Dynamic characteristics and fracture morphology of two rocks with different length to diameter ratios
ZHOU Jun1, 2, ZHAO Guangming2, 3, MENG Xiangrui2, SUN Jinshan1, YU Meilu3, WANG Congcong3, YAN Pan3
(1. State Key Laboratory of Precision Blasting, Jianghan University, Wuhan, Hubei 430056,China; 2. National Key Laboratory of Safe Mining of Deep Coal and Environmental Protection, Anhui University of Science and Technology, Huainan, Anhui 232001, China; 3. State Key Laboratory of Digital Intelligent Technology for Unmanned Coal Mining, Anhui University of Science and Technology, Huainan, Anhui 232001, China)
Abstract： The differences in rock mechanical behavior significantly influence mine disaster protection. To investigate the size effect of granite and sandstone under dynamic impact, the impact compression tests on sandstone and granite specimens with length-to-diameter ratios of 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 using split Hopkinson pressure bar (SHPB) system at an impact pressure of 0.75 MPa were conducted. The stress-strain curves, compressive strengths, peak strains, and elastic moduli of sandstone and granite specimens with varying length-to-diameter ratios were examined. The analysis of energy for rocks with different length-to-diameter ratios is included. The differences between sandstone and granite during the impact process using digital image correlation (DIC) and sketches were compared, and the rock fracture morphologies were analyzed. Furthermore, the relationship between rock failure and slab length using the Euler formula were examined. The results indicate that the two types of rock exhibit distinct and common patterns. The stress-strain curve of sandstone is relatively “smooth”, while the slope changes at each stage of the stress-strain curve for granite are pronounced. The variation in sandstone strength with length is greater than that of granite. Specifically, the compressive strength of sandstone is positively correlated with the length-to-diameter ratio, increasing as the ratio rises. In contrast, granite shows no significant size effect on strength. The peak strains of both sandstone and granite are negatively correlated with the length-to-diameter ratio, decreasing as the ratio increases; notably, the reduction in peak strain for sandstone is more substantial than that for granite. The elastic moduli of both sandstone and granite are positively correlated with the length-to-diameter ratio, with both increasing as the ratio grows. However, the increase in elastic modulus for sandstone with length is less than that for granite. In these tests, transverse cracks were observed on the surfaces of both sandstone and granite. As the length increased, the energy dissipation per unit volume of rock decreased, and the energy dissipation rate for sandstone was lower than that for granite. Additionally, as the length-to-diameter ratio increased, both rocks were more susceptible to fracturing. The buckling stress of the surrounding rock exhibited a negative correlation with length under dynamic loading conditions. The findings of this study can provide valuable insights for the stability control of roadway surrounding rock.
周 俊1，2，赵光明2，3，孟祥瑞2，孙金山1，于美鲁3，汪聪聪3，燕 磐3. 高径比差异条件下花岗岩和砂岩动态特性及破裂形态研究[J]. 岩石力学与工程学报, 2025, 44(9): 2379-2390.
ZHOU Jun1, 2, ZHAO Guangming2, 3, MENG Xiangrui2, SUN Jinshan1, YU Meilu3, WANG Congcong3, YAN Pan3. Dynamic characteristics and fracture morphology of two rocks with different length to diameter ratios. , 2025, 44(9): 2379-2390.
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2025, Vol. 44 
