The impact load cell as a tool to link comminution properties to geomechanical properties of rocks

Current tests for characterising rock breakage in comminution do not allow decoupling of rock breakage properties from the machine environment. Furthermore, it is difficult to predict the comminution behaviour of different ores or how they might behave in another breakage device. Consequently, this decoupling process is essential for comminution modelling of variable ores and blends, which interact with different breakage equipment. Previous studies have shown that the Short Impact Load Cell (SILC) is a versatile tool for characterising the primary ore breakage properties such as strength, apparent stiffness and mass-specific fracture energy, regardless of breakage environment. However, its potential as an ore characterisation technique to relate these mechanical properties to the ore characteristics (e.g. mineralogy, texture) has not been investigated in detail. In this first paper, the results from breaking cylindrical and irregular particles from different ore types in the SILC and Slow Compression Testing demonstrate the SILC's ability to accurately measure strength, stiffness and specific energy of different ore types at different particle sizes which is relevant either for comminution modelling or for rock mechanics testing. The results of breaking cylindrical particles of nine different rock types show that the SILC is capable of matching the results of the slow compression machine for Indirect Tensile Strength from the Brazilian Test and the apparent stiffness results from the Uniaxial Compression test, allowing the accurate calculation of the mass-specific fracture energy distribution for each rock at different sizes. In addition to the cylindrical samples, sets of irregular particles were produced for three rock types and were broken with the SILC. The results show that the median values of strength and stiffness do not change significantly with the shape of the particle, but the standard deviation does increase when irregular particles are tested. If these results are compared with the cylindrical particle results, it can be seen that the geological characteristics of the rock control the median values of the parameters. When the variation around median value is considered it is apparent that particle shape exerts the major control, but geological characteristics still contribute up to 30% of the variation in strength, 25% in stiffness and 25% in the mass-specific fracture energy. The results indicate that the SILC is a suitable device that allows measurement of the primary breakage properties relevant to comminution, which can be easily associated with the geomechanical properties of the rock mass and geological characteristics. The further development of the proposed testing methodology can provide a more comprehensive and less empirical comminution testing for future modelling, incorporating geological and geomechanical properties of the rock.