# Study on Siphon Drainage Capacity of Slopes with Long-Horizontal Pipe Sections
## 4 Discussion
### Calculation of Slope Drainage Capacity Requirements in Combination with Single-Hole Gushing Water
According to [PERSON]'s research results, this can be directly calculated to obtain the single-hole water influx, as shown in Table 2.  
For slopes, controlling the groundwater level in the slope body below the danger level of the landslide is the primary condition to be met by the drainage system. Therefore, the drainage capacity of the siphon drainage hole needs to meet the condition that when heavy rainfall occurs, the groundwater level caused by the infiltration of rainfall into the slope body cannot exceed the controlled groundwater level after it rises. The amount of rainfall infiltration is related to many complex factors such as topographic conditions, climatic environment, slope size, and geotechnical structure, etc., and cannot be fully quantified for analysis. However, the maximum amount of groundwater infiltration on slopes will not exceed the amount of infiltration when the water table reaches the slope surface. The siphon discharge volume can be calculated from the siphon discharge rate according to the following equation. \[Q=vAt=0.0216\pi d^{2}v\,\left(\mathrm{m^{3}/d}\right) \tag{8}\]  
where \(t\) refers to the time of a day. Then, the single-day drainage capacity of multiple siphons in a borehole is  
\[Q_{dmm}=nq_{dmm}=0.0216\pi d^{2}nv \tag{9}\]  
Figure 13a,b shows surface fits of the drainage capacity for each pipe diameter at different lifts (x-axis--siphon diameter, y-axis--lift, z-axis--discharge) for 30 m and 200 m lengths of siphons, respectively. The siphon discharge capacity of a single short pipe strictly follows the rule \"the larger the pipe diameter, the higher the discharge capacity,\" but the number of siphons placed in the same size borehole is not proportional to the siphon diameter. The surface fit shows that the water-lowering capacity of the short siphon increases with the diameter of the pipe. It is worth noting that the D-6.5 and D-8 siphons do not have long-term application stability and only increase the surface fit's reliability in the MATLAB iterative calculations and are not used as pipe diameters to be considered. Figure 13 shows that peak drainage occurs near the 5.2 mm position, which is determined by the product function of the total cross-sectional area of the siphons lined up in the borehole and the flow rate (i.e., the single-hole drainage). However, as the total length of the siphon increases, the positive relationship between drainage capacity and siphon  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Permeability Coefficient** & **Gushing Capacity** & \multicolumn{3}{c}{**Groundwater Level Drop at the Borehole Bottom (\(s_{w}\))**} \\ \cline{2-5}  & **5 m** & **10 m** & **15 m** & **20 m** \\ \hline \(10^{-3}\) cm/s & 11.27 & 38.44 & 79.64 & 134.05 \\ \(10^{-4}\) cm/s & 1.39 & 4.59 & 9.37 & 15.62 \\ \(10^{-5}\) cm/s & 0.18 & 0.57 & 1.14 & 1.87 \\ \(10^{-6}\) cm/s & 0.03 & 0.08 & 0.14 diameter gradually changes. D-5 siphons perform increasingly well and show a smaller decrease in drainage capacity with changes in pipe length and other factors compared to D-8 pipes. Therefore, the D-5 siphon performs best for all pipe diameters. Based on the factors influencing siphon drainage capacity described in the paper, the borehole diameter and siphon wall thickness are superficially more favorable to process improvement measures in terms of enhancing siphon drainage capacity. However, since the borehole and siphon are circular, the siphon placement problem can be reduced to a geometric problem of \"small circles inside large circles\". According to this equation, the calculated number of placements is a non-exact result applicable to the construction conditions. According to the calculation principle, when the diameter of the borehole increases, the proportional increase in the number of construction placements for each pipe diameter is not unidirectional and linear and may even fluctuate. Therefore, the borehole size can be freely determined according to the project's needs in the actual project.