## 3 Microscopic Characterization of Tailings Particles
### Microstructure Characterization  
In the two-dimensional characterization of microscopic particles, [PERSON] [14] believes that there are three independent properties, namely, the description of the overall contour (roundness) of the particle, the description of the smoothness of the edges and corners of the particle (convexity), and the description of the surface texture (roughness) of the particle. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Numbering** & **Calculated Porosity (\%)** & **Measured Values (\%)** & **Relative Error** \\ \hline CLT & 27.73 & 28.38 & 2.34 \\ FCT & 31.78 & 32.34 & 1.76 \\ SCT & 33.64 & 32.86 & 2.32 \\ STT & 40.08 & 38.49 & 3.97 \\ SDT & 48.25 & 50.13 & 3.90 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Porosity of each specimen. Figure 8: Profile of porosity along height. Figure 7: **(a)** Grayscale graph, **(b)** threshold segmentation, **(c)** local segmentation, **(d)** the two are jointly identified, **(e)** the two are combined to extract the pores. The characterization of tailings' particle morphology is the key to the characterization of the tailings' microstructure, and its roundness can be described by the form factor \(F_{\text{S}}\). The form factor is the ratio of the perimeter of the particle boundary to the circumference of a circle of the same area as the particle, which will directly affect the accumulation characteristics of the tailings, change the porosity and permeability path of the tailings, and most importantly, it is closely related to the shear strength of the tailings. It can be calculated according to Equation (3) [15]. \[F_{\text{s}}=\frac{P}{2\pi r} \tag{3}\]  
where \(P\) is the perimeter of the particle; \(r\) is the equivalent radius. According to Equation (3), the shape factor of the circle is 1.0, and it can be seen that the closer the shape factor value is to 1, the closer the particle is to a circle, and the roundness reflects the degree to which the overall contour of the particle is close to a circle. Taking the CLT sample as an example, the histogram of its frequency distribution and the trend change plot are shown in Figure 9.  
As can be seen from Figure 9, the shape factor of the tailings particles is mainly distributed between 0.8 and 1.1, and the particles in this interval are more than 90%. It can be seen that the two-dimensional morphology of particles is mainly approximate to an ellipse. A comprehensive comparison of viscous tailings, silty tailings and sandy tailings shows that the circularity will decrease slightly with the increase in tailings particle size, but the overall situation is relatively stable, with the value ranging from 0.7 to 1.1, and the average value is maintained around 0.875. The parameters for characterizing the morphological size of the particles are shown in Table 5, and the particles are analyzed and calculated according to the parameters listed in the table. A schematic diagram of the structure of the characterization of physical parameters is shown in Figure 10. \begin{table}
\begin{tabular}{c c} \hline
**Parameter** & **Descriptions of the Meanings of Various Parameters** \\ \hline \(S_{1}\) & The actual area of the particles \\ \(P_{1}\) & The actual perimeter of the particle \\ \(F_{\text{max}}\) & The maximum distance between parallel lines tangential to the outer edge of the particle \\ \(F_{\text{min}}\) & The minimum distance between parallel lines tangential to the outer edge of the particle \\ \(S_{2}\) & The area of the external polygon along the particle boundary \\ \(P_{2}\) & The perimeter of the circumscribed polygon along the particle boundary \\ \(d\) & The diameter of a circle with the same area as the particle \\ \hline \end{tabular}
\end{table} 
Table 5: Basic size parameters of particle morphology. Figure 9: Shape factor distribution and trend change chart. (**a**) Distribution histogram; (**b**) change in shape factor of tailings.