Effect of Horizontal Drain Installation Pattern on Drainage Performance and Slope Stability

Horizontal drains (HDs) play a vital role in improving the stability of slopes prone to rain-induced failures. The installation pattern of HDs is a crucial factor in optimizing the slope stability enhancement. In this study, a series of numerical model analyses was conducted to assess the impact of HD arrangements, with specific emphasis on drains at higher elevations. This study evaluates the hydraulic and stability condition of the slope, as well as the discharge behavior of the HDs during and after the rainfall events. The results showed that high-intensity short-duration rainfall events are more critical than the low-intensity long-duration rainfall events. While the HDs located at lower elevations exhibit a higher effectiveness, the efficiency of the upper-level HDs rises with the increasing rainfall intensity. Consequently, the selection of an appropriate HD arrangement should be based on a comprehensive understanding of the expected critical rainfall events.