OFFICIAL Figure 7 – Comparison of different drift lengths for tertiary development on the haulage level of a mining block needed for options V1 to V6; right side: optimized secondary and tertiary development at the haulage level of a mining block (version V4). The planned Fen approach uses sequential raise stopes mined adjacent to previously backfilled stopes, leveraging backfill to improve stability and extraction. However, this introduces stringent mine-planning and operational constraints driven by backfill curing. Unlike concrete (nominal strength in ~28 days), cemented paste backfill may require ~12–24 months to achieve adequate strength. With a 24-month curing assumption, a 12-stope panel could take about six years to complete, implying that multiple extraction areas operating in parallel are needed to meet high annual production targets – while also enabling more stable, predictable scheduling. Six different options for tertiary development in a block have been considered and designed. They differ – among other details – in the number and orientation of transport drifts. As documented in Figure 7 the drift length for tertiary development on the haulage level of a mining block differs between some 1 050 m and 700 m. A comparison of the different drift lengths needed for options V1 to V6 is shown in Figure 7. A 3D visualization of the mine’s developments and stopes after a Life of Mine of approx. 20 years is given in Figure 8. Figure 8 – Visualization of the mine layout including drifts and stopes; left side: visualization of the mine’s infrastructure consisting of the main ramp and decline (red color), primary developments on the three main levels (orange color) connected by four ventilation shafts (blue color), one gravity shaft (grey color) and secondary and tertiary development (blue color) at the access and haulage levels; right side: mined and backfilled stopes are shown. 0 200 400 600 800 1000 1200 v1 v2 v3 v4 v5 v6 drift length [m] design version Transport drifts: 379m Draw drifts: 330m Loader-truck crosscuts: --- Total drifts: 709m V4
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