Research on the Stability of Tailings Dams Under the Combined Stacking of Waste Rock Pillars and Tailings

Tailings dam failures are often caused by seepage, posing severe threats to mine safety and downstream ecological environments. Conventional tailings stacking methods are prone to drainage blockage and slope instability under long-term seepage conditions. To address this issue, this study proposes a novel structural form that combines waste rock pillars with tailings stacking to construct a drainage system characterized by high permeability, anti-clogging capability, and load-bearing performance. A prototype-similar physical model test was conducted to systematically analyze the seepage characteristics and stability variations in the tailings dam under different dry beach lengths. In addition, numerical simulations using Geo-Studio 2022.1 (SEEP/W and SLOPE/W) were performed to verify and extend the experimental results. The findings show that the introduction of waste rock pillars forms effective preferential drainage channels, significantly reduces pore water pressure, and lowers the phreatic line within the dam body, thereby enhancing its overall stability. Compared with the conventional stacking method without waste rock pillars, the safety factor of the dam increased by 8.6–20.0% as the dry beach length extended from 70 m to 150 m, confirming the remarkable reinforcement and drainage performance of the composite structure. The study demonstrates that the proposed “high-permeability, anti-clogging, and load-bearing” waste rock pillar design not only achieves efficient reuse of waste rock resources but also provides a novel and sustainable technical approach for improving tailings dam safety through coupled physical and numerical verification.