Influence of Geogrid-Geotextile Reinforcement on Field-Derived Soil-Water Characteristic Curves and Climate-Driven Moisture Dynamics of Compacted Clay Slopes

Abstract

Geosynthetic reinforcement is widely used to improve slope stability; however, its association with soil–water characteristic curve (SWCC) behavior under natural climatic exposure remains insufficiently understood. This study compared two geometrically identical outdoor reduced-scale compacted-clay slope models: one containing three geogrid-integrated geotextile layers and one unreinforced control. Sensors at a depth of 0.46 m recorded volumetric water content (VWC) and matric suction at 15-min intervals. Drying-path van Genuchten curves were evaluated over the common reliable suction domain of 5.0–51.1 kPa using a trailing 24-h classification and 2000 paired calendar-day bootstrap resamples. The reinforced curve remained above the control curve throughout this domain. The median reinforced-minus-control VWC difference decreased from 0.0454 m3/m3 at 5 kPa (95% conditional interval: 0.0351–0.0590) to 0.0126 m3/m3 at 51.1 kPa (0.0074–0.0180). This difference persisted across 182 sensitivity configurations, although individual model parameters were weakly identifiable. Across 21 rainfall events of at least 5 mm, the reinforced model exhibited smaller median VWC increases and suction decreases. These results provide quantitative benchmarks for interpreting and modeling hydraulic responses in reinforced clay systems. Because only one model represented each configuration and mechanical performance was not measured, the findings are conditional and do not establish a replicated reinforcement effect or improved slope stability.