Longhole mining under caved ground at Eagle Point Mine

CIM Edmonton 2004
Rimas Pakalnis,
Abstract This paper summarizes the successful extraction of ore underneath stabilized previously unconsolidated backfill/caved material by longhole method in weak ground.

In order to mine 150-375 stope the loose caved material in and above the FW drill drift had to be stabilized. This was attempted by drilling a pattern of groutable extension rods and pumping a cement grout to create a reinforced cemented rockfill plug supporting the overlaying loose rockfill and forming a section of the stope back. The plug design was assessed analytically based on sound engineering principles. Integrity of this plug was controlled not only by its own strength but also by the stability of the ore pillar on one of its sides, which proved to be the weakest link of the whole system.

Longhole mining of 150-375 stope started in early December 2003 and took about 3 weeks. As blasting progressed the ore pillar, which became a centre of the open stope’s back gradually disintegrated. With the final blast the whole stope back collapsed and the loose fill from the adjacent caved areas ran into the stope.

The attempt to stabilize the 150-375 stope back did not result in a long term stability, but allowed for almost 100% recovery of ore.
Keywords: loghole mining, Rock mechanics, Grouting, rockfill stabilization
Full Access to Technical Paper
PDF version for $20.00
Other papers from CIM Edmonton 2004