Civil Engineering Chapter 10: Underground Mining Methods
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Questions and Answers

What is the primary consideration when determining room sizes and pillar dimensions in room and pillar mining?

  • Rock conditions and predicted rock stress changes (correct)
  • Maximizing ore recovery
  • Drill and blast technique used
  • Minimizing operating costs

    • What is the characteristic of ore bodies suitable for sublevel open stoping?

  • Steep dip and irregular shape
  • Shallow dip and undefined ore boundaries
  • Shallow dip and regular shape
  • Steep dip, regular shape, and defined ore boundaries (correct)

    • What is the purpose of stabilized fill in primary stopes?

  • To prevent sidewalls from caving in when secondary stopes are mined (correct)
  • To provide additional support to pillars
  • To reduce operating costs in primary stopes
  • To increase ore recovery in primary stopes

    • What is the sequence of mining in sublevel open stoping?

    <p>Primary stopes are mined first, and secondary stopes are left as pillars</p> Signup and view all the answers

    What is the main advantage of sublevel open stoping?

    <p>Increased productivity and multiple production points</p> Signup and view all the answers

    What is critical to the success of room and pillar mining?

    <p>Establishing the optimum sizes of the rooms and pillars</p> Signup and view all the answers

    What is the purpose of pillars in room and pillar mining?

    <p>To support the overhead rock mass</p> Signup and view all the answers

    What is the common mining method used for ore bodies with a dip less than 50 degrees?

    <p>Room and pillar mining</p> Signup and view all the answers

    What is the primary purpose of installing cable bolts above the stope?

    <p>To provide additional support to the rock mass</p> Signup and view all the answers

    What percentage of freshly broken ore is typically drawn from the base of the stope after each blast in shrinkage stoping?

    <p>30-35%</p> Signup and view all the answers

    What is a characteristic of orebodies that are suitable for shrinkage stoping?

    <p>They have no tendency for oxidation, hydrolysis, dissolution, or development of cementitious materials</p> Signup and view all the answers

    What is the main disadvantage of shrinkage stoping in terms of production scheduling?

    <p>Only 30-35% of the freshly broken ore is drawn from the base of the stope after each blast</p> Signup and view all the answers

    What is the primary focus of describing rock mass response to stoping activity?

    <p>Analyzing the displacement of orebody peripheral rock induced by mining</p> Signup and view all the answers

    What is the purpose of backfilling in mining?

    <p>To reuse waste for backfill material</p> Signup and view all the answers

    What is the primary difference between shrinkage stoping and VCR stoping?

    <p>VCR stoping uses larger diameter drilling</p> Signup and view all the answers

    What is the main purpose of the Room and Pillar method in underground mining?

    <p>To create a system of open rooms and pillars for support</p> Signup and view all the answers

    Which underground mining method involves the use of artificial support, such as shrinkage stoping and VCR stoping?

    <p>Artificial Support Techniques</p> Signup and view all the answers

    What is the progression direction of VCR stoping?

    <p>Vertical</p> Signup and view all the answers

    What is a characteristic of shrinkage stoping?

    <p>Most of the blasted ore remains in the stope to support the hanging wall and footwall</p> Signup and view all the answers

    What is the primary characteristic of the Cut-and-Fill Stoping method?

    <p>It uses a series of horizontal slices to extract ore</p> Signup and view all the answers

    Which underground mining method is characterized by the extraction of ore in large blocks or panels?

    <p>Block Caving</p> Signup and view all the answers

    What is the primary purpose of the Sublevel Open Stoping method?

    <p>To extract ore from large orebodies</p> Signup and view all the answers

    Which underground mining method is used for mining orebodies that are too deep or too large for other methods?

    <p>Block Caving</p> Signup and view all the answers

    What is the primary difference between Pillar-supported methods and Unsupported methods?

    <p>The use of artificial support techniques</p> Signup and view all the answers

    What is the primary characteristic of caving methods in mining?

    <p>Induced, controlled, massive caving of the ore body or overlying rock</p> Signup and view all the answers

    Which type of orebodies is block caving typically used for?

    <p>Weak and massive orebodies</p> Signup and view all the answers

    What is the primary advantage of block caving?

    <p>High production rates at relatively low cost</p> Signup and view all the answers

    What is the minimum height requirement for orebodies to be suitable for block caving?

    <p>100 m</p> Signup and view all the answers

    What process occurs when temporary pillars in an undercut excavation are removed?

    <p>Failure and progressive collapse of the undercut crown</p> Signup and view all the answers

    What is the most favorable rock structural condition for caving?

    <p>At least two prominent subvertical joint sets with subhorizontal</p> Signup and view all the answers

    What is the primary characteristic of sublevel caving?

    <p>Used in strong and massive orebodies with weak host rock</p> Signup and view all the answers

    What is the result of inducing free displacement of the country rock overlying an orebody in sublevel caving?

    <p>Caving of the host rock into the void</p> Signup and view all the answers

    What is the primary advantage of using long and subvertical blast holes in mining?

    <p>Elimination of the need for entry of operating personnel into the developing mine void</p> Signup and view all the answers

    What is the typical sequence of operations in Cut and Fill Stoping?

    <p>Drilling &amp; blas]ng → scaling &amp; support → ore loading &amp; transport → backfilling</p> Signup and view all the answers

    What is the typical range of stope spans in Cut and Fill Stoping?

    <p>4 ~ 40 m</p> Signup and view all the answers

    What is the primary advantage of Cut and Fill Stoping in terms of environmental benefits?

    <p>Limited possibility of surface subsidence</p> Signup and view all the answers

    What type of orebodies is Cut and Fill Stoping typically applied to?

    <p>All of the above</p> Signup and view all the answers

    What is the primary characteristic of Bench and Fill Stoping?

    <p>It is a more productive alternative to cut-and-fill method</p> Signup and view all the answers

    What is the initial step in Bench and Fill Stoping?

    <p>Drilling and extraction drives along the ore length and width</p> Signup and view all the answers

    What is the main reason why Cut and Fill Stoping is suitable for low rock mass strength conditions?

    <p>Because it provides better control of rock performance</p> Signup and view all the answers

    Study Notes

    Rock Mass Response to Stopping Activity

    • The performance of the host rock mass during mining activity is described in terms of the displacements of orebody peripheral rock induced by mining.

    Pillar Supported Methods

    • Room and Pillar:
      • A common mining method for ore bodies with a dip less than 50 degrees.
      • A grid system of open rooms and pillars to support the overhead rock mass is created.
      • The mining sequence can be optimized to accommodate rock conditions and ventilation demands.
      • The ore is usually mined out using the same drill and blast technique as in conventional drilling.
    • Sublevel Open Stoping:
      • A commonly used method in large-scale mining.
      • Enables multiple production points in operation at the same time, offering good productivity.
      • Used for large ore bodies with a steep dip, regular shape, and defined ore boundaries.
      • Drills are created through the ore body to enable mining of stopes between sublevels.

    Artificial Support Techniques

    • Shrinkage Stoping:
      • A vertical stoping method conducted in a vertical or near-vertical plane.
      • Most of the blasted ore remains in the stope to support the hanging wall and footwall.
      • Applied to vertical or subvertical advance of mining in a stope.
      • Broken ore is used as both a working platform and temporary support.
    • VCR Stoping (Vertical Retreat Stoping):
      • A configuration method in stopes where drilling large diameter is used to detonate horizontal slices of ore.
      • The method progresses vertically, as successive slices are blasted.
      • Applied to cases where conventional shrink stoping is feasible, but narrow orebody width may not be tractable.
    • Cut and Fill Stoping:
      • A method where a portion of the stope is mined, and then completely backfilled with broken rock or a mix of cement and waste rock.
      • Mostly mining proceeds up-dip in an inclined orebody.
      • Drilling and blasting are done about 3m thick, followed by scaling and support, ore loading and transport, and backfilling.
      • Applied in veins, inclined (35°-90°) tabular orebodies, and massive deposits.
    • Bench and Fill Stoping:
      • Developed in the early 1990s as a more productive alternative to cut-and-fill method.
      • Initially, drilling and extraction drives are mined along the ore length and width.
      • A bench slot is created between these two horizons at the end of the orebody.

    Unsupported Methods

    • Block Caving:
      • A method used in weak and massive orebodies, where the ore is undercut, and then the remainder of the orebody collapses into the void created.
      • The host rock is fairly strong, although ultimately it tends to cave into the void created from removing the ore.
      • A kind of mass mining method with high production rates at relatively low cost.
      • Applicable only to large orebodies with a height of more than 100m which have a fairly uniform distribution of grade.
    • Sublevel Caving:
      • A type of caving used in strong and massive orebodies in which the host rock is very weak and quickly caves into the void created by removing the core.
      • As in block caving, the cave will ultimately reach the surface.
      • Induces free displacement of the country rock overlying an orebody.
      • Ore and waste are fragmented using blast holes drilled upwards from headings.
      • Sublevel caving and block caving have application to inclined or vertical, massive deposits, almost exclusively metallic or nonmetallic.

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    Description

    This quiz covers the concepts and principles of underground mining methods and related rock mechanics considerations, as discussed in Chapter 10 of a Civil Engineering course.

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