A Numerical Investigation of Drainage Characteristics of Nonwoven Geotextile in Unsaturated Fine-grained Soil

Abstract

This study presents a comprehensive numerical investigation into the drainage behavior of nonwoven geotextiles embedded within unsaturated fine-grained soils. The simulations were calibrated using laboratory data to ensure consistency and reliability. Transient seepage analyses were performed to evaluate the dual functionality of geotextiles-as capillary barriers and drainage layers-under varying infiltration conditions. The study examined geotextile performance in both lateral and vertical drainage configurations, considering the presence or absence of vertical drains, and evaluated behavior under varying initial soil moisture contents and successive wetting-drying cycles. Results demonstrate that geotextiles act as effective capillary barriers, delaying water migration until a breakthrough suction is reached. The time to breakthrough was found to depend strongly on the geotextile’s hydraulic properties and the initial moisture content of the surrounding soil. The study also showed that geotextiles maintain lower suction values in the subsurface, even after prolonged drying periods. A parametric analysis involving seven geotextile types revealed that air-entry suction is a critical factor governing lateral drainage performance. Geotextiles with higher air-entry or water-entry suction values facilitated quicker breakthroughs and more efficient drainage. Overall, this research provides valuable insight into the hydraulic mechanisms governing geotextile behavior in unsaturated conditions and underscores the importance of incorporating unsaturated soil-geotextile interactions into drainage system design.