GENERAL42809 - Laserfiche WebLink

Home Browse Search

III IIIIIIIIIIIIIIII 999 Auger Proves Itself in the West Coal augers have not been popular in the West, but GEC Minerals believes augering is an economical method of increasing coal recovery and productivity. Dan Jackson, western editor or the past five months in Colorado GEC Minerals Fhas been augering coal successfully-coal that would not have been recovered beyond the economical limit of the contour mining method used by the company. Li Chen, vice president of operations says, "We've increased our production substantially at lower crost by augering to a depth of 150 ft beyond our highwall limit. it's not just one seam but up to five with a combined thickness of 12 ft." The seams are thin compared to others in the West, the ratio of overburden to coal on the property averaging 13:1. But even with this ratio, productivity runs about 18 tons per manshift. GEC expects to produce 150,000 to 200,000 tons of coal in 1983 from this mine near Florence, Colo., and will increase production annually in increments of 50,000 tons to a maximum level of 300,000 tpy. At present the company is moving some 2 millon cu yd of overburden and interburden annually to produce the 150,000 tons. This overburden/interburden figure will. about double when the company reaches maximum production. "For- tunately," says Chen, "We won't have to add much in the way of major equipment to reach our goal-possibly a few trucks along with a tew auxiliary items." Hydraulic shovels move bulk of overburden The contour mining concept takes advantage of two 10-cu yd Demag hydraulic shovels and an auger to recover the five coal seams, which range in thickness from below 2 ft up to 6 ft. Benches, developed for each coal seam by first removing overburden and then inter- burden, are held to about 200 ft in length and 400 ft in width in the current pit. The East and North pits yet to be developed will be 500 tt and 800 tt wide, respectively. Bench heights vary, depending on overburden and inter- burden thicknesses. Overburden capping the top seam varies from 20 to 30 ft and interburden separating the first and second seam varies from 35 to 95 tt. The thickness o[ interburden between the remaining seams varies from 15 to 18 ft. The economical highwall limit at GEC averages 120 tt. .'Ti", t ~~p-:. .':~ ' ' Two Demag H-111 shovels will remove sufficient overburden and interburden to mine more than 300,000 ipy of coal. Some 900 ft of pit length must be mined before an active backfill area is established. Until then, the waste material is placed in temporary overburden stockpiles for use later in backfilling the final pit. Clearing and grubbing plant life with dozers is the first activity to take place in establishing a new bench. This is followed by topsoil and subsoil removal, using Terex 5-24 scraper loaders in combination with crawler dozers. Top- soil and subsoil are loaded and stored or redistributed on regraded areas. After the soils have been removed, the two hydraulic shovels begin loading colluvium that lies above the over- burden. This material is loaded into 35 and 50-ton Cater- pillar Terex end-dump trucks and hauled to the backfill area. Much of this material, consisting of river gravel, is used as a base for constructing in-pit and out-of-pit roads. Larger colluvium material is also used as riprap for lining diversion ditches, emergency spillways, or oth- er areas with high erosional characteristics. Removal of the colluvium exposes the overburden directly over the top seam, which must be drilled and • •