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2024-12-10 00:17本頁面
【正文】 on in a steeply pitching seam mined manually with air picks。 (9) road heading machine (10) longwall section with plow。 (7) main entry。 (5) blind shaft with carhoisting facilities。 (3) thirdlevel station。 1 Underground Mining Most presentday mining in Europe occurs under 2021 to 4000 ft of overburden, as more easily mined coal deposits have been depleted. At this depth most mines are developed as shaft mines. All personnel, material, and coal have to be hoisted trough these shaft. Considering the two factors of hoisting capacity and required length of shaft, a considerable investment is necessary to reach the coalbearing strata. The requires huge investments. Openings at this depth have to be equipped with costly supports, and periodic reworking and repair is necessary. Mines not only extend horizontally but also vertically through the development of new levels. The life of the mines is thus extend considerably, and surface installations can be amortize over a longer period. The more limited reserves have forced panies into mining less favorable deposits, and European government require that all possible deposits be mined to conserve the nation’s energy resources. These factor and the large percentage of inclined seams and faults make mining very difficult and costly. The population density and the heavy surface buildup cause additional expense in the form of payments for subsidence damage to surface structures. Therefore, backfilling is frequently practiced to reduce subsidence. The close spacing of fault
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