Coalbrook mining disaster
The worst mining disaster in South Africa[1] occurred in the Coalbrook coal mine of Clydesdale Colliery on 21 January 1960[2] at around 19:00 when cave in occurred about 180 metres underground. About 1 000 miners were in the mine at the time and 435 were trapped.
Immediately after the incident, rescue teams arrived from other mines in the region and boreholes were drilled into areas where survivors were expected to be. But when microphones were lowered no signs of life were detected, there were no survivors. After 11 days the rescue was called off.[3]
Causes of the disaster
The production at the mine had increased from 134 230 tons per year (1954) to 2 260 660 tons per year (1958) in response to the newly built Taaibos power station[4] at Kragbron.
The accident was caused by cascading pillar failure (CPF)[5] where a few pillars fail initially and this increases the load on the adjacent pillars causing them to fail. This cascading failure caused pillar collapse over an area covering 324 hectares.
Factors contributing to the collapse were the process of top coaling which raised the height of the tunnels and pillar and panel mining reducing the size of structures holding up the tunnel roof.[6]
Top coaling
Top coaling began as a method of increasing production in areas that had already been mined. In 1932 the tunnels were 2.4 m high, in 1948 some top coaling was done to raise the height to 3.7 m, but the coal yielded was a poor grade and the practice stopped. In 1951 top coaling began once again as a new electricity power station had been built and it was able to use lower grade coal. The roof height was raised to 4.3 m and 5.5 m in places, and by 1957 top coaling was a significant contributor to production.
Some time between 1957 and 1959 experimental secondary mining was done in No.10 section to recover coal from a mined out area of the mine. Top coaling raised the roof height to between 4.3 and 6.1 m
Pillar and panel mining
The tunnels in the mine were between 6.1 and 6.7 metres wide. Pillars and panels of coal were left between the tunnels to keep the mine roof from collapsing.
- In 1905 the centres of the barriers and the pillars were 24.4 m apart
- From 1932 the pillars were mined to 19.8 m and barriers to 18.3 m.
- From 1943 the pillars were reduced to 18.3 m and the barriers 12.2 m (still separated by tunnels 6.1 to 6.7 m in width)
In this time "dummies" of 4 metres wide and 2 metres deep were mined out of the barriers, and in some cases up to four sides of the pillars too, to yield additional coal.
Response to the Incident
Following the disaster, the South African government established Coal Mines Research Controlling Council(CMRCC) to improve coal mine safety and research pillar strength, supported by the Council for Scientific and Industrial Research (CSIR) and the Chamber of Mines Research Organization (COMRO).
The South African Chamber of Mines obtained rescue equipment to reach men trapped underground in coal mines. Similar equipment was used to rescue trapped Chilean miners in 2010.
References
- ↑ "The world's worst coal mining disasters". Retrieved 1 April 2015.
- ↑ "More than 400 miners are killed in an underground collapse at Coalbrook mine". Retrieved 30 March 2015.
- ↑ Pogrund, Benjamin (14 October 2010). "The 435 SA miners who didn't make it". Retrieved 1 April 2015.
- ↑ "Coalbrook". Retrieved 2 April 2015.
- ↑ Malan, D.F. and Napier, J.A.L. (December 2011). "The design of stable pillars in the Bushveld Complex mines: a problem solved?". Journal of the Southern African Institute of Mining and Metallurgy. Retrieved 2 April 2015.
- ↑ van der Merwe, J.N. (December 2006). "Beyond Coalbrook: what did we really learn?" (PDF). The Journal of The Southern African Institute of Mining and Metallurgy 106: 857–868.
Coordinates: 26°51′11″S 27°52′44″E / 26.8531°S 27.8790°E