7. Surface mining
• It is a type of mining in which soil and rock
overlying the mineral deposit
(the overburden) are removed.
• Surface mining is used when deposits of
commercially useful minerals or rocks are
found near the surface; that is, where the
overburden is relatively thin or the material of
interest is structurally unsuitable for tunneling
(as would usually be the case for sand ,
and gravel.(
8. • It is the opposite of underground mining ,in which
the overlying rock is left in place, and the mineral
removed through shafts or tunnels.
• In most forms of surface mining, heavy equipment,
such as earthmovers, first remove the overburden.
Next, huge machines, such as dragline
excavators or Bucket wheel excavators, extract the
mineral.
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32. • The field of slope stability encompasses the
analysis of static and dynamic stability of slopes of
earth and rock-fill dams, slopes of other types of
embankments, excavated slopes, and natural slopes
in soil and soft rock .
• Slope stability investigation, analysis (including
modeling), and design mitigation is typically
completed by geologists ,engineering geologists ,
or geotechnical engineers .
Slope Stability
33. • 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 .
45. • 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 economically 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 .
46. Where minerals occur deep below the
surface—where the overburden is thick or
the mineral occurs as veins in hard rock—
underground mining methods are used to
extract the valued material.
Surface mines are typically enlarged until
either the mineral deposit is exhausted, or
the cost of removing larger volumes of
overburden makes further mining no longer
economically viable .
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48. Problem-4:
Calculate the value of stripping ratio, if a mining company says that
during the year 5.4 million tons of material was mined and that the
mill processed was 2.1 million tons.
49. • “Open 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.
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55. Types of surface mining
"Strip mining“
• It is the practice of mining a seam of mineral by
first removing a long strip of overlying soil and rock
(the overburden).
• It is most commonly used to mine coal or tar sand.
Strip mining is only practicable when the ore body
to be excavated is relatively near the surface.
