distinguish between open cast mining and shaft mining
Answers
(#) Open cast mining in which large pits are dug to excavate the ores lying at shallow depths beneath the surface of the earth. Minerals that lie near the surface are also dug out by the process of quarrying. ... Deep shaft mining in which deep holes are made to reach the ore lying at great depth beneath the crust.
Explanation:
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.
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 .
Open-pit, open-cast or open cut mining is a type of surface mining
Open-pit mines are used when deposits of commercially useful ore or rocks are found near the surface; that is, where the (surface material covering the valuable deposit) is relatively thin or the material of interest is structurally unsuitable for tunneling (as would be the case for sand, cinder, and gravel).
Open-pit mines that produce building materials and dimension stone are commonly referred to as "quarries."
Open-pit mines are typically enlarged until either the mineral resource is exhausted, or an increasing ratio of overburden to ore makes further mining uneconomic. When this occurs, the exhausted mines are sometimes converted to landfills for disposal of solid wastes
