Minero

Reducing Selectivity in Narrow-Vein Mining through the Integration of Underground Pre-concentration
Andrew Bamber, Bern Klein, Mario Morin, Malcolm Scoble Department of Mining Engineering, University of British Columbia, Vancouver, Canada

Abstract The introduction of pre-concentration technology into the underground narrow-vein mining scenario has the potential to change the entire economicsof utilizing bulk-mining methods in these situations. An idealized integrated underground mining and processing system, comprising elements of bulk mining, underground preconcentration and backfill systems is presented. Through simulation and a systems engineering approach, the implications of enabling the utilization of bulk mining methods in a narrow vein deposit through the adoption of thistechnology is considered. Parameters considered include orebody characteristics, ore mineralogy, grade, metal value, mining rate and cost. Keywords – narrow-vein mining, bulk methods, underground pre-concentration, backfill, economics

1.

Introduction

The majority of Canadian hard-rock narrow-vein mines are mature, and face the need to mine deeper deposits in the face of increasing costs anddeclining grades. Obstacles to the successful mining of such deposits include ground control, material handling and ventilation. In addition to these issues, the mining of narrow-vein deposits faces additional economic challenges in the low productivity of the typical narrow-vein mining method, the management of dilution and therefore grade, and the optimal integration of fill into the miningcycle. UBC has been involved with INCO in a strategic research initiative into mine-mill integration, and more specifically underground pre-concentration, since 2000. Several enabling technologies such as coarse-particle mineral processes, hydraulic transport and modular cemented backfill systems have been identified, and integrated using systems engineering techniques into a conceptual undergroundmining and processing system for the rejection and disposal of waste. The grade of ore delivered to surface is substantially increased through the rejection of barren waste underground. Previous research has indicated that substantial operating and capital cost savings can be achieved, as well as a reduction in the surface footprint of the operation. A case study has been undertaken forFalconbridge’s Onaping Depth Deposit in Sudbury, Ontario to assess the potential impacts of underground pre-concentration. Geological research and mineralogical evaluation of typical Sudbury Igneous Complex ores indicate that between 20 – 70% of the ore mined can be rejected with a good metallurgical recovery. Several coarse-particle separation technologies have been identified and tested for use in theunderground process plant. Waste thus rejected is highly competent, and is suitable for use as a source of aggregate for cemented backfill of superior mechanical properties. A conceptual process plant has been developed and integrated into the underground mining and material handling system. Several impacts of the implementation of underground pre-concentration on the operation have been identified,including: • Lowering of the cost of metal production through rejection of up to 60% dilution underground at greater than 95% metal recovery • Savings in underground haulage, hoisting, surface transport, milling and tailings disposal • Lowering the cutoff grade through the reduction in operating costs • Increasing the mineral reserve though lowering of the effective cutoff grade • Decrease inselectivity of mining, thus increasing productivity • A possible increase in minimum stoping height (ground conditions permitting), facilitating the use of more productive mining equipment and the introduction of automated roof-bolters • Potential change in mining method to bulk-mining techniques due to the inclusion of a continuous, efficient and effective waste-rejection step within the mining cycle...