Blastability and Ore Grade Assessment from Drill Monitoring for Open Pit Applications

• Published in: Rock mechanics and rock engineering Vol. 54; no. 6; pp. 3209 - 3228
• Main Authors: Navarro, Juan, Seidl, Thomas, Hartlieb, Philipp, Sanchidrián, José A., Segarra, Pablo, Couceiro, Paulo, Schimek, Peter, Godoy, Clara
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.06.2021; Springer Nature B.V
• Subjects: Blasting; Civil Engineering; Corrections; Design parameters; Drilling; Drilling rigs; Drills; Earth and Environmental Science; Earth Sciences; Geology; Geophysics/Geodesy; Identification; Limestone; Mathematical models; Monitoring; Original Paper; Parameters; Principal components analysis; Properties; Quality assessment; Rock mass rating; Rocks; Sandstone; Sedimentary rocks; Siderite; Strength; Structural properties (geology); Transition zone; Unmanned aerial vehicles; Waste identification; Rock structural factor; Ore grade recognition; Measurement while drilling (MWD); Blasting; Automatic rock classification; Block model; Open pit; Assaying
• ISSN: 0723-2632; 1434-453X
• DOI: 10.1007/s00603-020-02354-2

Blasting performance is influenced by mechanical and structural properties of the rock, on one side, and blast design parameters on the other. This paper describes a new methodology to assess rock mass quality from drill-monitoring data to guide blasting in open pit operations. Principal component analysis has been used to combine measurement while drilling (MWD) information from two drill rigs; corrections of the MWD parameters to minimize external influences other than the rock mass have been applied. First, a Structural factor has been developed to classify the rock condition in three classes (massive, fractured and heavily fractured). From it, a structural block model has been developed to simplify the recognition of rock classes. Video recording of the inner wall of 256 blastholes has been used to calibrate the results obtained. Secondly, a combined strength-grade factor has been obtained based on the analysis of the rock type description and strength properties from geology reports, assaying of drilling chips (ore/waste identification) and 3D unmanned aerial vehicle reconstructions of the post-blast bench face. Data from 302 blastholes, comprised of 26 blasts, have been used for this analysis. From the results, four categories have been identified: soft-waste, hard-waste, transition zone and hard-ore. The model determines zones of soft and hard waste rock (schisted sandstone and limestone, respectively), and hard ore zones (siderite rock type). Finally, the structural block model has been combined with the strength-grade factor in an overall rock factor. This factor, exclusively obtained from drill monitoring data, can provide an automatic assessment of rock structure, strength, and waste/ore identification.