Experimental Study on Dynamic Tensile Mechanical Properties of High and Low Grade Iron Ores

During the mining process, tensile failure represents a predominant mode of ore fragmentation. This research systematically examines the dynamic tensile mechanical properties of both high-grade (Fe > 60%) and low-grade (Fe 10 ~ 20%) iron ores through the combined application of Split Hopkinson Pressure Bar (SHPB) testing and Ultra-high-speed Digital Image Correlation (DIC) techniques for dynamic splitting tests. The analysis focused on failure mechanisms, strain field evolution, dynamic tensile properties, and energy absorption capacity. Results reveal that high-grade iron ore specimens experience localized crack propagation at their geometric center, predominantly failing through the formation of a dominant central fracture. A strong positive correlation was observed between increasing impact pressure and improvements in both dynamic tensile strength and loading rate. In contrast, low-grade iron ores exhibit dispersed crack propagation along pre-existing internal joints due to their structural heterogeneity. The dynamic tensile strength and loading rate exhibit less predictable trends in these specimens, which are predominantly governed by joint network characteristics. Energy dissipation analysis indicates superior energy absorption capacity in high-grade ores, where failure mechanisms are primarily determined by mineral grain strength, while low-grade ore failure is dictated by joint plane integrity. Comparative analysis reveals that under identical impact pressure conditions, high-grade iron ores exhibit superior mechanical performance compared to low-grade specimens, with higher loading rates, dynamic tensile strength, peak tensile strain capacity, and energy absorption. This study confirms the substantial influence of both lithological characteristics and ore grade classification on mechanical properties. These findings establish a theoretical framework for optimizing blasting parameters and implementing effective damage mitigation strategies in iron ore mining operations.