Hydraulic behaviour of soil–geocomposite layers in slopes

The behaviour of initially unsaturated soil–geocomposite layers in slopes subject to infiltration is investigated using numerical experiments. The post-infiltration performance is also studied. A series of transient finite element analyses of soil–geocomposite layers is conducted for a variety of soils, slopes and infiltration rates. The influence of these variables on the effectiveness of geocomposites as a drainage material and as a capillary barrier is discussed. The effect of entrapped air within a geotextile is also examined. This study shows that the geocomposite drains more water with a decrease in slope angle and an increase in infiltration rate (i.e. the geocomposite works as a capillary barrier for smaller infiltration rates and steeper slope of the soil–geocomposite layers). It is also shown that the soil immediately above the geocomposite becomes wet before the geocomposite starts draining water, and it remains wet for a relatively long period of time after the infiltration event.