Analytical and Numerical Stability Analysis of Underground Pillars Subjected to Shear Loading: A Case Study of the Chaabet El Hamra Zinc Mine, Algeria

This study aims to investigate the stability of rooms and pillars along the inclined zinc orebody at the Chaabet El Hamra underground mine (Setif, Algeria). Stability was initially assessed using an analytical shear strength model, with the results subsequently validated through numerical modeling. Geomechanical characterization revealed low interstitial porosity, strong to very strong uniaxial compressive strengths ranging from ۵۰.۴ MPa to ۱۲۹ MPa, and significant fracture-related secondary porosity. Rock Mass Rating (RMR۸۹) and Geological Strength Index (GSI) values suggest fair to good rock quality. The mine design features square pillars inclined at ۱۰°, with walls originally oriented perpendicular to the orebody dip, measuring ۵ m in width and ۳ m in height. The rooms, situated under a cover depth of ۱۴۵.۳ m, are ۹ m wide. This configuration yielded an effective extraction rate of ۸۷.۲۴% and a safety factor of ۱.۶۳, indicating stable mining conditions. Phase ۲D finite-element simulation confirmed these findings, showing a maximum displacement of ۳.۹۶ mm, surface subsidence of ۰.۵۷ mm, and a safety factor of ۱.۶۶, suggesting minimal environmental impact and long-term stability. Shear/compressive stress results from tributary area theory, aligning with numerical results and validating both approaches for inclined orebodies. Finally, the pillar walls, originally perpendicular to the orebody dip, were modified to be vertical relative to the horizontal plane, while maintaining the same pillar and room dimensions and cover depth. This adjustment improved stability by enhancing stress distribution and pillar core confinement, increasing the safety factor to ۱.۸۵.

کلیدواژه ها:

Extraction rate ، Inclined pillars ، Safety factor ، Analytical model ، Numerical Modeling