Selasa, 30 September 2014


Deep beneath the surface of the earth lie some of the most frightening factories in the world: underground mines. Because surface mines become generally inefficient at depth greater than 60 meters, underground mines usually are used alternatively. Underground mines pose a greater safety risk and limit the size of equipment that can be used. For information, this kind of mine only is saw generally on uranium mining and gold mining.

When building an underground mine, we dig a tunnel to get to the minerals. This can be a straight vertical tunnel called a shaft or a tunnel that spirals gradually downwards, called decline. To access the ore from the shaft or decline, we dig other tunnels.We also mine out tunnels to provide proper ventilation and emergency exits.

We mine the tunnels and the ore bodies by drilling and blasting. The broken up ore is then transported to the surface for processing. Waste rock may be transported to the surface or left in the mine and used to fill empty space.

Once we remove all material inside the tunnels, we support them to make them safe. The type of ground support needed depends on how stable ground is and how long the tunnel is going to be used. These factors are identified in advance so that engineers can design the mine for maximum safety and value.

Ground support may be provided by rock bolts or split sets, which are forced into drilled holes to exert pressure on the surrounding rocks. Chemicals or grouts are sometimes added with rock bolts to give them a greater strength. We also install wire mash to stop smaller rocks from failing down.

High-pressure spaying of shotcrete (a mortar/concrete mix) onto the tunnels' walls and backs provides more support. As we complete mining in each stope, we backfill it with a cement mixture as well.


Due to its abundance, coal has been mined in various parts of the world throughout history and coal mining continues to be an important economic activity today. Compared to wood fuels, coal yields that have higher amount of energy per mass and can often be obtained in areas where wood is not readily available. Though historically used as a domestic fuel, coal is now mostly used in industry, especially in smelting and alloy production as well as electricity generation. Large-scale coal mining developed during the Industrial Revolution, and coal provided the main source of primary energy for industry and transportation in industrial areas from the 18th century to the 1950s. Coal remains an important energy source, due to its low cost and abundance when compared to other fuels, particularly for electricity generation. Coal is also mined today on a large scale by open pit methods wherever the coal strata strike the surface or are relatively shallow. Britain developed the main techniques of underground coal mining from the late 18th century onward with further progress being driven by 19th century and early 20th century progress. However, oil and its associated fuels began to be used as alternative from the 1860s onward. By the late 20th century coal was for the most part replaced in domestic as well as industrial and transportation usage by oil, natural gas, nuclear power, or renewable energy sources. By 2010, coal produced over a fourth of the world's energy, and by 2050 is expected to produce about one-third.

Source: Wikipedia