coal pillar

Does it mean that there would ordinarily be coal pillars either side.

Narrow driveage doesn't necessarily mean then that there are coal pillars either side.

Chris thinks roof bolts should only be allowed where the section's are supported by thick coal pillars.

Normally the roof bolted sections would rest on coal pillars sometimes fifty metres wide.

Ford huddled in the lee of the coal pillar, head down, as coal and rocks blew past.

There has to be good coal pillar support on either side and there has to be a competent roof.

A massiveboom followed, a wave of overpressure ripping through the mine, picking him up like a leaf and hurtling him into a coal pillar.

The men had been pillaring, or second mining, which involves extracting the last remaining coal in tunnels by scraping it from the coal pillars used to hold up the roof.

Those were not the circumstances at Bilsthorpe, but the mines inspectorate insist they were right to allow the roof bolting in the tunnel, or narrow driveage that's despite the fact that on one side instead of a good coal pillar, only wooden props supported the roof.

"Well... I can think of two times: when you need to get coal out in a hurry and you're not going to keep mining; and when you've mined everything else and you're willing to build up new pillars to bear the load while you work the coal pillars," Kindan said.