Open Cut

Vol 1: The Self Heating of Spoil Piles : A Field Trial of Fly-Ash Grouting and an Assessment of Cover Materials. Vol 2: Guide to the Recognition, Management and Prevention of Spoil Pile Self-Heating

Open Cut » Environment

Published: April 98Project Number: C3055

Get ReportAuthor: John Carras, A Maitra, OC Roberts, Abou Saghafi, F Szemes, David Haneman, Murray Phillips | CSIRO Energy Technology, ACIRL, IMEC Independent Mining & Equipment Consultants, Earth Technology

This report presents the results of an ACARP funded study carried out by Coal Processing Consultants (an ACIRL and CSIRO Division of Coal and Energy Technology joint venture) on aspects of spoil pile self heating. The specific objectives of the project were;

  1. To trial fly-ash grouting as a method of fire control on part of a fully instrumented burning spoil pile.
  2. To evaluate the performance of the fire control method.
  3. To investigate the clays and overburden materials at selected mines to measure their suitability as barrier materials for covering spoil-piles to minimise self-heating.
  4. To produce an updated Operator's Manual.

The project was conducted in close cooperation with the following five companies; Bayswater Colliery Company (Bayswater); Drayton Coal Pty Limited (Drayton); Muswellbrook Coal (Muswellbrook); Pacific Power (Ravensworth Rehabilitation Site) and Peabody Resources (Ravensworth South).

The major findings of the project are as follows;

A flyash grouting trial was held on a section of hot spoil at Drayton. Both dry flyash and a water flyash slurry were used as the grout. The trial took place in a section of spoil which had been instrumented with 4 temperature and oxygen probes and contained an active fire. A total of 108 tonnes of flyash was injected over a period of three days. While the grouting had an immediate effect on the temperatures in the spoil pile it is too soon to conclude whether the grouting was successful in extinguishing the spoil pile fire. Further measurements will continue over the next 18 months as part of the ACARP funded project C6003 which began in early 1998.

The cost of the grouting trial was $18,000 for ~1200m3 of spoil. This corresponds to ~$15/m3 of spoil. It is considered that this cost could be reduced significantly for grouting carried out in a more commercial, rather than research, environment. Nevertheless the relative cost of the grouting compared to other options , such as excavation, water quenching or covering, will play a major role in determining whether grouting will find widespread application in surface mining for controlling spoil pile fires.

The properties affecting the performance of cover layers in inhibiting oxygen penetration into spoil were investigated. The diffusion of oxygen through selected inert overburden, including clay from Drayton, material from a pre-strip operation at Ravensworth and spent marine conglomerate from Muswellbrook showed that the diffusion coefficient for oxygen depended on the air filled voidage of the spoil. Calculations of the penetration of oxygen by diffusion through cover layers was found to require very thick layers of low voidage material to significantly reduce the flux of oxygen. Such low voidages are not normally achieved by tipping and compaction. Water is required in the cover layers to reduce the diffusive flux of oxygen, significantly. Consequently the water holding properties of potential cover materials are important. In this regard cover materials with a high proportion of fines (ie clays and silts) are required.

The desired characteristics of cover layers will depend on the proposed application. For fresh cold spoil, attention must be given to the availability of the cover layer material, its water holding capacity, its resistance to erosion as well as its response to geotechnical instability eg cracks in the spoil. For hot spoil undergoing spontaneous combustion the water in the cover layer must also be able to withstand the elevated temperature environment in which it will be placed. These features must be taken into account in determining the thickness of the cover layer and need to be determined on a site to site basis.

The ability to predict self heating in spoil piles was furthered during the study. This took the form of:

  1. comparison of the predictions from the CSIRO numerical model of self heating with measurements from two trial spoil piles and
  2. the use of the output from the dragline simulation program, 3D-Dig, as a materials distribution file for the CSIRO model of self heating


Health and safety, productivity and environment initiatives.

Recently Completed Projects

C27039True Triaxial Strength Of Coal Measure Rocks And Its Impact On Roadway Stability And Coal Burst Assessment

Rocks in the ground are subject to a range of stresses. The stresses...

C3063Underground Vehicle Design Standards And Statutory Implications

The Australian underground diesel vehicle fleet has evolved since di...

C3064Conveyor Belting And Lagging Shear Characteristics - Drive Drum Slip

The primary aim of this project was to investigate the relationsh...


Open Cut

Safety, productivity and the right to operate are priorities for open cut mine research.

Recently Completed Projects

C29021Assessing The Impact Of Consecutive Night Shifts On Night-Time Alertness, Daytime Sleep And Timing Of The Circadian System

In the Australian coal mining industry, most guidelines for managing...

C33037Quantifying Recharge To Groundwater Systems In The NSW Coalfields (Sydney, Gunnedah And Gloucester Basins)

The purpose of this project was to estimate the rate of diffuse rec...

C26029Geological Controls On Fluorine And Phosphorus In Bowen Basin Coals

Increasing global restrictions on fluorine in product coal prompted ...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C27064Dry Beneficiation Using FGX And X-Ray Sorters

Conventional dry processing methods engage a single beneficiation de...

C26010Multi-Sloped Screening Efficiency With Changing Strokes, Frequencies, Feed Solids And Feed Rates-Pilot Plant Study

Optimising multi-sloped screens is often described as an art and the...

C28059Impact Of Water Quality In Coal Handling And Preparations Plants

The objective of this project was to deliver a concise reference do...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

C23052Novel Stone Dust Looping Process For Ventilation Air Methane Abatement

This multi‐phase project is concerned with the mitigation of m...

C27054Optimisation Of A Thermal Flow Reversal Reactor For Ventilation Air Methane Mitigation

Ventilation air methane (VAM) generally accounts for 50-85% of the t...

C28076Selective Absorption Of Methane By Ionic Liquids (SAMIL) - Phase 2 Demonstration In A Packed Bed Reactor

An alternative approach to high temperature oxidation of ventilation...

Mine Site Greenhouse Gas Mitigation

Low Emission Coal Use

Step-change technologies aimed at reducing greenhouse gas emissions.

Recently Completed Projects

C17060BGasification Of Australian Coals

Four Australian coals were trialled in the Siemens 5 MWth pilot scale ga...

C17060AOxyfuel Technology For Carbon Capture And Storage Critical Clean Coal Technology - Interim Support

The status of oxy-fuel technology for first-generation plant is indicate...

C18007Review Of Underground Coal Gasification

This report consists of a broad review of underground coal gasification,...

Low Emission Coal Use

Mining And The Community

The relationship between mines and the local community.

Recently Completed Projects

C16027Assessing Housing And Labour Market Impacts Of Mining Developments In Bowen Basin Communities

The focus of this ACARP-funded project has been to identify a number...

C22029Understanding And Managing Cumulative Impacts Of Coal Mining And Other Land Uses In Regions With Diversified Economies

The coal industry operates in the context of competing land-uses that sh...

C23016Approval And Planning Assessment Of Black Coal Mines In NSW And Qld: A Review Of Economic Assessment Techniques

This reports on issues surrounding economic assessment and analysis ...

Mining And The Community


National Energy Research,Development & Demonstration Council (NERDDC) reports - pre 1992.

Recently Completed Projects

1609-C1609Self Heating of Spoil Piles from Open Cut Coal Mines

Self Heating of Spoil Piles from Open Cut Coal Mines

1301-C1301Stress Control Methods for Optimised Development...

Stress Control Methods for Optimised Development and Extraction Operations

0033-C1356Commissioned Report: Australian Thermal Coals...

Commissioned Report: Australian Thermal Coals - An Industry Handbook