Correct Answer - Option 3 : Heating
Concept:
Quarrying:
- The process of raking out stones from natural rock beds is known as quarrying.
- In the case of a mine, the operations are carried out under the ground at great depth.
- In the case of the quarry, the operations are carried out at ground level in an exposed condition.
The methods of quarrying the stone are as follows:
(A) Blasting:
- In this method, explosives are used to convert rocks into small pieces of stones.
- This method is used when the stone to be excavated is of very hard variety and has no cracks or fissures.
- Moreover, if a stone is to be excavated on a very large scale, the blasting method will have to be adopted.
- After blasting, the excavated stone is sorted out into different sizes and categories.
- Explosives such as blasting powder, blasting cotton, dynamite, and cordite are used.
The operations involved are as follows:
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Boring - The process of making holes are drilled or bored in the rock.
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Charging - The holes arc dried completely and the required amount of charge is placed in the holes.
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Tamping - After placing the charge in the hole, a greased priming needle, projecting a little outside the hole, is placed in the hole which is then filled up with damp clay or stone dust in layers tamped sufficiently with a braced tamping rod.
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Fining - Blasting powder and cordite are ignited by means of a fuse, whereas gun cotton and dynamite are exploded by detonation.
(B) Digging or Excavating:
- Stones buried in the earth or under loose overburden are excavated with pickaxes, crowbars, chisels, hammers, etc.
(C) Heating:
- Heating is most suitable for quarrying small, thin, and regular blocks of stones from rocks, such as granite and gneiss.
- A heap of fuel is piled and Fred on the surface of the rock in a small area.
- The two consecutive layers of the rocks separate because of the uneven expansion of the two layers.
- The loosened rock portions arc broken into pieces of the desired size and are removed with the help of pick-axes and crowbars.
- Stone blocks so obtained are very suitable for coarse rubble masonry.
(D) Wedging:
- This method is mainly used for the rock of sedimentary type, which is comparatively soft, such as sandstone, limestone, marble, slate, laterite.
- In this method, first of all naturally occurring cracks or fissures are located in the rocks, to be excavated.
- The steel wedges or points are then driven with the help of a hammer, in hammer fissures or cracks and stones are detached.
- The split-out blocks of stone can be converted into marketable forms and supplied to users.
(E) Channeling Machines:
- In this method, the channeling machines are driven by steam, compressed air, or electricity are used to make vertical or oblique grooves or channels on the rock mass and make rapidly the grooves.
- This process of separation of stone from the rock mass is almost invariably employed in the case of limestones, marbles, and other soft sandstones.
- It is possible to separate very large blocks of stones from the rocks by the application of this method.
