A Numerical Study of Drainage Characteristics of Nonwoven Geotextile on the Performance of a Reinforced Soil Wall Comprising Unsaturated Marginal Backfill

This study presents a numerical investigation of the hydraulic (drainage) and mechanical (reinforcement) characteristics of nonwoven geotextile and its efficacy in the application of geosynthetic-reinforced soil wall comprising fine-grained marginal soil as backfill material. The numerical simulations of rainwater infiltration in unsaturated soil revealed a capillary barrier phenomenon of geotextile, which prevents the progression of saturated wetting front in the marginal soil backfill through the geotextile layers until the attainment of breakthrough suction at each soil-geotextile interface. Each geotextile layer successively functions as a capillary barrier and a drainage medium as the saturated front progresses within the backfill, thus aiding the backfill to preserve greater suction for a longer duration of rainwater infiltration. Local instability in the soil wall is observed due to the accumulation of pore water above the geotextile layers undergoing the capillary barrier action. Sand cushions sandwiching the geotextile layers substantially improved the local and global stability by minimizing the capillary barrier action.