A review of the methods to incorporate the geological and geotechnical characteristics of rock masses in blastability assessments for selective blast design

Rock fragmentation by blasting is still among the most challenging of problems in geomechanical engineering.

The intent of this work is not to develop a new overall blast fragmentation model as the existing models, like Swebrec (KCO), the Fragmentation-Energy Fan, or the Distribution-Free models, have proven successful. The aim of the study is, however, to review the approaches that have been developed for rock mass blastability assessment. The desire to identify the three-dimensional (3D) distribution of the blastability of a rock mass for selective blast design inputs for Grade Engineering®, led to a review of blastability assessment approaches to determine the opportunities for continuous and automated assessment. The comprehensive review of over thirty blastability assessment approaches has shown how different geological and geotechnical parameters play various roles in the blastability assessments. The blastability assessment approaches to fragmentation are categorised based on their application (qualitative assessment, powder factor determination, or fragmentation prediction) or the source of the significant parameters (small -scale tests, rock mass measurements, geotechnical ratings, pre-blast indirect measurements, post-blast measurements, or multiple rock mass and blast measurements). Over twenty parameters were identified in the review, often with a high level of uncertainty associated with determining the effective parameters. The authors then show that there are three key factors which impact on the mechanisms of the dynamic breakage of rocks – the strength, density, and structure of the rock mass (discontinuities). The quantification of the discontinuities is not always considered although they are vital because the intrinsic block size distribution controls the fragmentation, governs the propagation and the attenuation of the stress waves in the rock mass, and the extent of the damage zone. This study also reviews approaches to assess the three dimensional blastability distribution of rock masses linked to modern rock mass measurement and geophysical surveys. A simple, rapid, and practical blastability assessment is key to advanced blast design.

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