Difference between revisions of "Pillar design"

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(2.3 Potential Pillar Failure Modes)
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Revision as of 15:23, 4 February 2015

1.0 Classification of Pillars

1.1 Support Pillars

Support pillars are load carrying. Examples of support pillars include:

Type of Pillar Description
Sill Pillar Horizontal pillars that separate levels or stopes, often used when multiple levels are mined concurrently.
Room and Pillars Pillars are left in place in a predetermined and calculated pattern as rooms are mined out.
Yield Pillars Pillars are designed to fail by going past peak load carrying capacity. Roof-strata is maintained by relieving pressure in working areas and controlling transference of load to abutments that are clear of working areas and road ways.Yielded pillars still carry load.
Post Pillars Room and pillar variation where ore is mined out in a series of horizontal slices.
Barrier Pillars Solid blocks left between two mines or sections of a mine. Provides regional support in large mines to prevent accidents due to inrushes of water, gas, or explosions or a mine fire.
Bracket Pillars Slip on discontinuities may cause rockburst within stopes, which can cause equipment damageand injury or loss of life. Ore immediately adjacent to these geological structures is left unmined to protect the structure from mining induced stresses.

1.2 Protection pillars

Protection pillars provide shelter in a mine. Examples of protection pillars include:

Type of Pillar Description
Shaft Pillars A large area that is left unworked around the shaft bottom to protect the shaft and the surface building from damage due to subsidence . Protects the shaft itself.
Crown Pillars A rock mass of variable geometry, mineralized or not, situated above an uppermost stope of the mine, which serves to permanently or temporarily ensure the stability of surface elements. Surface elements include bodies of water, soil and precipitation . Separate underground from surface mining.
Boundary Pillars Pillars left in mines between adjoining properties . Usually formed between mines.
Barrier Pillars Large pillar left unworked between two mines for security against accidents arising from an influx of water .
Bracket Pillars Slip on discontinuities may cause rockbursts within stopes, which can cause equipment damage and injury or loss of life. The most practical measure to counteract these effects involve leaving left over strips of unmined ground adjacent to the features to reduce potential for them to slip .


2.0 General Aspects of Pillars

2.1 Pillar design considerations

Pillar design considerations that need to be taken into account include :

  • Pillar load
  • Strength of pillars (failure criteria)
  • Orebody geometry
  • Geological characteristics of a mine
  • Load-deformation characteristics of the pillar and stiffness of the loading system


2.2 Pillar design basics

Pillar design basics are mainly concerned with:

  • Peak-pillar strength (load-bearing capacity)
  • Post-peak or load-deformation characteristics of a pillar

Pillar load and load distribution need to be established and potential failure models must be always kept in mind.


2.3 Potential Pillar Failure Modes

The strength of pillars are highly dependent on the geological conditions of the mine and there is no universal pillar design method. The following pictures show the potential failure modes that need to be considered for pillar design which are spalling (hourglassing), shear fracturing (geology and stress), bulking/bulging (geology) and foundation failure:


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Please add a link to this page in the article that already exists on room and pillar mining.