采礦工程畢業(yè)設(shè)計(jì)英文翻譯畢業(yè)論文-展示頁
2024-12-14 00:17本頁面
【正文】 s often severely limits the size of a mining section, forcing frequent moves and excessive development work. The thickness of the overburden results in very high ground pressure. This would require extremely large pillars if the room and pillar method was applied. Additionally, support is required for any opening, adding prohibitive costs to a multipleentry room and pillar operation. As a result, singleentry longwall operations requiring the minimum number of entries and allowing maximum recovery of resources is the mining method almost exclusively practiced. Shaft mines dominate the European coal mining industry. Shafts 20 to 30 ft in diameter, with circular cross section, lined with masonry, concrete, or steel are the dominant means of gaining access to the coalbearing strata. They are often extended beyond the last mining level to provide for future expansion. As in the Unite States, shafts are developed by drilling, blasting, and excavating or by largediameter shaftboring equipment. Shaft boring is more frequently used, particularly 2 on the smaller and shorter subshaft, which connect the different levels but do not extend to the surface. Haulage in the shaft is usually acplished by hoisting of the filled mine cars on multistage cages or by skips. Pumping of coal slurry is also done in special cases. The plex system of forces and the resulting rock mechanical problems developed by mining activities at different levels result in significant differences between European and US underground development. The
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