## 3 Results and Discussion
### Results of Numerical Simulation
It should be noted that the division of the time periods of the three stages is not very accurate, and the purpose is mainly to facilitate the description of the pore pressure development mode in the seepage field of the tailings pond. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Annual Rainfall (mm)**} & \multirow{2}{*}{**Case**} & \multicolumn{3}{c}{**Pore Pressure (kPa)**} \\ \cline{3-5}  & & **Point A** & **Point B** & **Point C** \\ \hline \multirow{3}{*}{400} & Case II-a & 86–86.2 & 106.8–107.2 & 74.6–75.2 \\  & Case II-b & 86.7–86.9 & 108.4–108.8 & 76.5–76.9 \\  & Case II-c & 85.5–85.9 & 105.5–105.9 & 72.9–73.4 \\ \hline \multirow{3}{*}{800} & Case II-d & 131.9–132.3 & 188.3–188.5 & 154.2–154.8 \\  & Case II-e & 131.3–131.7 & 187.3–187.4 & 153.2–154.0 \\ \cline{1-1}  & Case II-f & 131.6–132.1 & 187.9–188.1 & 153.2–154.5 \\ \hline \multirow{3}{*}{1200} & Case II-g & 165.9–166.7 & 252.4–253.4 & 225.3–230.2 \\  & Case II-h & 168–169 & 257.3–258.7 & 230.4–236.2 \\ \cline{1-1}  & Case II-i & 169.8–171.5 & 260.4–262.6 & 235.8–241.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Pore pressure variation range at each point in 50–150 years (kPa). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Annual Rainfall (mm)**} & \multirow{2}{*}{**Case**} & \multicolumn{3}{c}{**Pore Pressure (kPa)**} \\ \cline{3-5}  & & **Point A** & **Point B** & **Point C** \\ \hline \multirow{3}{*}{400} & Case II-a & \(-\)49–83.7 & \(-\)49–101.2 & \(-\)49–65.8 \\  & Case II-b & \(-\)49–84.3 & \(-\)49–102.2 & \(-\)49–67.6 \\  & Case II-c & \(-\)49–83.3 & \(-\)49–100.3 & \(-\)49–64.6 \\ \hline \multirow{3}{*}{800} & Case II-d & \(-\)49–128 & \(-\)49–180.3 & \(-\)49–147.6 \\  & Case II-e & \(-\)49–127.3 & \(-\)49–179.1 & \(-\)49–146.4 \\  & Case II-f & \(-\)49–127.7 & \(-\)49–179.8 & \(-\)49–147.1 \\ \hline \multirow{3}{*}{1200} & Case II-g & \(-\)49–165 & \(-\)49–248.5 & \(-\)49–222.4 \\  & Case II-h & \(-\)49–167 & \(-\)49–253.9 & \(-\)49–228.7 \\ \cline{1-1}  & Case II-i & \(-\)49–169 & \(-\)49–257.4 & \(-\)49–233.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Pore pressure variation range at each point in 0–20 years (kPa). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Annual Rainfall (mm)**} & \multirow{2}{*}{**Case**} & \multicolumn{3}{c}{**Pore Pressure (kPa)**} \\ \cline{3-5}  & & **Point A** & **Point B** & **Point C** \\ \hline \multirow{3}{*}{400} & Case II-a & 83.7–86 & 101.2–106.8 & 65.8–74.6 \\  & Case II-b & 84.3–86.7 & 102.2–108.4 & 67.6–76.5 \\  & Case II-c & 83.3–85.5 & 100.3–105.5 & 64.6–72.9 \\ \hline \multirow{3}{*}{800} & Case II-d & 128–131.9 & 180.3–188.3 & 147.6–154.2 \\  & Case II-e & 127.3–131.3 & 179.1–187.2 & 146.4–153.2 \\ \cline{1-1}  & Case II-f & 127.7–131.6 & 179.8–187.9 & 147.1–154.5 \\ \hline \multirow{3}{*}{1200} & Case II-g & 165–166.5 & 248.5–252.4 & 222.4–225.3 \\ \cline{1-1}  & Case II-h & 167–169 & 253.9–258.7 & 228.7–234.2 \\ \cline{1-1}  & Case II-i & 169–171.5 & 257.4–262.5 & 233.9–239.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Pore pressure variation range at each point in 20–50 years (kPa). Stage 1: Under the action of rainfall, the pore pressure increases relatively fast in the early stage, and the growth values of pore water pressure at each point in this stage are shown in Table 2.  
In this stage, the pore water pressure at the bottom of the tailings pond changes from negative to positive, indicating that the saturation line of the tailings pond has been formed in this stage. In Figure 4a, for different rainfall patterns, the positive pore water pressure first appeared at points A and C when the rainfall lasted 4.75 years, while point B remained negative. This indicates that the saturation line began to appear, but there was no complete saturation line in the dam, due to the different thicknesses of tailings in the dry-stack tailings pond.