Issues with transitioning from open pits to underground caving mines

Abstract

This paper covers the issues and trends associated with transitioning from an open pit operation to an underground caving mine. The decisions made on the timing of the transition affect many parameters including the Mineral Resources (Resources) and Ore Reserves (Reserves), the timing and costs associated with the studies required to support the change. Fundamental issues such as the size of the underground operation and the anticipated ramp-up are discussed as well as the options afforded by Hybrid Caves (a Sub-Level Cave (SLC) later converting to a Block or Panel Cave (BC, PC)). The economics and risks of these strategies are discussed as well as the resultant impacts on traditional financial metrics. The authors believe that an holistic approach to evaluating the transition from open pit to underground is required, not simply an open pit optimisation, followed by a transition to an underground mine. Operations generally do not allow sufficient time, or plan the pre-requisite drilling programmes early enough, to make properly informed decisions about the transition.

Access to Deposits as a Stage of Mining Works

“…It is worth mentioning that more and more raw materials (metals) are obtained from urban mining [3,4] and that a new field of science related to the exploitation of deposits in space is developing [5]. Among the methods mentioned, most of the workings are carried out in underground mining, and this trend will continue because shallow deposits, after reaching the maximum level of the floor, are transferred to underground mining [6,7]. An extremely important aspect when making a decision to continue exploitation is the model of the deposit [8] along with the estimation of the amount of resources that will be extracted to the ground surface by means of access workings.…”

Procedure for estimating broken ore density distribution within a draw column during block caving

“…Several studies further indicate that broken ore undergoes a change in the BOD/swell factor along the ore column (Ross and Van As 2012; Sharrock et al 2012). This has also been identified in sublevel caving by Rustan (2000) who noted that properties like swelling, packing, and porosity vary so much in space and time during the gravity flow of coarse rock that analytical and numerical simulations using constant properties will always be questionable.…”