This study aims at comparing experimentally single, double, and triple spiral (scroll) cutting patterns for improving performance prediction models based on linear cutting tests. Full-scale linear cutting tests are performed by using a heavy duty conical cutting tool used mostly with roadheaders, shearers, continuous miners, and surface miners. The tests are performed at line spacing of 25 mm and varying cutting depths per revolution by using a travertine sample, which is considered as ductile and soft. Comparison criteria are average normal, cutting, and side forces, specific energy, and yield. Preliminary results indicate that normal forces increase highly with increasing spiral number, which is important for thrust limitation of miners, while cutting force and specific energy increase slightly. Results indicate that it is better to use lower number of spirals for soft and ductile rocks. However, additional tests are continuing to generalize the results including different types and strengths of rocks.
Excavation machine selection, design and performance prediction are the major issues influencing the profitability of using a mechanical miner. The adverse effects of inaccurate machine selection, design and performance prediction are lower production rates, higher machine breakdowns and cutter changing/replacement rates, lower machine utilization time, and thus, higher costs. All these problems sometimes make the project uneconomic or inapplicable. The major reason causing these problems is considered to be the lack of knowledge in rock cutting mechanics.
Cutterheads of partial-face mechanical miners such as roadheaders, shearers, continuous miners, and surface miners are rotary type and mounted with drag type (conical or radial) cutting tools. Cutting pattern of partial-face mechanical miners are usually organized in at least a few spirals (scrolls, sequences). Full-face excavation machines such as Tunnel Boring Machines (TBMs), microtunnel boring machines, and raise boring machines have also rotary cutterheads. Cutterheads of full-face miners for excavating hard rock are usually equipped with rotary cutters (disc cutters, multi-row disc cutters, strawberry cutters) in one spiral pattern. The cutting tools of continuous belt type linear motion machines such as chain saws are usually arranged also in one spiral (scroll) pattern (Copur 2010, Copur et al. 2011).