The grade control process undertaken at mines aims to maximise the value of the ore (valuable product) mined and fed downstream for processing or sale. The full range of grade control activities includes: reserve estimating, drilling/sampling, assaying, modelling, ore block design, blasting, ore mark out, excavating, stockpiling, processing and reconciling. Over the last 25 years, the grade control process has undergone significant improvements and this is in part due to the developments in grade control blasting. This paper discusses the development and classification of grade control blasting applications in surface mining. A review by the author in 1988 (Little and van Rooyen, 1988) is used as a benchmark for discussing the very significant progress that has been made.
Two major technology initiatives have enabled this development. The first was the development of a method for the measurement and analysis of total displacement during the blasting process. Currently, the Blast Movement Monitor (BMM®) is a practical tool that has been used around the world to improve the industry's understanding of three-dimensional blast movement dynamics. The second technological enabler was the development of electronic detonator systems. The unique aspects of electronic detonating systems are their higher accuracy and that all detonators are activated at time zero (initiation). From a grade control blasting perspective these features and other improvements allow experimentation and, ultimately, more complex, multiobjective blasts to be designed and implemented.
This paper reports on a classification and review study undertaken by the author. In all, five selective blasting methods and nine bulk blasting methods are classified and reviewed. Five important observations are made:
there is value in classifying the range of grade control blasting strategies, and the blasting objective framework presented is helpful in this regard
the range of strategies available to designers is increasing
as enabling technology develops, so too do the ambitions of blast designers and the expectations of downstream customers
grade control blasting and Mine to Mill concepts are merging, and this paper caters for this trend using multiple blasting objectives
having a technical primary blasting objectives framework, combined with the classification system presented here, should assist practitioners and stakeholders with lateral thinking in regards to future technological innovations, grade control blasting and Mine to Mill initiatives.
Little, T N, 2015. Classification and development in grade control blasting for surface mines, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 343–354 (The Australasian Institute of Mining and Metallurgy: Melbourne).