Investigating Hydro-Mechanical Responses of Copper Mine Tailings Dams: Insights from Numerical Simulations of Upstream, Downstream, and Centerline Designs

Understanding the hydro-mechanical behavior of unsaturated tailings dams under cyclic hydrologic loading is essential for preventing dam failures. This study investigates the stability and seepage characteristics of copper mine tailings dams constructed using upstream, downstream, and centerline methods through coupled stress-pore pressure analyses. A comprehensive numerical model was developed incorporating: (1) saturated-unsaturated transient seepage under rainfall infiltration, (2) staged construction loading using limit equilibrium analysis, and (3) method-specific soil-water characteristic curves for drying/wetting cycles. The results demonstrate distinct performance patterns among construction methods. The upstream method showed the greatest vulnerability, with the factor of safety (FOS) declining by 11% (from 1.58 to 1.40) under rainfall infiltration. In contrast, the centerline method maintained superior stability (6% FOS reduction) with rapid pore pressure dissipation. The stresses induced by precipitation were secondary to the stresses due to the increasing height of the dam. The study establishes that method selection fundamentally affects pore pressure development, with an upstream tailings dam with upstream-sloping core creating sustained saturation that reduces effective stress, while downstream construction configuration facilitates efficient pore pressure dissipation through its internal drainage pathways. These insights provide critical guidance for tailings dam design, particularly in high-rainfall regions where pore pressure management is paramount for long-term stability.