How can an intensive preconditioning concept be implemented at mass mining method? Application to Cadia East panel caving project

Broadly speaking, preconditioning as applied to cave mining is a process conducted prior to the initiation of caving in order to alter the inherent characteristics of the rock mass to enhance caving. To date preconditioning using hydraulic fracturing in particular has been implemented and reported to produce measurable and positive outcomes even though there is still on-going debate on the real impact of preconditioning with respect to cave mining performance. The Newcrest Mining Limited's Cadia East (CE) underground project is expected to become one of the largest and deepest caving mines in the world and certainly in Australia. In order to make the project economically viable required the application of a large scale and low cost underground mass or cave mining method in order to also achieve the required production rates (26Mpta). As such, panel caving was selected as the caving option. The extraction level of the first CE panel cave (PC1) is located 1,200m below surface and for the second lift (PC2) 1,400m also below surface. At Cadia East Project a novel approach locally designated as "Intensive preconditioning" is being applied. This uses a combination of hydraulic fracturing (in down-holes) and fully confined blasting (in up-holes). This paper describes the work that has been carried out to date and how technical and operational parameters have been assembled and implemented in order to incorporate the intensive pre-conditioning process. Copyright 2012 ARMA, American Rock Mechanics Association