Abstract: Band Aiming at low-cost utilization of solid and liquid wastes subsequent to mining and beneficiation in underground solid potash mines, laboratory uniaxial compression tests and electron microscope scanning were conducted on tailings-brine mixed consolidation samples under various concentrations of brine and solid-liquid ratios. This study analyzed the mechanical properties, failure characteristics, and macroscopic and microscopic structural changes of the solid-liquid tailings waste filling body. It identified the quantitative impact of brine concentration and solid-liquid ratio on the strength and failure mode of the mixed material. Furthermore, the particle flow discrete element software was used to invert the failure modes of the samples, revealing the fracture development patterns and the failure process of the samples. A damage constitutive model suitable for tailings-brine crystalline consolidation bodies was constructed. The research shows that the structural characteristics, strength properties, and failure modes of the tailings-brine consolidation bodies are influenced by the brine concentration and brine-salt ratio, with the brine-salt ratio being the absolutely dominant factor. The brine-salt ratio significantly alters the distribution characteristics of microcrystals and pores. During the common-ion effect and dissolution-crystallization cycles, high-concentration, low brine-salt ratio samples exhibit MgCl₂ crystals filling the pores between NaCl tetrahedral crystals, forming an interlocking crystalline structure. Both the peak strength and elastic modulus of the samples increase sharply as the brine-salt ratio decreases, while increasing the brine concentration only results in a slight enhancement. When the brine concentration is 30% and the brine-salt ratio is 1∶5, the peak strength of the consolidation body reaches 2.50 MPa. As the brine-salt ratio decreases, the failure mode of the consolidation body transitions from splitting tensile failure to tensile-shear composite failure, ultimately leading to plastic shear failure. Consolidation bodies with a high brine-salt ratio (1∶2) exhibit splitting tensile failure, forming split cracks along the axis that penetrate the entire sample. Consolidation bodies with a low brine-salt ratio (1∶5) exhibit microfracture development and relative displacement on the upper and lower end faces, gradually evolving into a plastic shear zone with a failure angle of 40° to 50° and an extension length of approximately 130 mm. A segmented damage constitutive model for solid-liquid tailings waste consolidation bodies in solid potash mines was constructed, which effectively replicates the elastic deformation process of the consolidation bodies and accurately describes the trend of post-peak stress-strain relationships. This lays the foundation for the development of low-cost cemented filling materials and supporting filling technologies for solid potash mines.