Gebirgsmechanische Aspekte des "Post Pillar" - Abbauverfahrens

Translated title of the contribution: Geomechanical aspects of the "post-pillar" mining method

Hannes Blaha

Research output: ThesisDoctoral Thesis

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Abstract

The „post pillar“ mining method is suitable for flat to middle steeply dipping mineral deposits with a limited extension. The “post pillar” mining system has a high degree of freedom regarding the adaptation of the deposit, both vertically and laterally. Because of the fact that the “post pillar” system is very flexible and the mining itself is carried out with the use of backfill from the bottom to the top of the deposit. This leads to very complex mining panel geometries. At the beginning of the mining process, the horizontal extension of the mining panel causes the formation of a stress arch above the panel, resulting in wide related pillar loads. During the slice by slice extraction of the deposit, the pillars in the backfill are getting slimmer, and due this geometric changes, the pillars are also getting softer - concerning their load-deformation behaviour. The load acting on the pillar reduces during the mining process and the pillars are getting higher. It was possible to demonstrate the influence of the width and the height of the mining panel on the load acting on the pillars within the “post pillar” system by using the “Hypothesis of Winkler” to complement and extend the numerical simulations. The investigations have shown that backfill has a greater impact on the strength of very slender and backfilled pillars than previously thought. Due to its areal effect backfill provides a high pressure resistance reaction against deformation. One of the key findings of the work are the results concerning the question of stability of the overall "post pillar" mining system. It could be shown, that the width of the “post pillar” panel is a key parameter for successful application of the mining method. The panel width influences the load acting on the pillar and the stability behaviour. Broader mining panels leads to greater loads on the pillar but also result in a more unstable situation overall. On the other hand, with increasing height of the mining panel the overall situation becomes more rigid and stable. This confirms the statement made at the beginning of the summary "suitable for deposits with limited expansion" as a key statement. The “post pillar” mining method is just so successful, because the relevant mining panel widths were held in all the examples from the literature rather small and the stability disadvantage of very slender pillars is compensated by the effects of the backfill and the stiff behaviour of the load system.
Translated title of the contributionGeomechanical aspects of the "post-pillar" mining method
Original languageGerman
QualificationDr.mont.
Supervisors/Advisors
  • Schubert, Wulf, Assessor B (external), External person
  • Wagner, Horst, Assessor A (internal)
Publication statusPublished - 2012

Bibliographical note

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Keywords

  • post-pillar
  • pillar
  • backfill
  • pillar strength
  • stability

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