108 Where: • = weighting factor for criterion • = normalized score for criterion Typical criteria include geotechnical suitability, hydrogeological performance, risk reduction potential, regulatory acceptance, capital efficiency, and closure performance. 6. PERFORMANCE EVALUATION AND RESULTS 6.1 Comparative Performance: In-Pit TSFs vs Surface TSFs A comparative assessment between conventional surface TSFs and In-Pit TSFs highlights fundamental differences in risk drivers, operational complexity, and long-term performance. Table 4 summarizes key comparative indicators. Table 4. Comparative performance indicators for surface TSFs and In-Pit TSFs Parameter Surface TSF In-Pit TSF Containment system Engineered embankment dams Natural rock mass Stored potential energy High Low Failure consequence Severe / catastrophic Limited / localized Dependence on active controls High Moderate Closure complexity High Reduced Alignment with GISTM Conditional Strong The comparison demonstrates that In-Pit TSFs achieve a structural reduction in catastrophic risk by eliminating elevated dams and minimizing stored water volumes, which are dominant contributors to tailings facility failures (Morgenstern et al., 2016). 6.2 Quantitative Risk Evaluation Results Quantitative and semi-quantitative risk evaluations indicate consistently lower risk ratings for In-Pit TSFs across credible failure modes. Using Equation (7), both probability and consequence terms are reduced relative to surface TSFs: • is reduced due to confinement and limited runout potential • is reduced through staged deposition and improved water control Risk matrices place In-Pit TSFs within low to moderate risk categories, while surface TSFs frequently occupy high or extreme risk categories under comparable conditions. 6.3 Failure Modes and Mitigation Effectiveness A structured Failure Modes and Effects Analysis (FMEA) was conducted to identify credible failure mechanisms and assess mitigation effectiveness. Table 5. Principal failure modes and mitigation measures for In-Pit TSFs Failure mode Primary cause Mitigation strategy
RkJQdWJsaXNoZXIy MTM0Mzk2