1033 Where: • L3= probability of failure • s3= consequence of failure In-Pit TSFs inherently reduce s3due to their negative relief geometry and confinement within competent rock mass, while controlled deposition and water management reduce L3. 5.5 Multi-Criteria Decision Analysis (MCDA) Final selection of an In-Pit TSF alternative is supported by a Multi-Criteria Decision Analysis (MCDA) incorporating technical, environmental, social, and economic factors. A decision index OZis calculated as: OZ =C2) $ )/! ⋅ J) (8) Where: • 2)= weighting factor for criterion T • J)= normalized score for criterion T 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: • s3is reduced due to confinement and limited runout potential • L3is reduced through staged deposition and improved water control
RkJQdWJsaXNoZXIy MTM0Mzk2