Integrated Stability Assessment of Mine Tailings under Static and Seismic Conditions: Application of Limit Equilibrium Methods and Eurocode 7 to the Auzelles Site (France)

Résumé fourni par la source

The instability of mine tailings represents a major environmental and geotechnical challenge, particularly due to the risk of slope failure and contamination of surrounding watercourses. At the Auzelles site (Auvergne, France), the absence of prior stability assessment combined with steep natural slopes (35°–40°) constitutes a critical factor of instability. This study aims to evaluate the stability of slag heap 1 by analyzing the influence of slope geometry under both static and pseudo-static conditions. The methodology is based on limit equilibrium analysis using Talren software, with the simplified Bishop method, in accordance with both the traditional approach and the EN1997-1 Eurocode 7 framework. Two representative cross-sections were analyzed before and after earthworks. The analysis assumes free-draining tailings conditions, with no pore water pressure considered. The results show that the initial state of the slopes is unstable, with safety factors of 1.07 under static conditions, 0.89 under pseudo-static conditions, and 0.78 using the Eurocode approach, indicating a high risk of failure. After slope regrading to 27°, a significant improvement in stability is observed. The safety factors increase to 1.42–1.44 under static conditions, 1.11–1.15 under pseudo-static conditions, and 1.03–1.05 using the Eurocode approach, satisfying the required stability criteria. These results demonstrate that slope geometry is the primary controlling factor of stability at the site, and that reprofiling significantly enhances safety conditions. The study confirms the effectiveness of combining traditional and normative approaches for reliable stability assessment and highlights the importance of considering both static and seismic conditions in the long-term management of tailings storage facilities.