Hobbies And Interests
Function
Open pit mines are used when deposits of commercially useful minerals are found near the surface of the earth. It is also used when the material surrounding the minerals is structurally unsuitable for tunneling. For example, loose material such as sand and gravel.
Method
Open pit mines are dug on benches. The benches are dug in four to 60 meter intervals, depending on the machinery being used. These benches give the walls of an open pit mine a characteristic "stepped" appearance. The reason for digging a ̶0;stepped̶1; open pit is to prevent rock falls. In some situations the steps are even reinforced for extra stability. Reinforcement methods include shotcrete and rock bolts. To further enhance stability, de-water bores may be drilled into the steps to relieve water pressure. Water pressure in the rock can cause the material to lose its cohesion, and fail. A haul road is built at the side of the pit. The road is ramped so trucks can transport ore and waste rock out of the pit. The waste rock, also referred to as overburden, is the rock material that does not contain any minerals. A waste rock pile is built near the open pit. The waste rock pile is also tiered, for the same reasons as the open pit. Open pit mines are dug deeper until either the mineral resources is exhausted or until the proportions of overburden to ore make further mining uneconomic.
Economics
There are various factors involved in deciding whether or not an open pit mine is economically feasible. These include: the potential amount of the resource, how difficult it will be to extract the resource, the cost of environmental impact and the costs of reclamation.
Reclamation
After the resource is exhausted and mining stops, reclamation is required to get the disturbed area back in order. The steps involved in reclamation include stabilizing the waste damp, covering the waste materials with clay and soil to reduce the contact with the atmosphere. Contact with rain and oxygen can oxidize the sulfides in the exposed rock, which contributes to acid mine drainage. Vegetation is planted over the soil to increase the surface̵7;s stability. The open pit can be converted to a land fill or allowed to fill with groundwater.
Environmental Impact
Like all methods of mining, there are environmental implications to open pit mining. During mining, air quality, noise and vibrations can disrupt the local area. The process of open pit mining involves the loss of wild life habitat, loss of vegetation and alterations in water runoff. After mining is completed, subsidence can occur, and toxic chemicals can leach from left-over waste material. Before a government will approve a company̵7;s mining plans, the company has to show how they will mediate the environmental impacts. The rules and regulations regarding the management of the environmental implications of mining depend on the country where the mine is located. Generally speaking, developed countries have stricter regulations.