DYWIDAG SYSTEMS International USA has used geogrid to reduce the risk of damage from rock falls in Boonsboro Quarry in Lexington, Kentucky.
The Allen Company's underground limestone mine produces more than 2.5Mt of crushed stone a year for building and repairing roads. Mining has left cathedrallike underground rooms up to 25m high, with 15m wide pillars supporting the roofs.
In some areas further excavation has extended the pillars to more than 60m high and there has been some spalling, with chunks of rock falling on and severely damaging mining equipment.
DSI USA's solution was to wrap lightweight geogrid around the pillars and bolt it into place, minimising the risk of rock falls.
Bolting was carried out from an outrigger fitted to one of the mine's telescopic cranes.