Proceedings of the 28th Annual Conference on Deep Foundations, 2003, Miami Beach, FL "Deep Foundations in Compressible Soil and Soft Rock", (DFI)
Cut-off Walls for Diamond Mining in the Artic
Wolfgang G. Brunner, Stefan K. Schwank
A 3800 m long temporary water-retaining dike has been constructed under extreme conditions in the harsh northern climate to enable two of the kimberlite pipes at the Diavik Diamond Project reserve to be mined using open pits. The Diavik Diamond Project is located on East Island at Lac de Gras in Canada’s Northwest Territories, approximately 200 kilometres south of the Artic Circle. The dike which has been constructed in up to 25 m deep water from crushed granite quarried from the site projects into Lac de Gras encircles the first two of the kimberlite pipes to be mined. An 800 mm wide diaphragm cutoff wall constructed of bentonite, cement and crushed rock, totalling 33,000 m², and a two phase jet grouted curtain wall at its base, totaling 8,400 m², have been installed through the dike and underlying till foundation into bedrock. The cut-off is designed to minimise water seepage from Lac de Gras through the dike. In order to ensure that the dike had adequate internal stability and diaphragm wall construction could proceed safely, the crushed rock fill material dumped into the lake was first compacted by TR 75 deep vibrators. In 2000, Bauer Maschinen GmbH of Schrobenhausen, Germany were awarded the contract for the supply of all specialist foundation equipment required on site and for providing technical support to the Canadian main contractor Lac-de-Gras-Construction throughout the construction of the cut-off walls during 2001 and 2002. Installation of the cut-off walls was completed in July 2002, three weeks ahead of schedule, and dewatering of the inner dike areas commenced just 5 days later and has continued throughout August and September. After completion of extensive testing of the diamond recovery plant, the mine is scheduled to go into full open pit production in February 2003.
|article #1203; publication #66 (AM-2003)|