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.

Mesoscopic Seepage Simulation and Analysis of Unclassified Tailings Pores Based on 3D Reconstruction Technology.

Taking the unclassified tailings as the research object, the three-dimensional (3D) pore model was established using computed tomography (CT) scanning technology, image processing, and the 3D reconstruction method. The model was imported into Flac3D software for mesoscopic seepage simulation and analysis. Combined with the laboratory seepage experiment, the influence of tailings' mesoscopic parameters on permeability was explored. The results show that there is a high correlation between the fractal dimension and fragmentation index of tailings pores and the mesoscopic seepage coefficient, with correlation coefficients of 0.987 and 0.973, respectively. When the porosity difference of the pore model is small, the permeability is mainly affected by pore connectivity. The mathematical model between the permeability coefficient and the fragmentation index of tailings is established. The average error between the permeability coefficient calculated by the model and the measured value is reduced to 4.98%, which proves that the mathematical model has guaranteed reliability.

Temporal-Spatial Distribution of Vehicle Transportation Pavement Dust Migration in an Open-Pit Mine.

To investigate the dust source of the most polluted equipment in the open-pit mine, this paper studied the temporal-spatial distribution laws of dust migration in the vehicle transportation pavements in the open-pit mine via theoretical analysis and a field test. The results show that the dust concentration of the same horizontal distance from the pavement centerline remains roughly stable, which proves that the dust above the pavements is a continuous line source. In the horizontal direction, the maximum dust and baseline concentration reached heights of 1-3 and 20 m away from the wheels, respectively, while they are obtained at heights of 0.5 and 2.2 m away from the pavement in the vertical distance, respectively. The spatial concentration distribution of the dust clearly proves that the dust movement mode is a jumping mode. It takes 6 and 30 s after the vehicle had passed to achieve the maximum dust and baseline concentration, respectively. The dust concentration of a fully loaded vehicle is 2-3 times greater than that of a no-load vehicle. Meanwhile, the dust concentration of a sprinkling pavement is as 10% as that of an un-sprinkling pavement. The results of the migration of transportation dust and temporal-spatial distribution provide useful references for the analysis of dust source intension and pollutant diffusion in open-pit mines. Furthermore, the efficient and low-cost moisturized dust suppressant would be the future direction to develop in different mining areas.