Vintage: Coalbrook mining disaster in January 1960, Free Sate
The Coalbrook mining disaster is the worst mining disaster in the history of South Africa. The disaster occurred in the Coalbrook coal mine of Clydesdale Colliery on 21 January 1960 at around 19h00 when approximately 900 pillars caved in, almost 180 metres underground. The mine is situated in the Northern Free State, 21km south west of Vereeniging. About 1 000 miners were in the mine at the time and 435 died after being trapped, while the rest escaped through an incline shaft. The miners were suffocated by methane gas and crushed to death by rockfall. Miners felt a strong blast wind, many of whom rushed up to the surface but were instructed to return underground or face imprisonment. Only two miners refused to go back underground. 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. When microphones were lowered, no signs of life were detected. After 11 days the rescue was called off. With too much methane and carbon monoxide in the mine for any rescue team to penetrate the South East of section 10, one of the solutions was to drill from the surface all the way down into the entombed shaft. A sophisticated new drill rig at the time was used but the drill bits wore down as they encountered hard lava rock.
On the 28 December 1959 a collapse occurred in the northern part of the mine (section 10), which included the area where the top coaling experiment was done. That collapse was arrested by a barrier wall to the south. Coal extraction from the south end of the section was not affected. An inspector of mines came on a routine inspection two weeks later. He was not informed about the collapse.
At approximately 16h00 on 21 January 1960, miners in a section just west of the collapsed area heard shot-like noises and felt a strong blast wind. The area was evacuated and the mine manager informed. Miners from the area just south also heard the noises and withdrew.
The acting mine manager and overseer entered the mine to inspect. Some of the ventilation piping had been damaged. At the same time it was reported that there was a subsidence on the surface of section 10. It was concluded that the 'weight had come off' and it was time to send in a repair team. Production in the south-eastern section was not affected and mining there carried on uninterrupted.
The repair team working on the ventilation piping became aware of thundering noises at just after 19h00 and withdrew to a safe area. On the way they were overtaken by a hurricane of dust and more noises. A general exodus from the mine ensued. It was later noticed that not a single miner from the south east side of section 10 had come out and it had to be assumed that they were trapped.
The rescue effort
Rescue was attempted from above and below. Proto teams entered the mine in an attempt to find a way through to the trapped miners. This proved to be very dangerous due to high concentrations of methane and carbon monoxide and from the still unstable rock. The proto teams experienced instability, falling rocks and water.
The alternative to digging through from the bottom was to drill down from the surface. Anglo American offered their new drill rig that had recently been installed at Ellisras. It was transported by road and arrived three days after the event. It was equipped with a 13½ inch (340mm) drill point. It started operating on the 24 of January and made good progress until it met the dolerite strata. Dolerite is a very hard lava rock. Progress slowed down, it was reported that on one day the drill only managed 15 feet (5m). The rock also caused severe wear on the drill bits requiring it to be changed frequently. A new supply of drill bits had to be flown in from Texas.
Two more drill rigs arrived at the site on the 29th, drilling in close vicinity to the Anglo drill rig, which is where the trapped miners were believed to be situated.
The Anglo drill penetrated to a depth of 515 feet (160m). When it got into an open space, a microphone was sent down but picked up only the sound of dripping water.
Parallel to the drilling there was also a team of shaft sinkers to dig a rescue shaft. They had dug down to a depth of 150 feet by the time the rescue effort was called off. The top end of the shaft was later sealed off with an apron of concrete.
Mining was resumed on the 18 March in the non affected areas. By March 1961 the mine was supplying ¾ of the requirements for the two power stations. And then in March 1961 another shift in the strata occurred. As a consequence of that, mining from the North shaft was abandoned. Coalbrook South, which had been sunk to supply the new Highveld power station, continued producing until 1990. Another area was developed from the East shaft, which was situated next to the Heilbron Road.
For many years after the event nothing was put up as a memorial. In 1996, after the closure of Coalbrook South, the village and the workshops were bought by Richard Hse. He agreed to have a memorial erected. Using one of the coal cutters from the mine serving as a backdrop to an inscription on a stone plaque which reads:
IN MEMORY OF THOSE 435
MINERS WHO LOST THEIR LIVES
IN THE COALBROOK-MINE DISASTER
“AFTER ALL THOSE YEARS YOU ARE
STILL IN OUR HEARTS AND THOUGHTS"
Causes of the disaster
The production at the mine had increased from 134 230 tons per year in 1954 to 2 260 660 tons per year by 1958, in response to the newly built Taaibos power station at Kragbron.
The accident was caused by cascading pillar failure 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 included 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.Top coaling began as a method of increasing production in areas that had already been mined. In 1932 the tunnels were 2,4m high, in 1948 some top coaling was done to raise the height to 3,7m 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 6,1m. On 28 December 1959 a collapse occurred in the northern part of the section 10 mine, an area where most of the top coaling experiments were done. That collapse was stopped from spreading by a barrier wall to the south end of section 10. This incident did not affect coal extraction from the south. However, it did go unreported to mining inspectors.
In the months following the disaster, four different inquiries were launched under the Mines and Works Act of 1956, with the third one being a judicial inquest. The inquests found that the deaths occurred as a result of the subsidence of the mine itself. They also revealed that the collapse of 28 December was not reported to mining inspectors, as was mandatory.
Following the disaster, the South African government established Coal Mines Research Controlling Council to improve coal mine safety and research pillar strength, supported by the Council for Scientific and Industrial Research and the Chamber of Mines Research Organisation.
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.
Source: The Heritage Portal
Article author: Horst Müller