Explain the following methods of mining.
1) Open-cast Mining
2) Underground Mining
3) Shaft Mining
Answers
1) Open-pit mining, also known as open-cast or open cut mining, is a surface mining technique of extracting rock or minerals from the earth by their removal from an open-air pit, sometimes known as a borrow.
2) Underground hard rock mining refers to various underground mining techniques used to excavate hard minerals, usually those containing metals such as ore containing gold, silver, iron, copper, zinc, nickel, tin and lead, but also involves using the same techniques for excavating ores of gems such as diamonds or rubies.
3) Shaft mining or shaft sinking is excavating a vertical or near-vertical tunnel from the top down, where there is initially no access to the bottom. Shallow shafts, typically sunk for civil engineering projects, differ greatly in execution method from deep shafts, typically sunk for mining projects.
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1) Open-pit mining, also known as open-cast or open cut mining, is a surface mining technique of extracting rock or minerals from the earth by their removal from an open-air pit, sometimes known as a borrow. This form of mining differs from extractive methods that require tunnelling into the earth, such as long wall mining. Open-pit mines are used when deposits of commercially useful ore or rocks are found near the surface. It is applied to ore or rocks found at the surface because the overburden is relatively thin or the material of interest is structurally unsuitable for tunnelling (as would be the case for sand, cinder, and gravel). In contrast, minerals that have been found underground but are difficult to retrieve due to hard rock, can be reached using a form of underground mining.
To create an open-pit mine, the miners must determine the information of the ore that is underground. This is done through drilling of probe holes in the ground, then plotting each hole location on a map. The information gained through the holes with provide an idea of the vertical extent of the ore's body. This vertical information is then used to pit tentative locations of the benches that will occur in the mine.[2] It is important to consider the grade and economic value of the ore in the potential pit.[3] Open-pit mines that produce building materials and dimension stone are commonly referred to as "quarries."
2) Underground mining is used to extract ore from below the surface of the earth safely, economically and with as little waste as possible. The entry from the surface to an underground mine may be through a horizontal or vertical tunnel, known as an adit, shaft or decline.
Underground Mining Methods
• Cut and Fill Mining. In this selective mining method, the void created by mining is backfilled with a mixture of waste rock or tailings (with cement sometimes added to strengthen the mixture), which helps support the walls of the empty space.
• Shrinkage.
• Sublevel Longhole.
• Room & Pillar.
• Block Caving.
3) Shaft mining or shaft sinking is excavating a vertical or near-vertical tunnel from the top down, where there is initially no access to the bottom. Shallow shafts, typically sunk for civil engineering projects, differ greatly in execution method from deep shafts, typically sunk for mining projects. When the top of the excavation is the ground surface, it is referred to as a shaft; when the top of the excavation is underground, it is called a winze or a sub-shaft. Small shafts may be excavated upwards from within an existing mine as long as there is access at the bottom, in which case they are called Raises. A shaft may be either vertical or inclined (between 45 and 90 degrees to the horizontal), although most modern mine shafts are vertical. If access exists at the bottom of the proposed shaft and ground conditions allow then raise boring may be used to excavate the shaft from the bottom up, such shafts are called borehole shafts.