A condition where a coal seam or rock formation has been heavily fractured, crushed, or loosened by geological stress or nearby blasting. Shaken ground is extremely unstable and prone to sudden collapse, requiring immediate and heavy timbering or bolting. While it makes the actual cutting or digging easier, the severe risk of roof falls makes it a dreaded condition for underground crews.
Heard on the job
Watch your head in the next crosscut, the roof is badly shaken from yesterday's blast.