# Numerical Simulation of Seepage Surface and Analysis of
## 3 Results
### Analysis of Three-Dimensional Seepage Field at a Dam Height of 210 m  
The fitted permeability coefficients were used to perform a three-dimensional seepage field interaction analysis under complex conditions of multiple gullies at a dam height of 210 m. Three-dimensional seepage analyses of the tailings dams were carried out under normal and flood conditions, resulting in the distribution pattern of total pressure head, the location of the spatial phreatic surface, and the influence of multi-gully pooled seepage on the phreatic surface under different conditions. The total pressure head distribution cloud atlas for the tailings dam is shown in Figure 5 and the spatial phreatic surface distribution cloud atlas for the dam is shown in Figures 6 and 7. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Materials** & **Density (KN/m3)** & **Penetration Coefficient (cm/s)** \\ \hline Starter dam & 21.0 & \(1.50\times 10^{-1}\) \\ Fine sand tailings & 17.9 & \(7.24\times 10^{-4}\) \\ Silty sand tailings & 19.4 & \(5.27\times 10^{-4}\) \\ Silt tailings & 20.1 & \(2.51\times 10^{-4}\) \\ Silty clay tailings & 19.9 & \(0.62\times 10^{-4}\) \\ Decayed rock & 22.0 & \(2.02\times 10^{-6}\) \\ Bedrock & 27.0 & \(3.10\times 10^{-6}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Best solutions of the permeability coefficient for the tailings dam. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Borehole Number** & **ZK1** & **ZK2** & **ZK3** & **ZK4** & **ZK5** & **ZK6** & **ZK7** & **ZK8** & **ZK9** \\ \hline Measured depth of phreatic line/m & 25.9 & 35.5 & 35.8 & 33.2 & 32.8 & 33.3 & 33.9 & 32.1 & 32.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Measured depth of phreatic line in different boreholes. Figure 5: Distribution of total head. (**a**) Normal water-level condition. (**b**) Flood-water-level condition. Figure 6: Map of the location of the phreatic surface under normal water-level conditions (the middle part of the red and blue junction is the location of the phreatic surface of the dam). (**a**) The spatial phreatic surface. (**b**) The phreatic line of the dam body in a typical profile. In Figure 5, different colors represent different values of the total pressure head. The values from largest to smallest are represented by red-to-blue colors, respectively. The red area is mainly found in the reservoir area, indicating that the area, all of which is under water, is a saturated area. In Figures 6-8, the blue area represents the part above the phreatic surface, which is a non-saturated area. The red area represents the part below the phreatic surface, which belongs to the fully saturated region. The green area is located on the interface of the red and blue colors and represents the phreatic surface, and its head pressure value is 0 m. Figures 6b and 7b show the location of the phreatic line for four typical sections for each condition. Section 2-2 passes through the first main ditch, Section 4-4 passes through the third main ditch, and Sections 1-1 and 3-3 pass through the intersection of the two main ditches. According to the analysis results, it can be seen that:  
1. The total head value decreased gradually from upstream to downstream. Taking the flood condition as an example, the maximum value of the upstream head was 1300 m and the minimum value of the downstream head was 1060 m, which was in accordance with the engineering law. The distribution pattern of the total pressure head in the flood condition was basically consistent with that in the normal water-level condition, but the overall distribution increased slightly in the direction of the starter dam, mainly because the length of the beach width in the flood condition was smaller than the length of the dry beach in the normal water-level condition. 2.