Document Type
Conference Paper
Publication Date
2020
Abstract
Conventional overburden removal in coal mining is typically achieved using drill and blast. However, drill and blast is a cyclical (or batch) process that has inherent inefficiencies and offers limited opportunities for enabling automation technologies. Existing mechanical rock cutting systems such as surface miners, continuous miners, road headers, impact hammers and tunnel boring style machines are commonly applied in underground excavation environments and also in some mining operations. Most of these technologies are based on pick-based machines, mechanical indentation and hammer impact. A review of industry literature and OEM data indicates that beyond rock strengths of about 40MPa UCS, the cutting cost for pick-based systems escalates exponentially due to high pick consumption rates and low machine productivity. However, with the emergence of undercutting with oscillating discs (developed by Joy Global as DynaCut™), potential exists for economic mechanical excavation spanning the broad range of typical coal overburden materials - even those well beyond 40 MPa UCS. This paper presents key findings from investigating the application of continuous cutting systems for surface coal mine overburden removal. Komatsu’s DynaCut rock cutting machine was used for cutting trials at a sandstone quarry, to quantify performance in representative rock domains typical of overburden material found in Australian coal operations: (a) low-strength (<30 MPa UCS); (b) medium-strength (~30-50 MPa UCS); and (c) higher-strength (+50/60 MPa UCS). In total, approximately 500 m3 of in-situ rock (overburden) was cut along a 40m bench section, with a 3m high x 5m wide working face. The quarry cutting trial successfully demonstrated the performance of the DynaCut technology in representative overburden material domains. A general trend of increasing specific energy of cutting (SE) with increasing material strength was reported. The SE ranged from about 1.0 MJ/m3 to 6.9 MJ/m3, averaging between about 3.5 MJ/m3 and 3.8 MJ/m3 across the three rock domains. The instantaneous cutting rate (ICR) ranged from about 35 m3/hr to 120 m3/hr. This field experiment has shown the potential for a DynaCut system (using undercutting technology) to provide a competitive solution for mechanical overburden cutting, particularly for materials beyond 40MPa UCS, where traditional cutting systems become rapidly ineffective and inefficient. Early field results indicate that an up-scaled DynaCut system could average around $2.00/BCM for a mine with a broad material spread up to >100 MPa UCS.
Publication Details
Isaac Dzakpata, Dihon Tadic, Joji Quidim, Application of continuous mechanical cutting to coal overburden removal, Proceedings of the 2020 Coal Operators' Conference, University of Wollongong - Mining Engineering, 12-14 February 2020, University of Wollongong, 186-197.