Rock Mechanics
Shadman Mohammadi Bolbanabad; Masoud Monjezi; Vahab Sarfarazi
Abstract
The characteristics of fragment size distribution caused by blasting operations in open-pit mines have a direct impact on the economic performance and productivity of mining companies. In this study, dynamic impact loading tests were carried out using the Split Hopkinson Pressure Bar (SHPB) system under ...
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The characteristics of fragment size distribution caused by blasting operations in open-pit mines have a direct impact on the economic performance and productivity of mining companies. In this study, dynamic impact loading tests were carried out using the Split Hopkinson Pressure Bar (SHPB) system under a constant pressure of 12.5 MPa to investigate the influence of both the edge notch length and its position relative to the incident bar on the size distribution of fragmented iron ore. By analyzing the fragmentation distribution characteristics of specimens subjected to controlled laboratory impact loading, this study focuses on fundamental rock breakage mechanisms relevant to blasting operations in open-pit iron ore mines, where the fragmented material classified into three particle size categories: large, medium, and fine fragments. Based on this classification, the variation in the mass percentage of fragments with respect to notch length and its position relative to the incident bar was investigated. Ultimately, within the context of laboratory-scale fragmentation analysis, an effective range of notch lengths and positions relative to the incident bar was identified for achieving optimal fragmentation. The results revealed that a notch length between 0.2 and 0.4 and a notch position between L/2 and 2L/3 from the incident bar (where L equals sample length), produced the most favorable fragment size distribution. These findings can help link laboratory-scale fracture behavior to field-scale rock fragmentation considerations and contribute to a broader understanding of breakage processes in mining engineering.
Rock Mechanics
Shadman Mohammadi Bolbanabad; vahab sarfarazi; Masoud Monjezi
Abstract
One of the critical steps in experimental research is the precise preparation of specimens. This study aims to develop and present a comprehensive methodology for preparing magnetite iron ore specimens containing non-persistent edge notches for dynamic testing, as well as iron ore and ice specimens for ...
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One of the critical steps in experimental research is the precise preparation of specimens. This study aims to develop and present a comprehensive methodology for preparing magnetite iron ore specimens containing non-persistent edge notches for dynamic testing, as well as iron ore and ice specimens for uniaxial and Brazilian tests. Core drilling was performed using diamond drills with diameters of 54 mm for uniaxial and Brazilian tests and 22 mm for dynamic Split Hopkinson Pressure Bar (SHPB) tests. Non-persistent edge notches with a thickness of 3 mm, controlled length, and inclination were created using a cutter, and their geometric quality was verified through meticulous inspection. For ice specimens, filling the notches with water in tubes matching the specimen diameter provided optimal uniformity and stability. Additionally, precise control of parameters such as core and drill parallelism, drilling speed, cooling water flow, and environmental conditions (dry, saturated, and frozen) preserved the structural integrity and quality of the specimens. The results demonstrated that systematically following these procedures, along with detailed documentation of geometric and environmental specimen features, enables the production of intact, standardized, and reproducible specimens, ensuring reliable and consistent examination of the mechanical response and fracture of magnetite iron ore under both dynamic and quasi-static conditions.
