采礦專業(yè)外文翻譯-wenkub
2022-12-17 01:44:27 本頁面
【正文】 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 pared to the confining pressure effect, except for a small minority of rock types .Increase in rock temperature causes a decrease in rock 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 ponents as well as the physical or mechanical property 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 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. 2 BLASTHOLE CHARGING METHODS Drill hole charging 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, pressed 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 semiautomatic chargers have been taken into use, primarily in underground work. Compressed air chargers for blasting powder in the form of loose material have also e 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 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 antistatic treated plastic hose of a special design. A charger includes a footoperated valve, reduction vavle with air hose, breech, connecting tube and charging hose. The semiautomatic 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 two fla
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