1032 1. Site screening and feasibility assessment 2. Engineering characterization and numerical analysis 3. Risk-informed performance evaluation 4. Multi-criteria decision-making and optimization This approach is aligned with international best practice and consistent with the Global Industry Standard on Tailings Management (GISTM) principles (ICMM, UNEP & PRI, 2020). 5.2 Site Screening and Feasibility Criteria Initial screening determines whether an exhausted open pit is suitable for use as an In-Pit TSF. Key exclusion and suitability criteria include: • Adequate pit geometry and residual storage capacity • Competent rock mass conditions and acceptable slope stability • Favorable hydrogeological gradients allowing inward seepage • Compatibility with mine sequencing and production schedules Table 3 summarizes the primary screening criteria applied during the prefeasibility stage. Table 3. Key site screening criteria for In-Pit TSF feasibility Criterion Evaluation focus Pit geometry Depth, volume, slope angles Rock mass quality RMR / GSI, structural fabric Hydrogeology Groundwater gradients, permeability Seismicity Regional seismic hazard Mine planning Alignment with life-of-mine 5.3 Integrated Geotechnical and Hydrogeological Analysis Detailed engineering assessment includes coupled geotechnical and hydrogeological analyses to evaluate long-term stability and containment performance. Geotechnical analyses focus on: • Pit wall stability under progressive tailings loading • Stress redistribution within the rock mass • Potential for time-dependent deformation Hydrogeological analyses assess: • Groundwater–tailings interaction • Seepage direction and hydraulic gradients • Long-term pore pressure evolution Numerical models are developed to simulate progressive pit filling, accounting for staged deposition and water management strategies. These analyses support verification of inward seepage conditions and stable groundwater regimes (Younger et al., 2002; Vick, 1990). 5.4 Risk-Informed Engineering Decision-Making Engineering decisions for In-Pit TSFs are guided by a consequence–probability framework consistent with international tailings risk management practices (Morgenstern et al., 2016). Overall risk Vis defined as: V=L 3 ×s3 (7)
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