1900 points of all stopes, i.e., the position where the initial raise is drilled, stays exact at the same position, irrespective of the shape of the later developed stope. The basic stope layout follows a grid with 45 m gridpoint spacing. All secondary and tertiary developments in a block are identical for the three stope layouts. Typically, a block will be prepared for future stoping by developing raises, extraction and haulage drifts. Following the concept of the flexible stope layout, it is possible to decide after the block’s development and based on the in situ observation of the rock mass conditions and ore quality during raise boring and drifting which stope layout should be implemented best. Table 2 shows the key figures for the three different stope layouts. Stope sizes, recovery rates, number of stopes to be mined during full production of 5 Mio t in 10 and 30 years, respectively, are compared in Table 2. Table 2 – Key figures for different stope layouts Option 1 Option 2 Option 3 Stope cross section [m²] 1 582 1 754 1 186 Stope height [m] 300 300 300 Stope volume [m³] 397 533 431 291 299 896 Recovery rate (2D) 47% 52% 36% Nominal production [Mt/y] 5.0 5.0 5.0 Stopes to be mined in 10 years 27 25 36 Stopes to be mined in 30 years 99 91 131 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 mineplanning 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 0 200 400 600 800 1000 1200 v1 v2 v3 v4 v5 v6 dri$ length [m] design version secondary development Transport drifts: 379m Draw drifts: 330m Loader-truck crosscuts: --- Total drifts: 709m V4
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