Chapter 11: Coal Combustion Products in Mine Backfill Applications


Colin Ward, UNSW
David French, CSIRO Energy Technology, North Ryde, NSW
Jerzy Jankowski, UNSW
Harry Brown, Consultant Geoglist, Loftus, NSW
Ken Riley, Formerly CSIRO Energy Technology, North Ryde, NSW
Leanne Stephenson, UNSW
Zhongsheng Li, UNSW


The extraction of coal and other mineral resources inherently results in the creation of mining-induced voids that need to be managed in some way. Placement of backfill may be used to assist in managing these voids, with associated benefits to the stability, safety, resource recovery and environmental impact of the mining operation. Mine operators are under increasing obligations to remediate mine sites, to reduce future impacts and return the land for other uses. The use of coal combustion products as a backfilling material may provide a mechanism for reducing the impact of mining, as well as the cost of remediating these sites. Backfilling may also be integrated with the mining process, to improve stability and possibly increase recovery of the in situ resources.

Ash is one of many materials that may be used as a component of mine backfill (Potvin et al. 2005), whether for purposes such as stability improvement, subsidence control or mine-site rehabilitation. CCPs have a number of advantages for use as backfill in coal or metalliferous mining, whether used alone or in conjunction with other fill components. These include cementitious or pozzolanic characteristics, a capacity for placement in flowable paste or slurry form and availability in large quantities near many mine sites. CCPs may also have chemical properties that can be used to ameliorate other mine-related problems, such as the generation and discharge of acid waters from particular mining operations.


  1. 11.1 Overview of Ash Use in Mine Environments
  2. 11.2 Regulatory Framework and Information Requirements
    1. 11.2.1 Relevant authorities in Australia
    2. 11.2.2 Issues to be addressed
    3. 11.2.3 Regulatory framework across major developed economies
    4. 11.2.4 Potential Impacts of ash placement at mine sites
    5. 11.2.5 Evaluation and monitoring requirements
  3. 11.3 Ash Use in Open-cut Mines
    1. 11.3.1 Conditions of ash placement
    2. 11.3.2 Ash use in US open-cut mines
    3. 11.3.3 Ash use in Australian open-cut mines
  4. 11.4 Ash Use in Underground Mines
    1. 11.4.1 Ash backfill for ground support in Australian underground mines
    2. 11.4.2 Ash in mine filling for motorway construction
    3. 11.4.3 Stabilisation of mine voids in urban areas
    4. 11.4.4 Ash for underground support in other countries
    5. 11.4.5 Geotechnical properties of ash for underground use
  5. 11.5 Mine Water Quality and Control
    1. 11.5.1 Formation and control of acid waters in coal and metal mines
    2. 11.5.2 Direct treatment of acid mine waters
    3. 11.5.3 Indirect use of ash in drainage control
  6. 11.6 Other Beneficial Uses at Mine Sites
    1. 11.6.1 Fire control in seams and refuse emplacements
    2. 11.6.2 Ash as a contaminant barrier
    3. 11.6.3 Ash use in mine soils and rehabilitation programs
  7. 11.7 Test Programs for Mine Backfill Applications
    1. 11.7.1 Evaluation of mine site conditions
    2. 11.7.2 Evaluation of ash and rock leaching characteristics
    3. 11.7.3 Interaction of ash leachate and mine rock materials
  8. 11.8 References

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