Geological factors influencing the design of a narrow-reef autonomous gold miner

Transcription

1 Geological factors influencing the design of a narrow-reef autonomous gold miner Dr George Henry and Dr. Jan Kuijpers Centre for Mining Innovation (CMI) 31 August 2011

2 Introduction CMI focus areas Real time risk management monitor underground conditions Human factors in mining safety, health (dust, diesel fumes, heat, hearing loss, stress) Novel mining methods autonomous mining, non-explosive rock breaking, in situ leaching CMI Carlow Road Campus CSIR 2011 Slide 2

3 Why autonomous mining? Costs Safety Resources to reserves CSIR 2011 Slide 3

4 Costs Deep underground mining expensive capex, labour, electricity Comparison current gold price ~ US$ 1 700/ounce (R /kg) Mine headgear Closed West Wits Consolidated open pit mine surface mine cut-off grades ~ 1g/t Au typical deep South African gold mine cut-off grades ~ 7 g/t Au over a 1m stoping width CSIR 2011 Slide 4

5 Safety Tau Tona Gold Mine Underground mining is a high risk activity high stress environment mining-induced seismicity rock falls rock bursts rock handling accidents box-holes, tramming heat and humidity Reduce number of miners exposed to high risk areas (working face) CSIR 2011 Slide 5

6 Increase reserves South Africa has over 40% of the world s gold resource base, according to the Department of Mineral Resources metric tons Most are in the SAMREC resources category deep CMI research convert much of the resources into mineable reserves in the future using novel, safe mining technologies Basal Reef Free State Visible gold with carbon Red scale bar 1 mm CSIR 2011 Slide 6

7 Savuka Gold Mine Underground core drilling How? Great Noligwa Mine Photo: courtesy AngloGoldAshanti Conventional mining methods 1 m stope width drill and blast labour intensive Longhole mining drill and blast <1 m stope width, ~70-80cm can be partly mechanised Narrow reef autonomous mining designed to be <50cm high autonomous minimal human control mines only ore no waste Burnstone Gold Mine longhole mining Photo: courtesy Great Basin Gold CSIR 2011 Slide 7

8 Narrow reef autonomous mining machine - concept Functional attachments - Underground navigator - Sounding device - Gold analyser - 3D scanner mapping - rock breaker - miner Courtesy Dr. D. Vogt Platform Max. height < 50cm CSIR 2011 Slide 8

9 Geological factors - critical Dip of reef typical Wits at surface 45 to 70 Langlaagte outcrops of Main Reef ideal dip 0 to 30 otherwise too steep Standard Bank Museum Main Reef Stope CSIR 2011 Slide 9

10 Geological factors critical Strength of rock Quartz-rich Tough! Rock Breaking Drill and blast - cheapest Non-explosive impact ripper drilling out the reef controlled foam injection diamond wire cutting electrical methods Main Reef Leader City Deep Gold Mine CSIR 2011 Slide 10

11 Geological factors - critical Gold Analyser COMRO 1990 Nature of the orebody Composition/mineralogy gold in situ detection XRF Laser uranium radioactivity pyrite XRF carbonaceous matter CSIR 2011 Slide 11

12 Geological factors - critical Savuka Gold Mine Joints Structural disturbance Folding determines amount of dip Faulting abrupt disruptions Ideally map out area ahead of mining, but not always possible CSIR 2011 Slide 12

13 Free State Goldfield - folding 113 Level - ~30=00 below surface From: McCarthy, 2006 CSIR 2011 Slide 13

14 Free State Goldfield - faulting Faulting of Basal Reef 113 Level - ~30=00 m below surface CSIR 2011 Slide 14

15 Geological factors - other Kimberley Reef - Gold Reef City Hanging-wall rocks Determines roof support - costly horizontal parting planes bedding planes cross beds CSIR 2011 Slide15

16 Geological factors - other Kimberley Reef Gold Reef City Footwall rocks quartzitic stable shaley heaving of footwall CSIR 2011 Slide 16

17 Kimberley Reef - Gold Reef City Footwall heaving CSIR 2011 Slide 17

18 Geological factors - other Savuka Gold Mine Core discing high stress Underground stress orientation determination of mining direction South Africa principal stress σ1 vertical (at depth) general σ2 NW-SE direction local modification by faults, dykes/sills CSIR 2011 Slide 18

19 Geological factors - other Dykes and sills Ages Ventersdorp (~2700 Ma) Pilanesberg (~ 1120 Ma) Karoo (~180 Ma) In general not problematic unless associated with fault displacements CSIR 2011 Slide 19

20 Geological factors - other Carbon Leader structure contours Depth Autonomous miner will be designed for extreme depths 4000m 4500m 5000m CSIR 2011 Slide 20

21 Geological factors - other Type of conglomerate reef matrix- or clast-supported thick or thin VCR carbon-seam CSIR 2011 Slide 21

22 Geological factors - other Blyvooruitzicht Gold Mine Carbon Leader Reef Gold distribution bottom loaded in carbon seam top loaded py disseminated Au CSIR 2011 Slide 22

23 Conclusion Geological factors play an important role in the design of any autonomous narrow-reef miner in South Africa. Thank you. Mapungubwe rhino (12cm) Questions? CSIR 2011 Slide 23