Open Cut » Overburden Removal
This project enabled investigation of potential cutting technologies for use in a High Capacity Surface Continuous Cutting (HCSCC) system for coal mine overburden, identifying technology gaps and risk mitigation strategies for commercial implementation.
Key requirements were linked to cost and productivity competitiveness with current mining systems, targeting replacement of drill/blast/load at a scale similar to a large mining shovel i.e. approximately 40 Mtpa per system (potentially several cutting machines operating in unison) with an all-in cost of about $2.00/BCM. Cutting rates and costs for various existing and emerging technologies for the full range of overburden material characteristics were estimated based on data and information from OEMs, existing operations, and some new laboratory testing. Of the selection of OEMs approached to participate in this project, Joy Global, Sandvik and Wirtgen agreed to contribute and provided significant information to assist the investigation and assessment.
Conventional mechanical rock cutting systems include pick-based and indenter-based machines such as surface miners, continuous miners, and various tunnel boring style machines. The most suitable of the conventional machines for mass mining of overburden appear to be the pick-based machines, which could be up-scaled for higher production rates; however, these are only suited to lower-strength overburden materials i.e. typically below 40 MPa UCS.
The emerging technology of undercutting with oscillating discs (being developed by Joy Global as Dynacut) has potential to improve upon current pick-based machines and, critically, provide a competitive solution for materials above 40 MPa UCS. Development of a commercial Dynacut system within the target timeframe (2020) will require further R&D into the cutting mechanism in coal overburden materials and a focused engineering effort.
A simple financial model was developed to allow preliminary assessment of the machine options, costs and productivity for specific mining scenarios. Analysis indicated that whilst the costs for cutting of materials below about 30 MPa UCS is likely similar for pick-based and undercutting disc systems, at around $1.00-$2.00/BCM, the emerging undercutting disc technology may be competitive across the full range of overburden materials. With a modest improvement in cutting costs through further technical development, the undercutting disc systems could average around $1.00/BCM for a mine with predominantly low-strength (<40 MPa) material, and around $2.00/BCM for a mine with a broad material spread up to >100 MPa UCS.
Based on the technology gaps associated with the high-potential continuous cutting systems for this application, a de-risking development strategy shaped three key recommendations:
· ACARP should invest in additional R&D to quantify the potential performance characteristics (with site demonstrations) of the undercutting disc technology;
· The Mining Industry should work with pick-based surface miner OEMs to quantify the cutting performance and consumables costs of existing commercial machines across overburden material classes; and
· ACARP should invest in additional R&D related to operational models and optimisation techniques to maximise the potential benefits for a HCSCC system in Australian surface coal mines.