Long-hole plug: addressing the hazard of bogged rods in upholes.

Development, laboratory and underground field testing, and installation at the Rosebery mine, western Tasmania, Australia of long-hole plugs to alleviate the hazard of bogged and broken-off drill rods falling from an uphole are described. The long-hole plug consists of tapered cone section machined out of solid bar fitted in a slotted tube and has a sacrificial wooden dowel as locator. The plug is held in place by the slotted-tube component and, when struck by falling drill rods, the cone section is driven into the slotted tube which transfers the axial forces from the falling drill string horizontally into the rock mass. Results are presented of long-hole plug testing including static pull testing of the slotted-tube component, full-scale drop testing and Rosebery mine underground field trials (safety of installation and in-situ drop tests) as well as drop tests to compare the effectiveness of an alternative (plate-over) method. For the in-situ drop tests carried out in holes of 39 m in length drilled in the Rosebery rock mass, the long-hole plugs were found to stop the falling drill rods over a maximum distance of 150 mm.
Development, laboratory and underground field testing, and installation at the Rosebery mine, western Tasmania, Australia of long-hole plugs to alleviate the hazard of bogged and broken-off drill rods falling from an uphole are described. The long-hole plug consists of tapered cone section machined out of solid bar fitted in a slotted tube and has a sacrificial wooden dowel as locator. The plug is held in place by the slotted-tube component and, when struck by falling drill rods, the cone section is driven into the slotted tube which transfers the axial forces from the falling drill string horizontally into the rock mass. Results are presented of long-hole plug testing including static pull testing of the slotted-tube component, full-scale drop testing and Rosebery mine underground field trials (safety of installation and in-situ drop tests) as well as drop tests to compare the effectiveness of an alternative (plate-over) method. For the in-situ drop tests carried out in holes of 39 m in length drilled in the Rosebery rock mass, the long-hole plugs were found to stop the falling drill rods over a maximum distance of 150 mm.