Physical modeling of a drainage system on a layered sandy-clayey slope

The paper investigates the effect of horizontal drains in the prevention of seepage-induced collapse inside a layered slope. In particular, the research carried out using a plane strain 1g physical model, emphasizes the importance of a correct identification of some thin low-permeability layers in a slope, in order to evaluate slope stability and eventually, design a stabilizing drainage system. A sandy slope containing some kaolin layers, was subjected to a transient seepage causing high pore water pressure at the base of the cohesive layers and inducing collapse of the slope. The same testing procedure was repeated after the installation of sub-horizontal drains in the slope with different dip-angles, preventing any increase in water pressure and the consequent collapse. On the basis of experimental results, a FE model was calibrated, which facilitated description of the transient flow, reconstruction of the pore pressure distribution and the evaluation of drain effects on slope stability.