3D Numerical Simulation of the Shortest Length of a Blocking Section for a Self-Starting Drainage Method

This study proposes an innovative landslide management method that achieves autonomous groundwater drainage on slopes. The approach incorporates grouting in the upper part of the inclined siphon drainage borehole, forming a blocking section. A case study demonstrates that the self-initiated drainage system effectively facilitates slope drainage. Additionally, a three-dimensional (3D) numerical model of the seepage field for slopes with borehole structures is established. Based on the model, a methodology for determining the shortest length of the blocking section in self-initiated drainage systems is developed. Applying this method, the shortest blocking section length for the Jiangshan landslide is calculated as 7 m. The results indicate that increasing the total borehole length from 9 to 15 m reduces the required blocking section length from 8 to 7 m, while increasing the borehole inclination from 5° to 25° increases the minimum blocking section length from 7 to 9.8 m. The analysis reveals that changes in the catchment drainage section and grouting blocking section alter local soil permeability, thereby influencing the seepage field and slope stability. Moreover, increasing the soil permeability coefficient from 1 × 10−5 to 1 × 10−3 cm/s reduces the water head at the borehole bottom by 1.525 m and enhances the slope safety factor by 0.106.