爆破在岩巷掘进中的应用及井巷支护-毕业设计英文翻译

1、SHAFT AND DRIFT EXCAVATION BY BLASTING AND SHAFT SUPPORT1 APPLICATION OF BLASTING IN SHAFT AND DRIFT EXCAVATION1.1 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 fragm

2、ent 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

3、 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

4、 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 tempera

5、ture causes a decrease in rock strength.This effect is very small because of the small ambient temperature changes found during mining. An increase in rate of load application causes an apparent increase in rock strength.Rock exhibits directional properties that in fluence the way it breaks. These are embodied in the concept of rock fabric ,which connotes the structure or configuration of the aggregate components as well as the physical or mechanical property manifestations. Rock fabric ont only

6、 relates to the preferred orientation of mineral constituents and their planes of weakness, but also to the configuration of discontinuities, microcracks and pores.Joints and bedding planes have great influence on fragmentation at field scale.Physical properties of rock (density,indentation,hardness,abrasivehardness and porosity ,)are frequently used in conjunction with mechanical properties to develop better empirical esti mations of rock fragmentation.1.2 BLASTHOLE CHARGING METHODSDrill hole c

7、harging can be carried out in different ways depending on whether the explosive used is in cartridges or in the form of loose material. The oldest charging method implies the use of a tamping rod and this system is still used to a very great extent .During the last 20years, compressed air chargers have been used and these machines provide both good capacity and also an improved level of charge concentration so that the drill holes are utilized to a higher degree. During the last few years semi-a

8、utomatic chargers have been taken into use, primarily in underground work. Compressed air chargers for blasting powder in the form of loose material have also come into use on a large scale. As far as slurry blasting is concerned, special pumping methods have been developed through which charging capacity in the case of large diameter drill holes is practically good.A tamping rod must be made of wood or plastic. It must not be too thick in relation to the drill hole diameter since this can crush

9、 and damage fuse or electric detonator cables during charging work. If a good degree of packing is to be obtained during charging with a tamping rod then only one cartridge at a time should be charged and tamped. The detonator must be correctly fed into the drill hole during charging work.Compressed air chargers have been in use is Sweden for about 20 years. The first type consisted of aluminum pipes connected together and the cartridges were blown into the hole with an air pressure of 42 pounds per square inch .since that time the charging tube has been replaced by anti-static treated plastic hose of a special design. A charger includes a foot-operated valve, reduction vavle with air hose, breech, connecting tube and charging hose.The semi-automatic charger permits the continuous insertion of explosive cartridge at the same rate as they are charged in the hole by the hose .Instead of a valve being used ,the cartridges pass through an air lock between t

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