采矿工程毕业设计翻译---爆破在井巷掘进中的应用

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1、 附录 外文翻译 APPLICATION OF BLASTING IN DRIVING TUNNEL 1 FRAGMENTATION Fragmentation 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 handli

2、ng 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)fri

3、ction (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 hi

4、ghly 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

5、 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 incr

6、easing 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 str

7、ength, 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 because of the small ambient temperature changes found during mining. An increase in rate of

8、 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 pr

9、operty manifestations. Rock fabric ont only 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 prop

10、erties 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. 2 BLASTHOLE CHARGING METHODS Drill hole charging can be carried out in different ways depending o

11、n 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 capac

12、ity 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-automatic chargers have been taken into use, primarily in underground work. Compressed air chargers for blasting powder in the form of loose material have al

13、so 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

14、 the drill hole diameter since this can crush 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 t

15、he 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 ha

16、s 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

17、 charged in the hole by the hose .Instead of a valve being used ,the cartridges pass through an air lock between two flaps. The air pressure in the charging hose is retained while cartridges are pressure in the charging hose is retained while cartridges are beins inserted .The semi-automatic charger

18、 permits considerably higher charging capacity than the normal type of charger. Explosives in the form of the form of loose material, usually ammonium nitrate explosives(ANFO), require special chargers. Two types can be differentiated: pressrure vessel machines and ejector units. Pressure vessel mac

19、hines are particularly suitable for crystalline An explosives with good charging capacity. Ejector units are operate by an ejector sucking up explosive from a container through a charging hose. The explosive is then blown through the charging hose into the drill hole .There are, also combined pressu

20、re ejector machines. The charging hose used for ANFO charging operations must conduct electricity and have a resistance of at least 1K/m and max.30K/M. Nitro Nobel has developed a special pumping procedure which consists of a tanker vehicle which is used to pump explosive directly the drill holes. T

21、he charging capacity is very high in the case of large diameter drill holes. 3 CONTROLLED BLASTING TECHNIQUTES Controlled blasting is used to reduce overbreak and minimize fracturing of the rock at the boundary of an excavation. The four basic controlled blasting techniques are: line drilling, presplitting, cushion blasting and smooth blasting. Line drilling, the earliest controlled blasting technique, involves drilling a row of closely spaced holes along the final excavation line, providing a plane of weakness to