prevention and control of spontaneous combustion - Mining and

the Kleinkopje area since the early 1900s. The mine produces 8 Mtpa RoM, leading to export
sales of 4.5 Mtpa. The mine typically makes use of four or five draglines.
Kleinkopje Colliery has a unique geology. There is a massive syncline structure and the seam
gets deeper towards the east. There are currently four pits operating at the mine, namely 5 west
south, 3A north, 2A north and 2A South, with most mining taking place in the No. 2 seam, which
was mined previously. The coal reserves are predominantly found in the No. 1, No. 2 and No. 4
seams.
The mine is currently experiencing serious spontaneous combustion problems in the highwalls
and, in addition, spoils begin to burn after about two months. The problems in each of the four
pits are discussed separately.
5 west south – This pit is predominantly mining virgin No. 2 seam, with a portion of production
coming from the No. 1 seam. The coal is poor quality and typically has a calorific value of 18
MJ/kg to 19 MJ/kg. Once the highwall is exposed it starts burning. Burning also takes place on
the edges of the spoil material.
3A north – In this pit mining can potentially take place in the No. 1, No. 2 and No. 4 seams.
Currently this pit is mining virgin No. 4 seam coal. However, the No. 2 seam has been pre-mined
and mining in the No. 1 seam has not yet started. There is a massive syncline in the highwall of
this pit and the overburden thickness is between 15m and 30m with an interburden of between
18m and 25m. Since overburden thickness is not constant, accurate drilling becomes
problematic and sometimes blast holes penetrate into old workings. These open blast holes
usually create a chimney effect and this is a contributory factor in the spontaneous combustion
problem. The depth of the No. 2 seam is between 60m and 70m because of a scissor fault.
There is very little sand or soft material available in this pit to combat spontaneous combustion,
which results in insufficient and intermittent cladding of the highwall to control the outbreaks of
spontaneous combustion.
2A north – Mining takes place in both the No. 2 and No. 4 seams. The overburden thickness is
on average 25m, with the top 15m being soft overburden. Spontaneous combustion is not
prevalent in this pit, however, some heating has been experienced in the eastern part of the pit
during coaling operations.
2A south – Three seams: No. 1, No. 2 and No. 4 are being mined and this area was extensively
mined by underground operations, with these previous workings being flooded. Because the pit
has experienced extensive spontaneous combustion problems, interventions have been
developed and tried over several years. These include buffer blasting, double cuts, dewatering
at 5 ML/day and constant monitoring. One of the major challenges in this pit is an intersection
point between two ramps R10-9 and R7-6 that, at the time of the visit, turned the highwall
through an angle of 113 o thus increasing spontaneous combustion because air entered the old
workings from two directions
2A south is the only area in the mine where there is sufficient sand and soft material in the
overburden to ensure proper cladding. Roughly 15m to 30m of the overburden is suitable for this
purpose. However, in the rainy season mining condition deteriorates and, in the interests of
safety, no cladding is undertaken.
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