ABSTRACT: Special foamed cements were used to stabilize and secure caving ground in a newly-reamed 3.8 m (12.5-ft) diameter underground ventilation raise. Two zones of very poor Rock Mass Rating (RMR) material were encountered during reaming of a ventilation raise at Placer Dome?s Turquoise Ridge Mine in Northern Nevada. These zones caved to large cavities, continued failing, and could not be safely secured using standard rock bolting, wire mesh, and shotcrete procedures. In stable sections of the raise, the ground control plan called for the contractor to install 2.4 m (8-ft) and 3.7 m (12-ft) length resin grouted No. 7 Dywidag bolts, chain-link fence mesh and shotcrete. This work was conducted on three decks installed on the raise bore reamer. The first of the caved areas was approximately 1150 m3 (1,500 cubic yards) in volume and extended out to 12.2 m (40 ft) beyond the wall of the raise. Placer Dome considered several options for structural fill to repair the area including pumped shotcrete, concrete, and placing and grouting aggregate. A safe, cost effective, and expedient method of stabilizing the raise with foaming grout and bolted liner plate was selected and successfully executed. The special fast-setting, foaming cement grouts used were Tekfoam and Tekseal® manufactured by Minova. The raise was quickly placed in service. Factors considered in selecting the foaming grout are discussed.
An innovative technical approach is used to stabilize a newly reamed 3.7 m 12.5 ft diameter ventilation raise in Placer Dome?s Turquoise Ridge underground gold mine in Nevada. Rapid setting flowable cementitious fills, Tekseal and Tekfoam manufactured and supplied by Minova, were used to stabilize an actively forming cavity in the newly reamed ventilation raise. The use and application of these products enabled the ventilation raise to be successfully completed.
Placer Dome?s Turquoise Ridge Mine is an underground gold mine within Placer?s Getchell Mining property located in the Potosi Mining District of Northern Nevada. The Getchell property includes the Getchell mine, an underground portal mine and the Turquoise Ridge Mine, a vertical shaft underground mine, both of which are located on the Eastern flank of the Osgood Mountains. The Turquoise Ridge Mine is a joint venture between Placer Dome and Newmont Gold.
Gold was discovered on the Getchell Property in 1934. Under Getchell Gold Corporation ownership, in 1996 shaft sinking commenced on the Turquoise Ridge project with underground production commencing in May of 1998. Getchell Gold Corporation and Placer Dome merged in May of 1997. The property was placed on care and maintenance in December of 2001 and in December of 2002 the Getchell mine was restarted using contractors. In April of 2003 a restart plan was finalized for the Turquoise Ridge Mine.