Difference between revisions of "Vertical crater retreat"

Revision as of 18:22, 9 February 2011

From Queen's University Mine Design Wiki

This article is about the orebody requirements and developmental steps involved in Vertical Crater Retreat planning and mining.

Vertical crater retreat (VCR), also known as Vertical retreat mining, is an open stoping, bottom-up mining method that involves drilling large-diameter holes into the orebody vertically from the top, and then blasting horizontal slices of thethe orebody into an undercut. 

Similar to Sublevel open stoping and Blasthole stoping methods, VCR mining is used for steeply-dipping (>45º), or both vertically and horizontally large orebodies with competent ore and waste rock strength.  It differs from other open stoping methods in that it is a bottom-up method, as opposed to a left-to-right method, and it does not require the excavation of sublevel drifts before blasting and mucking can take place.

Holes are typically 165mm in diameter, allowing for a blast pattern spacing of 4.0 by 4.0m, and the thickness of one slice of ore varies between 2 and 5m ^[1].

History

Orebody Characteristics

VCR is a suitable mining method for orebodies that exhibit the following characteristics:

Advantages

• Safety: miners are working in a drift taht is adequately ventilated and has a fully supported roof.  Furthermore, no workers are required to work inside the stope, minimizing the risk of unexpected injuries.  As automated Machinery can be used, workers are not at risk of equipment-related injuries
• Good Recoveries: Continuous mucking from the drawpoints can take place after blasting.  In addition, VCR mining can be used with a high degree of mechanization, generating a high level of productivity.
• Cost: Once the pre-mining development is in place, VCR mining has a low operating cost, as it is a bulk mining technique and employees are not required to manually operate the mucking machinery
• Wall Support: VCR stoping shares some great features with sublevel open and shrinkage stoping.  Good wall support is offered during the VCR stoping phase, using shrinkage ^[3]  

Disadvantages

• Dilution of ore can result if waste rock is less than competent in strength, or improper blasting techniques are carried out.  Furthermore, sorting is not possible with VCR mining
• Risk of drawpoint blockage: if improper blasting techniques are carried out, large rocks can get lodged in the drawpoint and retard the movement of material through them, resulting in lost production
• a Large capital investment is required to establish the essential drift infrastructure required for proper VCR mining to take place, which can cost a lot of money up front.  Furthermore, the acquisition of equipment is necessary before mining can occur.
• Subsidence of overlying stope zones can be a problem as open stope expanses are left after mucking.  This can be avoided by using a backfill

Mine Development

References

1. ↑ "Vertical Crater Retreat -VCR." 2008. Atlas Copco. http://194.132.104.144/Websites%5CRDE%5Cwebsite.nsf/$All/2B0103C539FA78984125674D004AA392?OpenDocument
2. ↑ Archibald, J. F. "Mining Systems and Methods." 2007. MINE 210. Department of Mining Engineering, Queen's University at Kingston.
3. ↑ Osborne, Kelly and Baker, Vern. "Vertical Crater Retreat Mining". SME mining engineering handbook, voloume 2, 1992.