25. Определите значения выделенных слов по сходству их корней с кор­ нями соответствующих слов в русском языке:

metallic and non-metallic ore minerals; types of ore; the contact of the deposit with the country rock; rational methods of opening up a deposit; minimum cost of production; rate of extraction; potential ore body; general geological characteristics of an ore body; mining methods to be applied; draglines and earth-movers; blasting or separating portions of rock; millions of tons of iron ore per each mining enterprise

26. Прочитайте текст б. Назовите основные системы разработки рудных месторождений.

ТЕКСТЕ

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

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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