For on to in between for on into as into

1. A mine shaft is frequently split … multiple compartments. 2. … this reason, explosives with excellent water resistance properties are preferred. 3. The time-consuming cleaning of the floor … the blasts can be minimized. 4. The second reason to divide the shaft is … ventilation. 5. The plenum or casing, is incorporated … the headframe. 6. The design of the cross section of the shaft principally depends … the quality of the rock. 7. An additional compartment houses mine services such … high voltage cables and pipes. 8. … mining, they form a system of vertically or inclined passageways. 9. … the surface above the shaft stands a building known as the headframe. 10. Furthermore, the drilling and blasting crews are exposed …falling objects.

14. Fill in the articles if necessary:

1. Larger shafts are round and are … concrete lined. 2. … explosives used in shaft sinking must always be water-resistant.3. Shaft sinking is one of … most difficult and risky blasting jobs. 4. … top of the excavation is the ground surface. 5. … largest compartment is typically used for the mine cage. 6. … second compartment is used for one or more skips. 7. A mine shaft is frequently split into … multiple compartments. 8. … third compartment is used for an emergency exit. 9. It is also easy to keep the shaft free from … water. 10. On … surface above the shaft stands a building known as the headframe.

15. A three-minute talk. Discuss these questions with your groupmates:

a) the choice of explosives;

B) blasting methods.

Complete a project: “The deepest shafts”.

SUPLEMENTARY READING

Mine Development

Rock and Minerals

High temperatures and chemical reactions are some of the processes behind the concentrations of metal bearing minerals, found in the bedrock of the earth crust.

A rough classification divides rock into sedimentary, metamorphic and igneous. Igneous rock, created by volcanic forces and high temperatures, is generally compact and massive in structure. Rapidly cooled lava flows harden into massive, homogenous rock. Granite, formed deep inside the earth's crust, has cooled more slowly, developing crystalline patterns, with aggregates of quartz, feldspar and mica.

Sedimentary rocks are created by erosion, with fragments carried by water streams settling at the sea bottom, and left for millions of years to consolidate into a solid mass. Sedimentary rocks are identified by stratification, with younger rocks layered on top of older formations.

Metamorphic rocks were originally sedimentary or igneous formations, and later restructured by heat and/or pressure. The origin of metamorphic rocks can be difficult to detect. Nevertheless, despite their origin, all of these rock types have to be drilled efficiently, which is where Atlas Copco experience in mechanized rock excavation really counts.

Ores and Orebodies

Ore is an economic concept, defined as a concentration of minerals, which can be economically exploited and turned into a saleable product.

Before a mineral prospect can be labelled as an orebody, full knowledge is required about the mineralization, proposed mining technology and processing.The feasibility study has to be undertaken to prove that the prospect can be economically developed into a mine.

Metal prices set on the London Metal Exchange (LME) determine the day-to-day value of a mine's ore.

Run-of-mine ore is treated in a dressing plant, and processed into different concentrates. Where the ore contains more than one metal of value, separate concentrates of various minerals are produced. The value of in-situ ore can be calculated by applying market prices to metal contents, and deducting costs for treatment and transportation of concentrates, together with the smelter's fee. The balance should cover the direct mining costs, and leave a margin for the mine operator.

Metal prices fluctuate from day to day, depending on the supply-demand situation. An oversupply builds stocks of surplus metal, and the market price drops, along with the profit margin. As costs for processing, transport, smelting and refining remain constant the mine takes the squeeze of reduce income. The mine operating on narrow margin must prepare to survive periods of depressed metal prices.

One tactic is to adjust ore boundaries to a higher cut-off grade to increase the value of the run-of-mine product. Another is to increase the efficiency of mine production by modifying the mining method, possibly by introducing new, more powerful machines. The mine must remain profit generator, in an environment of increasing manpower cost and demand for better quality of life.

Date: 2015-12-24; view: 575