Opencast Mining in India

Opencast Mining or quarrying by manual methods is adopted,

where large investment is not warranted,
where mechanization is likely to prove inefficient, either due to large size of pits or to the shape of the pits, and their location,
where mineralization is erratic and where selective mining with sorting is called for, thus inhabiting the use of mechanical mining, and
where large-scale work is possible with cheap labor.
A general pattern of the lay-out for open casting, whether it is below ground level or above ground level, is to form benches or stepped working-faces.

Opencast mining in India is practiced in manganese-ore mining in Madhya Pradesh and the overburden benches are 30 ft (9 meters) high. Blast-hole drilling is employed and power shovels are used for loading into the dumpers or trucks. Bulldozers do the leveling of the waste.

Waste disposal is a serious problem, as the ratio of overburden to ore is very high, especially in Maharashtra and Madhya Pradesh.

In the iron-ore mines of Singhbhum (Bihar), e.g., Noamundi, blast-hole drilling is done to break vast quantities of ore, by using liquid-oxygen explosive.

Working in the Kargali coal-seam (Bokaro coalfield), one of the thickest seams in India, are mainly of the opencast type. Blast-hole drilling is practiced here and the loading is done into railway wagon, brought right into the quarry.

GLORY HOLE

In the glory hole method, the pit or quarry is opened up and developed in such a way, that the working faces are arranged in the form of concentric steps, descending to the deepest or central portion. Glory hole is a cheap method of mining and loading ore.

STRIP MINING

This method has been many used for winning coal. It is also a specialized method of opencast mining. It is being efficiently applied to extract coal seams, which occur under relatively-shallow cover, to yield a large output.