# A Review of the Impact of Spontaneous Combustion on Slope Stability in Coal Mine Waste Dumps
## 4 Monitoring and Mitigation Strategies Combating Spontaneous Combustion
### Mitigation Strategies  
Any combustion can be controlled by removing any one of the three essential components: fuel, heat and oxygen. In order to extinguish a fire, it is necessary to remove at least one of these components. Based on experience with spontaneous combustion in South Africa, the control measures can be divided into three groups: (1) control measures to reduce or eliminate oxygen from the fire process, including sealing agents, dozing over, buffer blasting, and the cladding of the highwall; (2) control measures to reduce the temperature (heat) and/or the reaction rate, including the injection of water, nitrogen, and carbon dioxide; and (3) the removal of heated or burning material for cooling the combustion sites and interrupting the reaction [163; 164; 165; 166]. Throughout the history of coal mining in Poland, a variety of methods have been employed to extinguish burning mine waste dumps or prevent their spontaneous combustion [1; 20; 81; 167; 168]. These measures include intensive sprinkling with water, covering dumps with nonflammable materials such as clays or tills, the isolation of parts of the dump that are on fire by digging absorption trenches filled with a water-ash mixture, the cooling of burning waste via its exploitation and the reconstruction of dumps, deep drilling into the dump to enable the filling of openings with water-ash pulp, cooling and quenching with neutral gases using pipes placed in the dump during its deposition, waste thickening with an incombustible material combined with dump dehydration in order to protect the dump from self-ignition and protect groundwater from chemical compounds leached from the deposited waste, covering the dump with polymeric compounds or antipyrogenic materials (sodium chloride, calcium chloride or manganese chloride), and utilizing ash from power plants during dump formation. At Australian mine sites, a number of control techniques have been incorporated into waste rock dump (WRD) design and mine planning to minimize the effects of spontaneous combustion and ultimately prevent it from occurring. These control measures are quite similar to those employed in South Africa and can be broadly categorized into three groups: measures to reduce/eliminate oxygen, such as sealing agents, the compaction of the surface material (dozing over, truck haulage routes or compaction), buffer blasting, covering the area of concern with inert material (e.g., non-acid forming material, clay), the application of a final cover layer with good water retention properties (e.g., fly ash-water slurry) and subaqueous deposition; measures used to reduce the temperature and lower the reaction rate, including water cannons, firefighting foam, the injection of water, water spraying, nitrogen injection and carbon dioxide injection; measures to eliminate the fire process, which may include the excavation of hot or burning material, controlling the morphology of potentially acid-forming material cells (layering, etc. ), the use of low-angle slopes to minimize the effects of wind (i.e., reduce \"chimney effect\"), the use of artificial wind barriers, submersion in water (e.g., backfill in pit and flooding), and the spreading of the affected material into thin piles to allow it to cool [13; 64; 169; 170]. Techniques or approaches that have been proposed and applied in the US, India and other countries include bulkheads and stoppings; inertialization; nitrogen or carbon dioxide gas injection; dynamic pressure balancing, ventilation control; the application of fire-fighting chemicals; the application of a surface coating or sealant material to prevent oxidation; high-expansion foam; excavation; isolation; inundation with water; surface seals; remote sealing; noncombustible barriers; hydraulic backfilling or 'flushing'; pneumatic stowing; and grouting [17; 171; 172; 173; 174; 175; 176; 177; 178; 179]. Alternative approaches are focused on the development of advanced materials that can be effectively used to combat combustion.