Development of an assessment system for the blastability of rock masses

Intact rock properties and the discontinuity structure of a rock mass are among the most important variables influencing blasting results. This influence is considered to be a composite intrinsic property of a rock mass and is referred to as the blastability of a rock mass. It represents the ease with which a rock mass can be fragmented by blasting. This paper outlines an energy-block-transition model, recently proposed by the authors for characterising the blast process. A preliminary validation of this model using two sets of field data from the literature is briefly outlined. The model is comparable or better than Bond`s comminution theory at predicting blasting results for cases where intrinsic rock properties are relatively constant. To generate a predictive capability for the model, a blastability designation BD, is designed which reflects the intrinsic resistance of the rock mass to blasting. The quantification of BD, based on rock engineering systems approaches and consideration of a comprehensive range of intact rock properties and discontinuity structures is illustrated. A case study is given which applies the model and the associated assessment system to a highway cutting site. Confidence as to the potential value of the assessment system and the model is obtained since refinement and improvement on pre-existing models can be seen from the new preliminary results. (C) 1999. Published by Elsevier Science Ltd. All rights reserved.