Introduction to surface mining


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Introduction to surface mining

  1. 1. Surface mining and underground mining
  2. 3. <ul><li>Surface mining </li></ul><ul><li>is a type of   mining   in which soil and rock overlying the mineral deposit ( the   overburden) are removed . </li></ul><ul><li>Surface mining is used when deposits of commercially useful minerals   or rock   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 (. </li></ul>
  3. 4. <ul><li>It is the opposite of underground mining , in which the overlying rock is left in place, and the mineral removed through shafts or tunnels . </li></ul><ul><li>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. </li></ul>
  4. 6. <ul><li>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 . </li></ul><ul><li>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 . </li></ul>
  5. 9. <ul><li>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 . </li></ul><ul><li>  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 . </li></ul>
  6. 10. <ul><li>Underground mining </li></ul>
  7. 11. Underground mining
  8. 12. <ul><li>Types of surface mining </li></ul><ul><li>&quot;Strip mining&quot; 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 practical when the ore body to be excavated is relatively near the surface.  </li></ul>
  9. 13. <ul><li>“ Open pit mining &quot; refers to a method of extracting   rock   or   minerals   from the earth through their removal from an open pit or   borrow . </li></ul><ul><li>&quot; Mountaintop removal mining &quot; ( MTR ) is a form of coal mining that uses explosives to blast &quot; overburden &quot; off the top of some Appalachian mountains . </li></ul>
  10. 15. <ul><li>“ Dredging &quot; 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 . </li></ul>
  11. 16. <ul><li>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 .   </li></ul><ul><li>Slope stability investigation, analysis ( including modeling ) , and design mitigation is typically completed by   geologists ,  engineering geologists , or   geotechnical engineers .  </li></ul>Slope Stability
  12. 17. <ul><li>If the forces available to resist movement are greater than the forces driving movement, the slope is considered stable . </li></ul><ul><li>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 . </li></ul>
  13. 19. Types of movement <ul><li>SLIDES </li></ul>
  14. 20. <ul><li>Falls </li></ul><ul><li>Rock fall </li></ul>