Unsaturated soil–geotextile interface behavior

The behavior of mechanically stabilized earth (MSE) structures under seasonal climatic variations, i.e. wetting and drying, is not well understood. Stability and serviceability of MSE walls and embankments can significantly depend on the soil-reinforcement (e.g., geosynthetics) interface shearing behavior in unsaturated conditions. This is especially true for reinforced soil slopes and embankments that have significant fines contents. This paper presents results of a laboratory study on the mechanical behavior of unsaturated soil-geotextile interfaces using a specially modified direct shear apparatus. Several suction-controlled laboratory tests were conducted to investigate the effect of soil suction on the soil-geotextile interface. Results of the study indicate that the peak shear strength of the soil-geotextile interface increases nonlinearly with the soil suction. On the other hand, while inconclusive, the effect of suction on the post-peak shear strength of the interface was negligible in some cases. An elastoplastic constitutive model was used to simulate the laboratory results. This study demonstrates that the constitutive model is capable of capturing the mechanical behavior of the unsaturated soil-geotextile interface subjected to constant suction. Both shearing and volume change responses were reasonably simulated by the model.