State of the art of backfill technology in underground mining excavations

Anja Moser

Research output: ThesisMaster's Thesis

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Abstract

When the in-situ stress state far exceeds the compressive strength of the rock mass, the maximum extraction possible from a deposit may be unacceptably low. Therefore artificial support has to be applied, which has to control mine-near displacements and local stability as well. The most widely used artificial support is backfill, which is placed in openings underground. Today in most underground mines in Austria backfill represents an important part of the mining activities. The main reason for implementation of backfill in these mines is the need to stabilize the underground openings. Backfill should though not be considered as disposal of waste, but as reutilization, as benefits are taken from its application. So the overall goal of this work is to describe the role of backfill as essential part of mining activities and to conduct a review over different application fields of backfill. As several authors highlighted the importance of the influence of binding agent addition, a certain attention is contributed to cemented fill masses. Binding agents can be added to the fill product to reach the required physical and chemical properties, whereby the most used binding agent is Portland cement. During this work a look at different backfill classification systems is taken which are predominantly based on the material for backfill production, the backfill production and delivery methods. According to the literature, generally rock fill, hydraulic fill and paste fill are the most frequently used types of backfill. Further on the review of different bibliography about backfill showed the importance of backfill not just for stability reasons, but also for mine ventilation, climatization, as waste disposal, for higher selectivity and to avoid transportation. In underground mining, backfill is applied in supported mining methods, generally called cut and fill mining methods. Filling of underground openings in combination with pillars plays an important role as well, as the strength of pillars, their post-failure strength and their failure behavior are positively influenced. During this work it was observed that several properties can influence the performance of backfill, according to its specified application purpose. The main influencing parameters are the mineralogical composition, the particle size distribution and uniformity index, the addition of binding agents and additives, the addition of water and accordingly the water:cement ratio. Different laboratory testing methods to control the important properties were investigated and discussed during this work. Over all it was concluded that backfill represents an important part of mining activities. Several deposits could not be mined without backfill application and safety of works is increased as well. An important point to consider is that every backfill system is different due to different application purposes of backfill, which makes it difficult to design a general regulatory for backfill. However, some important questions like backfill application in high-productive mining methods and backfilling and mining activities as concurrent activities were not discussed in this work and require further investigations.
Translated title of the contributionStand der Technik der Versatztechnologie im untertägigen Bergbau
Original languageEnglish
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Wagner, Horst, Supervisor (internal)
Award date27 Mar 2015
Publication statusPublished - 2015

Bibliographical note

embargoed until null

Keywords

  • backfill
  • underground mining
  • cemented backfill
  • binding agents

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