The CCUT block cave design for Cullinan Diamond Mine

Abstract

registered in 1902 and open pit mining activities commenced in 1903 (see timeline in Figure 1). The Cullinan Diamond, the largest rough diamond of gem quality in the world at 3106 ct, was found 9 m below surface (mbs) in 1905. De Beers acquired a controlling interest in Premier Mine in 1917 and open pit activities progressed down to 189 mbs. The mine closed during the Great Depression of 1932 and re-opened only after the Second World War. Dewatering of the pit began in 1945 and underground mining started in 1947 using variations of sublevel open-bench mining. Conventional-type cave mining started in the early 1970s, and sublevel open stoping was attempted in the early 1980s but was changed to mechanized panel retreat block caving. The BA5 and BB1E blocks (Figure 2) below the sill on elevations 630 mbs and 732 mbs respectively were changed from postundercut panel retreat caves to advance undercut block caves to reduce the tunnel deformation and failures caused by high abutment stresses on the production level infrastructure, which was developed and constructed ahead of the undercut face. The BA5 block cave can be considered a success, with high extractions achieved, especially in the hard western Hypabyssal Kimberlite, albeit with significant tunnel failures in the softer Grey Kimberlite zones close to the contact. The BB1E and AUC mining blocks that lie within the soft eastern Brown and Grey kimberlites respectively experienced massive tunnel failures early in their lives and a recovery level on 747 mbs had to be established to recover the remaining BB1E resource tons (see Figure 2 ). The mine was renamed Cullinan Diamond Mine (CDM) after the Cullinan Diamond as part of its centenary celebrations in 2003. Petra Diamonds acquired CDM from De Beers in November 2007. Petra initiated mining studies in 2008 to mine the CCUT resource defined down to 1073 mbs. Two declines to access the lower CCUT mining block were started in 2009 and 2010. Historical production from CDM ranged from 2 to 5 Mt/a). More than 360 Mt of kimberlite ore have been mined to date over 113 years, yielding approximately 128 million carats at 35 carats per hundred tons (cpht). CDM has produced over 750 stones that are The CCUT block cave design for Cullinan Diamond Mine