Effect of rock mass properties on blast fragmentation in central Iran iron ore mines

Rock mass properties are one of the important factors affecting the results of the blasting. In this study, in regard to the importance of optimal fragmentation in mining tried to investigate the effect of these properties on the size distribution of fragmentation in the study area including Choghart, Chadormalu and Sechahun iron ore mines. To achieve this purpose, the properties of the rock mass along approximately 1961 meter scanlines and 1771 meter seismic profiles was evaluated in 51 blasting blocks. Also digital image processing technique was used in order to measure the blasting fragmentation. For this purpose with the processing of 1500 images taken from the surface of muck piles was obtained size distribution of fragmentation. Fragmentation changes according to the rock mass properties showed that with increasing of spacing, persistency, aperture, roughness and wavy surface of discontinuities, increasing of uniaxial compressive strength and longitudinal wave velocity in intact rocks and increasing of being close angle between discontinuities strike and free surface strike of blasting blocks to 90°, blasting material size are also increasing. The results indicate that the rock mass properties impact on the size of blasting materials.