Effect of Geobags on Water Flow through Capillary Barrier System

Abstract

Capillary barrier is a two-layer cover system consisting of fine over coarse materials designed to protect slope from rainfall-induced failure. Previous studies have shown that the capillary barrier system (CBS) is effective for protection of gentle slopes, but the application of CBS on steep slopes requires further study. The fine materials are wrapped with geobags before laying them on top of the coarse materials. In this case, the bags serve as the separator between the fine and coarse materials. This paper highlights the effect of geobags on the effectiveness of CBS consisting of fine sand (Sand) as the fine material and reclaimed asphalt pavement (RAP) as the coarse material. Soil column tests were performed for two configurations (1) Sand overlying RAP (no-geo) and (2) Sand overlying RAP with geobags inserted at the interface (geo). The soil column was instrumented with tensiometer-transducer system, moisture sensors and electronic balance to measure pore-water pressures (PWP), volumetric water content (VWC) and outflow, respectively. Numerical simulations were carried out to support the findings from the soil column tests. Results of the soil column tests and numerical analyses on both configurations showed that the presence of geobags at the interface of Sand and RAP does not affect the effectiveness of CBS as slope protection from rainfall infiltration.