Pullback mode dragline stripping in dipping coal seam
This study presents the results of a computer-based model developed for analysing the pit geometry formed when a dragline operates in pullback mode. Basically, three spoiling procedures are modelled for a flat or an inclined coal seam. The normal operation model explores the conditions for dragline employment with a flat coal seam. Inclined model on the other hand, is divided into two parts: the uphill operation model where the dragline spoils uphill and the downhill model where the dragline spoils downhill. Two spoiling arrangements axe embedded into pullback model: waste is placed into the room near the set on which the dragline is located (DNS arrangement) or into the room near the set the dragline excavates (DND arrangement). Waste dug from key cut is placed on three main points: at the toe of previous spoil pile (distant), at the toe of coal seam (near) and within adjacent empty pit (middle). The pullback model also studies geometrical requirements on the spoil side. The model primarily indicates that dragline operation is sensitive to coal seam inclination. The uphill spoiling practice places much tighter constraints on geometrical dimensions than the downhill practice. In all spoiling procedures, the DNS arrangement offers much wider pit width ranges and lower rehandle percentage.