This mines' smallest excavator was a Hitachi EX3600 fitted with a 29 m 3bucket, with an effective utilization of 61%. Hence, the use of an excavator on the highwall might not be more economically favourable for mine sites that own only large excavators preferred for high-priority digging rather than secondary trenching tasks in dozer bulk push processes.Īn open cut thermal coal mine in the Hunter Valley in NSW, Australia (denoted as 'the mine site' throughout this paper) hired three D11R Caterpillar dozers specifically to perform bulk push operations on site for the first time. excavators smaller than 23 m 3bucket capacity). This statement, however, is based on the assumption that small ancillary-type loading units are used (i.e. Overall, current industry practices surrounding dozer bulk push operations suggest that the use of an excavator on the highwall is more productive and economically viable than dozer side-cutting.
Other perceived issues with dozer side-cutting include higher maintenance requirements and safety risks to dozer operators working in close proximity to the highwall. While dozer side-cutting is possible, it has been found that the majority of mine sites use a loading unit in this situation to avoid dozer inefficiency. However, when dozers are required to remove material off the highwall, they must push parallel to the highwall, rather than perpendicular, hence 'side-cutting' the material to ensure a clean face. In a typical bulk push operation, once the bench has been blasted, waste is left resting against the highwall, which can either be cleared using a loading unit or by having the dozers 'side-cut' the highwall.ĭozers perform most effectively when slot dozing side-by-side, perpendicular to the highwall. In the past decade, dozer bulk pushing has emerged and taken over from traditional waste removal operations such as dragline and truck-and-shovel methods at various sites around the world (Beatty, 1994). Optimizing the cost of waste removal operations is important for the profitability of opencast coal mines. Keywords: dozer push, excavator, side casting, side cutting. So, what happens if some mine sites are restricted to using relatively larger excavators (> 23 m 3 bucket) that are preferred for higher priority digging tasks? When can they avoid using their excavator? This paper explores multiple scenarios that have been designed and developed to simulate data results, which identify conditions in which the dozer side-cutting technique becomes more economically viable than excavator side-casting in terms of decreased unit cost per loose cubic metre. However, such excavator side-casting 'economic viability' assumes that smaller/ancillary type excavators are used (i.e. Industry practices suggest the latter technique is less productive and economical than using an excavator. An alternative technique is to have the dozers 'side-cut' the material, which involves the dozers running parallel to the wall, digging out the material, and eventually rotating their blades to begin bulk pushing. Instead, an excavator can be used to side-cast this waste for the dozers to access. This is because dozers cannot physically get in behind the waste to begin the bulk pushing process. In open pit dozer bulk push operations, the material left resting against the highwall after blasting poses an issue. School of Mechanical and Mining Engineering, The University of Queensland, Australia Dozer side-cutting' versus excavator side-casting on the highwall in dozer bulk push operations
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