APPLICATION OF BLASTING IN DRIVING TUNNEL中英文对照 采矿工程专业--毕业设计论文.docxVIP

APPLICATION OF BLASTING IN DRIVING TUNNEL1 FRAGMENTATIONFragmentation is the breaking of coal, ore,or rock by blasting so that the bulk of the material is small enough to load, handle and transport.Fragmentation would be at its best when the debris is not smaller than necessary for handling and not so large as to require hand breaking or secondary blasting .Energy must be supplied to rock by direct or indirect means to fragment that rock and the type of loading system.Fragmentation energy is consumed by the main mechanisms: (1) creation of new surface area (fracture energy), (2)friction (plasticity) and (3)elastic wave enegy dispersion.The loading method determines the relative proportions and the amount of energy consumed in fragmenting a given rock type. Unonfined tensile failure consumes the least energy with an increasing a,mount of energy required as the rock is more highly confined within a compressive stress field during fragmentation The way energy is applied by tools to cause rock or mineral fragmentation is important in determining fragmentation efficiency. To best design fragmentation tools and optimize fragmentation systems it would be desirable to know how rock properties influence breakage.The strength of rock is influenced by the environmental conditions imposed on the rock.Those of most importance in rock are (1)confining pressure ,(2)pore fluid pressure, (3)temperature and (4)rate of load application .Increase in confining pressure, as with increasing depth beneath th earths surface or under the action of a fragmentation tool, causes an increase in rock strength .Apparent rock strength decreases as porc fluid pressure increases, since it decreases the effect of confining pressure. Although chemical effects of pore fluids influence rock strength, they generally are small compared to the confining pressure effect, except for a small minority of rock types .Increase in rock temperature causes a decrease in rock strength.This effect is very small becaus