Experimental investigation of the capillary drainage performance of multilayer wicking fabric

Excessive moisture within subgrade layers significantly diminishes subgrade stiffness and induces pavement deformation. A multilayer wicking fabric (WF) composed of deeply grooved fibers was developed to regulate moisture in unsaturated fine-grained soils. This study introduces a novel methodology for determining the water retention curve (WRC) over the full suction range. At the same time, an efficient method for predicting WF's WRC via NMR technology was pointed, and clarifying the material's microscopic drainage mechanisms. Building on this foundation, soil column drying experiments were conducted to verify WF's moisture regulation capacity in unsaturated fine-grained soils. The results demonstrate that WF exhibits its highest water retention under conditions of elevated matric suction. Additionally, soil column drying experiments reveal that WF incorporation significantly reduces average soil water content and accelerates drying rates. WF's drainage efficiency shows high sensitivity to initial water contents ( w i ) and evaporation segment length ( L ), with drainage performance increasing proportionally to these parameters. Moreover, soil water profiles are influenced by water retention capacity, capillary migration rate, and hydraulic gradient. These findings underscore the potential of multilayer wicking fabrics in managing moisture within fine-grained subgrades, presenting a novel and effective strategy for maintaining subgrade dryness and enhancing long-term stability. • WF drains capillary water from the fine-grained soil. • A novel method for measuring WRC of thin-layer porous materials is proposed. • NMR is applied to fabric structures to reveal microscopic drainage properties. • The key factors and mechanism of WF drainage were clarified.