Modeling of Permeability Coefficient Calculations Based on the Mesostructure Parameters of Tailings

The permeability coefficient of tailings in tailings ponds, which can affect the release and migration of heavy metals in tailings, also affects the stability of dams by affecting the variation of the height of the saturation line. In this paper, tailings at different levels in a tailings pond were taken as research objects to measure the particle size and permeability coefficient of the tailings. At the same time, CT scanning technology and three-dimensional reconstruction were used to establish the three-dimensional model of the tailings, and the permeability coefficient of the tailings was analyzed from a mesostructural point of view. The results show the following: (1) The particle size of the tailings in the tailings pond decreased rapidly with the increase of distance from the discharge port. When the distance exceeded 8 m, a sudden change occurred, and the decreasing trend obviously slowed down. The particle size of tailings decreased, the compactness increased, and the permeability coefficient decreased gradually. (2) Statistics and analysis of the mesostructure affecting the permeability coefficient of tailings: the error between the calculated value and the measured value of the particle size and porosity of the three-dimensional reconstruction model was small, which proved that the model had high reliability. The porosity, sphericity, and particle size of the tailings were consistent and decreased with the increase of distance from the discharge port. The number of pore branches and nodes of the tailings increased with the increase of the distance from the discharge port, while the average radius and length of the pores decreased. The fragmentation index can characterize the pore channel connectivity of the tailings, which has a high negative linear correlation with the number of pore branches and a positive quadratic curve correlation with the average branch length of the pores. (3) Based on the Kozeny-Carman equation and data regression analysis method and combined with the results of permeability coefficient measurements, the fragmentation index was introduced into the Kozeny-Carman equation. Also, a modified model for calculating the permeability coefficient of the tailings was established based on the mesostructure parameters. By comparing the measured values of the tailings' permeability coefficient, the error range was 1.91-13.24%. The research results have important theoretical significance for the prevention and control of heavy metal pollution and the stability of tailings ponds.