Surface mining and Surface mining and underground miningunderground mining

Surface miningSurface mining is a type ofis a type of  miningmining  in which soil and rock in which soil and rock

overlying the mineral deposit overlying the mineral deposit ((thethe  overburden)overburden) are removedare removed. .

Surface mining is used when deposits of Surface mining is used when deposits of commercially usefulcommercially useful mineralsminerals  or rockor rock  are are found near the surface; that is, where the found near the surface; that is, where the overburden is relatively thin or the overburden is relatively thin or the material of interest is structurally material of interest is structurally unsuitable for tunneling unsuitable for tunneling ((as would usually as would usually be the case forbe the case for  sandsand, , andand  gravelgravel (.(.

It is the opposite of underground miningIt is the opposite of underground mining, , in which the overlying rock is left in place, in which the overlying rock is left in place, and the mineral removed through shafts and the mineral removed through shafts or tunnelsor tunnels..

In most forms of surface mining, heavy In most forms of surface mining, heavy equipment, such as equipment, such as earthmoversearthmovers, first , first remove the overburden. Next, huge remove the overburden. Next, huge machines, such as machines, such as dragline excavatorsdragline excavators or  or Bucket wheel excavatorsBucket wheel excavators, extract the , extract the mineral. mineral.

Where minerals occur deep below the Where minerals occur deep below the surface—where the overburden is thick or surface—where the overburden is thick or the mineral occurs as veins in hard rock— the mineral occurs as veins in hard rock— underground mining methods are used to underground mining methods are used to extract the valued materialextract the valued material. . Surface mines are typically enlarged until Surface mines are typically enlarged until either the mineral deposit is exhausted, or either the mineral deposit is exhausted, or the cost of removing larger volumes of the cost of removing larger volumes of overburden makes further mining no longer overburden makes further mining no longer economically viableeconomically viable. .

In open-pit mining a Stripping Ratio refers to the amount of waste rock removed to recover ore. For example, a stripping ratio of 3:1 means to recover one ton of ore you must remove three tons of waste rock.

 A large Stripping Ratio is less economical efficient than a small one, because that means more rock will need to be moved without generating revenue. If The ratio is going to be too large, then underground mining will usually be more efficient.

•Underground miningUnderground mining

Underground mining

Types of surface miningTypes of surface mining"Strip mining""Strip mining" is the practice of mining a is the practice of mining a

seam of mineral by first removing a long seam of mineral by first removing a long strip of overlying soil and rock (the strip of overlying soil and rock (the overburdenoverburden). It is most commonly used to ). It is most commonly used to mine mine coalcoal or  or tar sandtar sand. Strip mining is only . Strip mining is only practical when the ore body to be practical when the ore body to be excavated is relatively near the surface.  excavated is relatively near the surface. 

““Open pit miningOpen pit mining" refers to a method of extracting rock or minerals from the earth through their removal from an open pit or borrow.

"Mountaintop removal mining" (MTR) is a form of coal mining that uses explosives to blast "overburden" off the top of some Appalachian mountains.

“Dredging" is a method often used to bring up underwater mineral deposits. Although dredging is usually employed to clear or enlarge waterways for boats, it can also recover significant amounts of underwater minerals relatively efficiently and cheaply.

The field ofThe field of  slope stabilityslope stability  encompasses the encompasses the analysis of static and dynamic stability of analysis of static and dynamic stability of slopes of earth and rockslopes of earth and rock--fill dams, slopes of fill dams, slopes of other types of embankments, excavated other types of embankments, excavated slopes, and natural slopes in soil and soft rockslopes, and natural slopes in soil and soft rock..  

Slope stability investigation, analysis Slope stability investigation, analysis ((including including modelingmodeling)), and design mitigation is typically , and design mitigation is typically completed bycompleted by  geologistsgeologists, , engineering engineering geologistsgeologists, , oror  geotechnical engineersgeotechnical engineers.  . 

Slope Stability

If the forces available to resist movement are greater than the forces driving movement, the slope is considered stable.

A factor of safety is calculated by dividing the forces resisting movement by the forces driving movement. In earthquake-prone areas, the analysis is typically run for static conditions and pseudo-static conditions, where the seismic forces from an earthquake are assumed to add static loads to the analysis.

Types of movement

SLIDES

Falls Rock fall