Large cell triaxial tests of a partially saturated soil with vegetation

Fraccica Alessandro, Romero Enrique, Fourcaud Thierry. 2023. Large cell triaxial tests of a partially saturated soil with vegetation. In : 8th International Conference on Unsaturated Soils (UNSAT 2023). Bardanis M. (ed.). Les Ulis : EDP Sciences, 1-6. (E3S Web of Conferences, 382) International Conference on Unsaturated Soils (UNSAT 2023). 8, Milos, Grèce, 2 Mai 2023/5 Mai 2023.

https://doi.org/10.1051/e3sconf/202338205005

Communication avec actes ; Article de recherche

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Résumé : The use of vegetation roots as a nature-based solution against landslides and erosion requires the definition of sample preparation protocols and adoption of equipment that allows testing representative elementary volumes of the whole soil-root system. For this purpose, large cell triaxial compression tests were carried out on fallow and vegetated samples at different degrees of saturation. Samples were prepared by static compaction of a silty sand and seeded with Cynodon dactylon. The hydraulic state during plants growth was controlled and reproduced on bare soil samples. After isotropic compressions, the shearing phase was carried out at very low confining stresses (i.e., below 50 kPa). Tests were deemed to be comparable by assessing the normalised volume of roots with respect to soil, after shearing. For a given confining stress, soil samples with higher matric suction exhibited higher shear strength, furtherly increased by roots. The stress-strain behaviour observed in the vegetated soil systematically changed, when comparing tests at low and high matric suction values, due to the different mechanisms of vegetation reinforcement depending on the hydraulic state at the soil-root interface. The results were successfully interpreted within a failure criterion and skeleton stress framework for partially saturated soils, considering soil suction, degree of saturation, soil microstructure and the normalised volume of roots.

Mots-clés libres : Soil mechanics, Roots, Soil erosion

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