Investigation of the Macro-Meso Seepage Failure Characteristics of Tailing Sand and Seepage Stability of Tailings Dam in Makeng Mine, Fujian, China

This research aims to study the seepage failure characteristics of the tailing sand, as well as the seepage stability of the tailings dam in the Makeng mine, Fujian, China. Combining with post-test X-ray computed tomography, a macroscopic seepage test was employed to reveal the macro-meso seepage failure mechanism of the tailing sand. The three-dimensional (3D) model was used to analyze the seepage and safety stability of the tailings dam. Results show that the pore and particle changes of tailing sand are greatly affected by the seepage. Along the seepage direction, the migration of the 0–40 μm fine particles leads to the separation of the large pores into small pores with a diameter of 0–40 μm, which reduces the connectivity of the pores. The pore abundance values gradually converge to 0–0.6, and the pore shape becomes elongated. Furthermore, numerical studies show that the depth of the tailings dam's saturation line meets the specified requirements at both the existing and designed elevations. The tailings dam's shear displacement moves in horizontal space and develops downstream along the dam axis. Piping failure may occur on the tensile failure area of the tailings dam surface, and the shear zone near the foundation dam is likely to occur flowing soil failure at the designed elevation.