At Usibelli Coal Mine (UCM), mining is primarily from seams 3, 4, and 6 of the Suntrana Formation. These seams average approximately 18' (5.5m), 30' (9.1m), and 24' (7.3m) respectively.
Up to 100 feet of unconsolidated sandstone or overburden must be moved to uncover the top seam (seam number 6) of coal. Another 120 feet of interburden must be moved to uncover the d seam (seam number 4) while roughly another 80 feet of interburden must be removed to uncover the third seam of coal (seam number 3) reaching nearly 400 feet at its deepest point.
Overburden is removed by four different methods:
1. The dragline removes the bulk of the overburden
2. Blasting utilizing explosives loosens and casts the overburden
3. Dozers move overburden short distances prior to drag line operations
4. Shovels strip and load overburden and coal into the haul trucks
The primary pieces of equipment utilized to remove overburden are the Bucyrus Erie 1300W walking dragline, a variety of bulldozers, various large dump trucks and shovels/loaders, and explosives conducting caste blasting operations.
The dragline has several buckets, which are used on a rotational basis. UCM utilizes several different configurations of bucket including 33-, 35-, and a high-production 42 cubic-yard bucket. Each bucket is used on the dragline for approximately 6 to 8 months. After that period, the bucket must be serviced and critical surfaces of the bucket repai ........
