tensile and shear cracking mechanisms are almost unaffected. In addition, when the proportion of minerals with cleavage characteristics is high and the type of mineral has a considerable influence on the rock properties, the influence of cleavage characteristics on rock failures, such as spalling and rockburst, should be given attention.