Equivalence study of granite and reinforced concrete targets under penetration based on modified compensation method

Due to the challenges associated with material acquisition and high costs in penetration tests on granite targets, research on the equivalence between reinforced concrete (RC) and granite targets has been conducted. This study employs dimensional analysis and a modified compensation method, with the residual velocity as the equivalence criterion, to derive a computational approach for equivalent thickness. Based on existing experimental studies, a numerical model for medium-velocity projectile penetration into targets is established using LS-DYNA software and numerical simulation techniques. By considering projectile dimensions, impact velocity, and target thickness as variables, typical working conditions are designed. Through data fitting, a specific equivalent design formula for granite and reinforced concrete targets is obtained. The results indicate that the developed numerical simulation model accurately captures the residual velocity of the projectile and the failure characteristics of the targets during penetration. In the penetration process, compared to reinforced concrete targets, granite targets exhibit a smaller compaction zone and tunnel diameter, finer and longer cracks with higher propagation speeds, larger crack areas on the target surface, and a tendency to form larger spalling craters. Under identical penetration conditions, the failure characteristics of granite and equivalent-thickness reinforced concrete targets are similar, with both targets exhibiting five distinct failure regions. Using dimensional analysis and the compensation correction method, a dimensionless residual velocity function for projectiles penetrating reinforced concrete and granite targets is derived, along with an equivalent thickness formula for the two target types. The fitted equivalent thickness coefficient between granite and reinforced concrete is determined to be 1.69966. Validation of the equivalent thickness design formula using this coefficient shows that the error in residual velocity between the prototype and model targets does not exceed 5%. The findings of this study provide a valuable reference for the equivalent design of rock targets subjected to medium-velocity projectile penetration. The present work contributes to the field by offering a systematic methodology for substituting