Ore Mining
As has already been said mining is a branch of industry which deals with the recovery of valuable minerals from the interior of the Earth. When minerals occur so that they can be worked at a profit, they are called ore deposits. Economic minerals are those which are of economic importance and include both metallic (ore minerals) and non- metallic minerals such as building materials (sand, stone, etc.). In choosing the methods of working ore deposits one must take into consideration the following main factors: 1) the shape of the deposit; 2) the dimensions of the deposit in thickness, along the strike and down the dip; 3) the type of ore and the distribution of metal in the ore body. The shape of the ore deposit affects the mining method. Besides, the contact of the deposit with the country rock is of great importance. According to their angle of dip the deposits are divided into gently sloping (up to 25'), inclined (25-45*) and steep deposits (45-90*). The thickness of ore deposits also varies. They may be very thin (from 0.7-0.8 m to 20 m) and extremely thick (more than 20 m). One must say that a rational method of mining ensures the following: 1) safety; 2) minimum cost of production; 3) minimum losses of ore; 4) rate of extraction. In metal mining as well as in mining bedded deposits preliminary activities (before mining) involve prospecting and Unit 9
exploration required to locate, characterize and prove a potential ore body. After exploration has provided information on the shape and size of a deposit and its general geological characteristics, site development for mining begins. Mine development depends largely upon the kind of ore body and the mining method to be applied. As a rule mine development work involves development drilling; access road construction; clearing and grubbing; adit, slope or shaft development; overburden removal, construction of facilities such as concentration (dressing, processing) plants, etc. The different type of equipment required range from small, simple units such as backhoes and dump trucks to earth-movers, draglines and power shovels. Mining operations begin with excavation work (blasting or separating portions of rock from the solid mass), loading, hauling and hoisting of the rock to the surface and supporting mine workings. Generally speaking, the working of an ore deposit involves opening up, development, blocking out and sloping operations, the basic sloping methods in use now being open sloping, room and pillar mining, shrinkage sloping, block caving and others. After ores are mined or dredged, they are usually processed (crushed, concentrated or dried). Extraction processes can be done by underground or open-cast mining. The main trend has been toward low-cost open-cast mining. УПРАЖНЕНИЯ Укажите, какие предложения соответствуют содержанию текста. Подтвердите свои ответы фактами из текста. 1. Ore deposits may be called economically workable natural 2. It is quite enough to take into consideration the shape of the 3. The thickness of ore deposits is a constant value. 4. As a rule exploration provides information for mining. 5. Equipment of various types and capacities is readily available 6. After mining or dredging ores are usually processed, crushed Unit 9_____________________________________________ 231 28. Ответьте на следующие вопросы: 1. What minerals do we usually call economic? 2. Is the type of ore the only factor which the engineer takes into 3. What does a rational method of mining guarantee? 4. What does before mining activity include? 5. What processes does development work involve? 6. What basic sloping methods are in use now? 7. What are the main methods of working bedded deposits? 8. Is underground or open-cast mining preferable now? Why? 9. Can you give a few examples of the largest enterprises 29. Найдите в правой колонке русские эквиваленты следующих слов и со
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