WKP PFS – Geotechnical Section Approved by: Approval Date: TBA OceanaGold PEX-000-PLN-046-A Page 15 of 22 For the hanging wall and footwall, the slope distance for a 20m high stope that is dipping at 60o is 23m, therefore the actual HR in the hanging wall and footwall is 4.5. Since the actual HR for the stope design does not exceed maximum HR values for the 1st quartile rock mass (as per the table above), then no additional ground support will be required in the stopes. Of course, in the case of stoping on sub-parallel ore bodies with relatively small pillar distances, different rules will apply for the stope geometry and stope support. These rules were determined by numerical modelling, and they will be discussed in the numerical stress modelling section. Figure 12: Stope hanging wall design chart Figure 12, the design chart for stope hanging wall, shows that both the 1st quartile and 2nd quartile N’ plot in the “stable zone” for hydraulic radii of 4.5. The 2nd quartile N’ remains in the “stable zone” for hydraulic radii up to 7. This indicates that in the most typical ground conditions, the Avoca backfill cycle could be delayed, and the strike length of the open stope could be doubled from 15m to 30m.
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