<p>The phase transition characteristics of tailings slurry have a significant impact on the diffusion mechanism of tailings slurry during long-duration grouting. To investigate the diffusion mechanism of tailings slurry in porous media, a Bingham rheological constitutive model was proposed, based on the previous Bingham rheological model, in which both viscosity and yield stress change with time. The rheological properties of the slurry at different temperatures and water-cement ratios were measured through laboratory experiments, and a phase transition constitutive equation was established. Considering the phase transition process of the slurry and the characteristics of the porous media, the diffusion equation of the tailings slurry was derived. Simultaneously, grouting simulation experiments were conducted to verify the correctness of the aforementioned diffusion theory and to obtain the grouting pressure-time development relationship. The results show that under different conditions, the shear stress-shear rate relationship of the slurry conforms to the Bingham constitutive model, with a coefficient of determination exceeding 0.95. The yield stress and viscosity of the slurry increase with increasing temperature and decreasing water-cement ratio. The trends of yield stress-time and viscosity-time changes both satisfy a quadratic function relationship. The water-cement ratio has a greater influence on the rheological properties of the slurry than temperature. Compared with the results of grouting simulation tests, the overall error of the Bingham rheological model theoretical calculation results, in which both yield stress and viscosity change with time, is controlled within 10%. During the grouting process, the pressure-time relationship of tailings slurry in porous media shows a clear “two-stage” growth trend.</p>