Groundwater table of slopes with horizontal drains and effect of pipe inclination

The complex three-dimensional (3D) geometry of the groundwater table (GWT) profile of a slope with horizontal drains (HDs) demands complex 3D numerical simulations to capture the complete effect of HDs on slope stability enhancement. Alternatively, a novel semiempirical method is proposed in this study to obtain the steady state GWT profile of a slope with HDs subjected to constant recharge from the top. As HD pipes are generally installed with an inclination to facilitate drain out under gravity, the proposed method was subsequently extended for inclined HDs and verified by a numerical case study. Although a high pipe inclination is favorable for rapid discharge of water, that will reduce the slope stability enhancement. The results of this study showed that the inclination of the HDs should be kept minimum, especially in the presence of slip surfaces with mild inclinations.