Rock bolts cleared of causing pit disaster: Inquiry backs roof support system used when three died

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A CONTROVERSIAL rock-bolting system did not cause a tunnel roof collapse that killed three miners, a report said yesterday.

But the inquiry into the disaster at Bilsthorpe Colliery, Nottinghamshire, last August recommended that the practice of 'skin-to-skin' working - where two tunnels are driven alongside each another - should end.

David Eves, deputy director general of the Health and Safety Executive, said yesterday: 'The accident has taught us that we just don't know enough about the potential for movement in the upper strata when roadways are being driven in the 'skin-to-skin' mode.

'That was not apparent to anyone concerned before the accident.'

The final report by HSE investigators suggests that rock bolts, driven into strata to support the roof instead of conventional supports, may even have helped some of the men escape.

It found that the fall was caused by movement of rock in nearby abandoned workings, probably triggered by high rate of advance in the tunnel.

The Health and Safety Commission has appointed Sir Bernard Crossland of Queen's University, Belfast, to carry out independent public investigation into any new or further evidence that may exist.

The men who died were David Shelton, 31, a colliery under-manager, Bill McCulloch, 26, and Peter Alcock, 50.

Bilsthorpe was one of 12 mines on a market-testing list when the cave-in occurred. There were allegations after the tragedy that managers were pushing ahead too quickly on work to open up new coal faces and keep the pit viable.

The report said the roof fall was in a roadway being driven through coal in the 'skin-to-skin' method.

It found that the fall was caused by a movement of rock in strata high above the roadway due to a reconsolidation or movement of the waste (or fallen rocks) in the abandoned area, which would normally have held the higher strata in place.

The report recommended that 'skin-to-skin' working next to worked out areas should end.

It also recommended further research on factors affecting the siting of new roadways and an extension of reporting procedures in connection with falls of ground. British Coal welcomed the findings and said: 'We are completely in accord with the inquiry's conclusions and we are already implementing the recommendations made by the investigators.

'For many years, British Coal has driven similar roadways at collieries, particularly in the Midlands, without major incident. All such developments have now been stopped.'

The company believed the strata failure at Bilsthorpe was caused by a 'rare combination of factors'.

The report suggested the tragedy was not reasonably foreseeable.

The pit's strata monitoring system had been installed to recommended standards and performed as designed. But neither it nor any other system known to be in common use was capable of detecting or giving warning of such rapid strata movement as occurred at the time of the fall, the report said.

It added: 'It is considered that the rate and magnitude of the fall was such that any free-standing support conventionally used would have been unable to withstand the load.'