Numerical simulation of wicking nonwoven geotextiles embedded in unsaturated soil subgrade

Excess moisture in unsaturated subgrade layers is a primary cause of long-term deterioration in transportation embankments, leading to reduced soil stiffness and degraded performance under environmental and traffic loading. Conventional drainage systems, including traditional geotextiles, are ineffective in partially saturated soils governed by negative pore-water pressures. Recently developed wicking nonwoven geotextiles provide a promising alternative because they transmit water under both saturated and unsaturated conditions through capillary action. This study presents a numerical investigation of transportation embankments incorporating a wicking nonwoven geotextile. A finite element model based on Richards’ equation is developed to simulate unsaturated flow and is validated using laboratory column tests that reproduce soil capillary-rise behavior. The validated model is extended to full-scale embankment simulations to evaluate geotextile performance. The analyses consider two rainfall intensities, moderate and heavy, two soil types (sand with 23.4% silt and sand with 8.8% silt), and installation configurations including single- and multilayer applications. Water content and matric suction distributions are analyzed to quantify geotextile control of moisture migration. Changes in average resilient modulus are estimated using an empirical MEPDG relationship to assess the potential stiffness implications of moisture reduction. Results show that the wicking nonwoven geotextile reduces moisture under unsaturated conditions. The direct wicking depth of a single layer ranges from approximately 10 to 25 cm below its installation level, depending on soil type and embankment location, while the broader VWC influence zone can extend through the full 0.5 m embankment depth. Based on the MEPDG relationship, the estimated average resilient modulus increases by approximately 15% to 70%, indicating the potential benefit of wicking geotextiles for mitigating moisture-related deterioration in transportation embankments.