Abstract
This study aims at proposing an innovative technique to reliably characterize the rock masses for differential blast design to optimize rock fragmentation. A few key technologies and approaches for acquiring and delivering the required information for blast design are identified and briefly explained. This study shows that proper design of differential blasting for Grade Engineering® needs accurate information related to the three-dimensional (3D) distribution of Rock Mass Blastability, Grade, and Rock Response Factor. Rock mass blastability represents the dynamic resistance of rock masses to applied blast loads. There is currently no widely-accepted approach for assessing the blastability of rocks. This study indicates that a reliable rock mass blastability assessment should include some forms of rock mass strength, structure and density as the primary inputs. Blastability is typically calibrated to the rock mass using measured fragmentation of the blasted muck-pile. Input parameters for blastability are usually inferred from a limited amount of geotechnical testing data. This research; however, proposes that it is better to directly calibrate the blastability from measured geotechnical and geophysical parameters. The critical factors to include in the blastability assessment should be a representation of the rock mass strength, fracture frequency, and density. It is possible to characterize the rock mass using seismic P-wave speed linked to rock mass strength and stiffness, S-wave attenuation or geophysics quality factor (known as seismic Q), linked to fracture density and S-wave splitting linked to fracture direction. Other complementary techniques such as electromagnetics may also assist in increasing confidence in predictions between softer rock and hard-fractured rocks. The outcomes of geotechnical and geophysical tests, and remote sensing techniques can then be integrated to reliably identify the distribution of the grade and rock mass blastability across the blasting bench. A blast optimizer tool, developed by Usami et al. (2019), is then used for differential blast design in the characterized bench. The tool optimizes the rock fragmentation based on the theories of conventional rock blasting and the concepts of Mine to Mill optimization and Grade Engineering.
